Carbon-Supported Noble-Metal Nanoparticles: History
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Contributor:
Agnieszka Karczmarska
,
Michał Adamek
,
Sara El Houbbadi
,
Paweł Kowalczyk
,
Magdalena Laskowska

Noble-metal nanoparticles (NMNPs), with their outstanding properties, have been arousing the interest of scientists for centuries. Although our knowledge of them is much more significant today, and people can obtain NMNPs in various sizes, shapes, and compositions, our interest in them has not waned. When talking about noble metals, gold, silver, and platinum come to mind first. Still, people cannot forget about elements belonging to the so-called platinum group, such as ruthenium, rhodium, palladium, osmium, and iridium, whose physical and chemical properties are very similar to those of platinum. It makes them highly demanded and widely used in various applications. The current knowledge on the preparation of all noble metals is presented in the form of nanoparticles and their assembling with carbon supports.

  • carbon-supported nanoparticles
  • catalysts
  • fuel cells

1. Introduction

To date, noble-metal nanoparticles have been successfully incorporated with polymers [1][2][3], oxides (e.g., SiO2 [4], Al2O3, TiO2 and CeO2 [5] Nb2O5, Ta2O5, and ZrO2 [6]), metal–organic frameworks (e.g., ZIF-8, MIL-101-NH2) [7][8] and carbon materials (e.g., carbon black, carbon nanotubes, graphene) [9][10][11][12]. Over the past decades, carbon materials have been recognized as an ideal substrate because of their extraordinary physical and chemical properties and their universal availability, processibility, environmental friendliness, and relative stability in both acidic and basic media [13]. At this point, it should be added that carbonaceous materials (CMs) have a large specific surface area, high porosity, excellent electron conductivity, relative chemical inertness, good thermal stability under an inert atmosphere, an intrinsic hydrophobic nature, and the presence of vast functional groups that facilitate metal loading [10][14].
Depending on distinct types of crystal structures, carbon atoms can form a variety of allotropes with different properties [15]. In particular, carbon nanomaterials, such as 0D fullerenes, 1D carbon nanotubes, 2D graphene, etc., have dynamized research in the field of electrocatalysis. Built on them, noble-metal nanoparticles (NMNPs)/carbonaceous materials (CMs) nanocomposites are an ideal option for various electrochemical reactions in energy conversion and storage, including hydrogen evolution and oxygen reduction. These materials withstand various types of electrochemical oxidation reactions, which reduce the lifetime of electrocatalysts due to sintering and poisoning effects [16][17].
In conventional systems, carbon black, which is a product produced by the pyrolysis of petroleum hydrocarbons, is usually used as a carrier for Pt nanoparticles. Due to its high availability and low cost, it is widely used in electrocatalysis applications [18]. Common carbon blacks include acetylene black, Vulcan XC-72, Ketjen Black, etc. Their major physicochemical characteristics include specific surface area, electronic conductivity, large surface-to-volume ratio, stability, and surface functionality [19][20][21][22][23].

2. Methods of Obtaining Noble-Metal Nanoparticles/Carbonaceous Materials Nanocomposites

Thus far, a lot of work has been devoted to developing new, efficient methods for the preparation of electrochemically active NMNPs/CMs nanocomposites. It was found that the smaller and more homogeneous the immobilized metal particles are, the better the electrocatalytic properties of the nanohybrid [24][25][26]. Among the chemical-deposition methods of NMNPs on carbonaceous supports, one can distinguish: surface-functionalization methods, electrochemical deposition, and electroless deposition [27][28]. In this research, it has been decided that detailed descriptions of the syntheses of nanocomposites and their catalytic properties are to be presented for the most frequently described, i.e., widely understood, mesoporous carbon materials, carbon nanotubes, and graphene (Figure 1). Examples of other carbon supports along with an indication of the synthesis method are summarized in Table 1.
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Figure 1. A schematic representation of various carbon supports for NMNPs.
Table 1. Examples of carbon-supported nanocomposites categorized by synthesis method.
Synthesis Method Precursors Type of NMNPs NM Particle Size [nm] References
Surface functionalization CNF, NaOH, H2SO4, H2PtCl6 Pt 6 [29]
CNF/TiO2, EG, NaOH, H2PtCl6 Pt 3.8 [30]
Ketjen Black, HNO3, H2PtCl6 Pt 2.5 [31]
N-CNT, HCOOH, H2PtCl6 Pt (nanorods) 3–4 × 10 [32]
Vulcan XC72, HNO3, H2PtCl6 Pt 2.2 ± 0.4 [33]
rGO, HCOOH, H2PtCl6, PdCl2 PtPd 4 × 20–200 [34]
Pt nanowires
Pd nanoparticles 5
Ni-N-CNTs, PDDA, PdCl2 Pd 2–5 [35]
MWCNTs, THF, H2PtCl6, SnCl4 PtSn ~4 [36]
CX, HNO3, H2PtCl6, RuCl3 PtRu 3.8–4.4 [37]
BDD, NaOH, SDBS, RuCl3, H2PtCl6 PtRu 2–5 [38]
rGO, KAuCl4, K2PtCl6 Pt 2.34 ± 0.52 [39]
Pt-Au 2.86 ± 1.30
rGO, Vulcan XC-72, H2PtCl6 Pt 0.5–2.5 [40]
G-CNTs, KOH, H2PtCl6 Pt 4.3–6.8 [41]
rGO, EG, HAuCl4, H2PtCl6 Pt-Au   [42]
CQD, Vulcan XC-72, H2PtCl6, NaBH4 Pt   [43]
N-GQD, Na2CO3, HCl, PdCl2 Pd   [44]
N-GN, CoCl2, RuCl3 RuCo 6.2 [45]
C60, H2PtCl6, Pt <5 [46]
C60, NaOH, H2PtCl6 Pt 3.93–4.20 [47]
GO-PyrC60, PdCl2 Pd 10 [48]
CA, Vulcan XC-72R, H2PtCl6, NaBH4 Pt 3.24 [49]
MNC, CCA, NaOH, H2PtCl6, NaBH4 Pt 3.1 [50]
Vulcan XC-72R, NaOH, H2PtCl6, H2IrCl6 PtIr 3.6–3.9 [51]
CNT, H2SO4, IrCl3 Ir ~1 [52]
MWCNT, EG, HNO3, H2SO4, H2PtCl6, RuCl3, ReCl3 Pt-Ru 2.79 ± 0.58 [53]
Pt-Re 3.53 ± 0.80
Pt-Ru-Re 2.88 ± 0.64
Pt-Ru-Re 2.68 ± 0.55
Pt-Ru-Re 3.19 ± 0.54
Electrochemical deposition CNT, EG, H2PtCl6, RuCl3 Pt-Ru 3.1–5.6 [54]
GO, H2PtCl6, KH2PO4 Pt 10 [55]
GO, CNF, H2PtCl6, H2SO4 Pt 350–500 [56]
CP, H2PtCl6, RuCl3, HCl, KOH Pt-Ru 52.9 ± 9.2 [57]
GR, ZnO, K2PtCl6, H2SO4 Pt 250 [58]
BDD, NaBH4, NaOH, H2PtCl6 Pt 15 ± 5 [59]
BDD, Ni(NO3)2, HCl, PdCl2 Pd ~13 [60]
Vulcan XC-72, H2PtCl6, H2SO4 Pt 1–4 [61]
Electroless deposition CNO, H2PtCl6 Pt 20 [62]
CNT, CoCl2, H2PtCl6 Pt 30–40 [63]
CNT, SDS, EG, Na2PdCl4 Pd 2–5 [64]
MWCNT, HAuCl4 Au 10 [65]
PC, C6H5K3O7, RhCl3, RuCl3, IrCl3 Ir 0.96 ± 0.13 [66]
Rh 1.11 ± 0.31
Ru 1.37 ± 0.39
NiO/Ni/CNTs, K2PtCl6 Pt ~2 [67]
Two types of procedures can be used depending on the requirement. In type 1: previously synthesized metal nanoparticles are deposited on carbon substrates. In type 2: the formation of nanoparticles and their deposition on carbon substrates occurs during a single process. These two processes can be based on the creation of covalent or noncovalent interactions between individual elements of nanocomponents. Both functionalization processes serve to enhance the number of active binding sites for the deposition of metal-nanoparticle catalysts and also to improve the dispersibility of the carbon substrate in water or solvents. These aspects ultimately enhance the catalytic effect [68][69]. In the case of noncovalent functionalization, the hybridization of the material in question remains unchanged. It also has little effect on its electronic properties, as a result of the weak van der Waals forces of attraction between the adsorbates and carbon substrates [27][28][70]. In the case of covalent functionalization, different types of binding sites are generated. One form of covalent functionalization is oxidative means, during which oxygen groups such as carboxyl, carbonyl and hydroxyl groups, are formed [28][71]. They stabilize the dispersion of carbonaceous materials in polar solvents and provide active sites for metal adsorption. Such functionalized carbon materials with noble metal precursors can be further reduced by the addition of reducing agents (e.g., ethylene glycol (EG), NaBH4, H2, formic acid (HCOOH), etc.) to form NMNPs/CMs hybrids [72][73]. The synthesis process can be significantly accelerated by using an irradiation-assisted technique, for example, visible light or microwave irradiation [74][75]. Particularly noteworthy is the microwave-assisted polyol method, which has numerous advantages such as ease of procedure, speed and safety [76][77].
In the electrochemical method, the MNNPs/CMs nanocompounds are obtained via the reduction of noble metal complexes, such as H[AuCl4], H2[PtCl4], or (NH4)2[PdCl4], by electrons. It consists of the following steps: deposition of carbon material on the electrode, immersion of the carbon-coated electrode in an electrolytic solution containing metallic precursors, and application of an electrochemical potential. Carbonaceous materials act as molecular conductors to provide support for the deposited NMNPs. It should be noted that, in this case, CMs do not react with noble metal salts. The nucleation process and subsequent growth of NPs can be effectively controlled by adjusting electrodeposition parameters such as nucleation potential, deposition time, metal salt concentration, etc., [27][28][55][57][78][79].
The electrodeless deposition method constitutes a chemical process involving a direct redox reaction, by electron transfer between metal ions (higher reducing potential), and a carbon support [80][81]. Due to the fact that such a process does not require any external reducing agents, electrodeless deposition is considered as a green strategy for producing metal NPs on carbon substrates [82].

2.1. Noble-Metal Nanoparticles on Mesoporous Carbon Materials

Carbon materials with mesoporous characteristics (2 nm < pore sizes < 50 nm) have received considerable attention in electrocatalytic applications. They can facilitate the transport of reactants to the electrocatalysts and simultaneously exhibit large surface areas and low charge-transfer resistance [83][84][85]. On this basis, numerous examples of the use of mesoporous carbon materials [37][86][87] have attracted much interest as electrocatalyst supports for fuel-cell applications. Using ordered and highly ordered mesopoporous carbon materials as substrates for Pt and PtRu nanoparticles, respectively, it was shown that the size and distribution of mesopores play an important role in electrochemical reactions [87][88]. Qi et al. synthesized PtRu nanoparticles with graphitic mesoporous carbon (GMC) substrates using a chemical reduction process, with H2PtCl6 and RuCl3 as precursor nanoparticles [83]. The study involved the use of GMCs with different pore sizes, and the results clearly indicated that this parameter affects the performance of direct methanol fuel cells. Carbon aerogels (CA), which can be synthesized from cellulosic biomass, are another favorable porous material for fuel-cell-energy-storage and conversion applications [89][90][91][92]. An example is the work of Gu et al., in which the effect of CA pore size on the deposition of Pt NPs was reported for proton-exchange-membrane-fuel-cell (PEMFC) applications [49]. In the initial stage, CA was impregnated with Vulcan XC-72R carbon, and then platinum nanoparticles (from H2PtCl6) were attached to the prepared system by chemical reduction with NaBH4. In turn, Cheng et al. manipulated the potential (potentiostatic deposition or square wave potential deposition) produced Au nanostructures with different sizes and shapes on the surface of carbon fiber paper electrodes [93]. Pt monolayers were deposited onto the resulting urchin-like nanostructures using a surface-limited redox replacement method. The resulting systems were tested in a methanol electrooxidation reaction.
An important step during the synthesis of nanocomposites is the regulation of the surface properties of the MC through different surface-modification methods before the deposition of metal NPs [37][94]. For example, Su et al. deposited uniformly dispersed Pt NPs on the surface of N-doped porous carbon nanospheres (PCNs) [95]. Pt/PCNs hybrids were synthesized by the reduction method using EG as a reducing agent and H2PtCl4 as precursor. The process was assisted by microwave irradiation for 3 min. The authors found that Pt/PCNs exhibited increased activity in the methanol oxidation reaction (MOR) than the commercial E-TEK catalyst. In turn, in Ott’s group, N-functionalized Ketjen Black carbon powder was used as a substrate for Pt nanoparticles [31]. Modification of the carbon support was carried out by pre-oxidizing the pristine carbon in concentrated HNO3 at 70, 200, 400 and 600 ∘C. That modification contributed to the formation of carboxylic, hydroxylic and NOx groups at the surface and also altered the meso- and microporous structure of the carbon supports. An increase in nitrogen content and a higher proportion of mesopores for media subjected to higher temperatures were observed. Following this, the polyol method was used, in which the carbon and Pt precursor (H2PtCl6) were dispersed in ethylene glycol and reduced at 120 ∘C for 2 h. As a result, Pt NPs were deposited on the outer and inner surface of carbon powder particles, and, thus, a high power density in the fuel-cell catalyst, with high stability under voltage cycling, was obtained.
A parameter that also improves fuel-cell performance is the method of catalyst synthesis [96]. Harzer et al. determined the performance of PEMFC cells depending on the way platinum nanoparticles were distributed on Ketjen Black. Using a polyol method and reducing a highly dilute platinum precursor in ethylene glycol, Pt nanoparticles were obtained on the outer carbon surface and in solution. In contrast, using a prewetting method in which the carbon support is impregnated with a highly concentrated Pt precursor solution, nanoparticles were obtained inside the pores of the carbon particles. The catalyst with more Pt particles deposited on the outer surface of the carbon achieved better results.

2.2. Noble-Metal Nanoparticles on Carbon Nanotubes

Discovered by Iijimain in 1991, carbon nanotubes (CNTs) are one of the most widely used substrates for the formation of NMNPs/CMs complexes. They are defined as the ordered, hollow graphene-based nanomaterials made up of carbon sp2 - hybridised atoms. They can be classified into the following two categories: (1) single-walled carbon nanotubes (SWCNTs), consisting of a single sheet of carbon that has been rotated into a tubular form, and (2) multi-walled carbon nanotubes (MWCNTs), which are comprised of several concentric SWCNTs having a mutual longitudinal axis [10][97]. The diameter of CNTs is in the nanometer scale, while their length can reach several microns. Numerous examples of NMNPs/CNTs nanohybrids have been reported in the literature for catalytic applications. The first application of NMNPs/CNTs nanocomposites in heterogeneous catalysis dates back to 1994 [98]. This kind of composite material advantageously integrates the unique properties of individual materials and exhibits some innovative features resulting from the interactions between CNTs and NMNPs. These features directly translate into numerous attractive applications in many fields, especially in catalysis, fuel cells, and environmental-contaminant sensing [10][99][100][101][102].
Obtaining small size, dispersed particles of noble-metal NPs on CNTs is desirable due to high catalytic activity and also for economic reasons. Despite the fact that CNTs exhibit excellent electrical, mechanical, and thermal properties, however, they are chemically inactive and hydrophobic. As a consequence of this, they often do not have enough binding sites for anchoring guest molecules, which results in low dispersion and a large particle size of nanoparticles. Therefore, functionalization of the external surfaces of CNTs is generally carried out [103]. Preformed NMNPs can be deposited on functionalized CNTs or functionalization and synthesis can be carried out in a single process of the formation of NMNPs/CNTs complexes (Figure 2). The surface modification of carbon nanotubes can be performed either covalently or noncovalently [104]. Such CNTs functionalization methods serve both to increase the number of active binding sites for NMNP deposition and to improve the dispersibility of CNTs in solvents, which enhances the catalytic effects [68][69].
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Figure 2. Scheme of the deposition of NMNPs on carbon nanotubes.
Covalent functionalization of CNTs is often carried out via an aggressive oxidation treatment with a HNO3 or HNO3/H2SO4 mixture [104]. This process contributes to the formation of several functional groups, such as carboxylic, carbonyl, and hydroxyl groups, on the surface of nanotubes. It can also be carried out by pretreatment of CNTs in HCl, HF, KMnO4 or H2O2 [105]. Then, covalently functionalized CNTs often undergo subsequent functionalization processes to control the size and dispersion of the NMNPs deposited on them. That approach was used by Wang’s group [106]. In the first step, they functionalized the nanotubes with COOH groups. They then attached amine-terminated ionic liquids (NH2-IL) to the functionalized nanotubes. The gold salt [AuCl4]− was adsorbed to the thus-formed amide bond between MWCNTs-COOH and NH2-IL through electrostatic interaction and ion exchange. As a result of this process, well dispersed 1–2 nm Au NPs were obtained.
Noncovalent functionalization involves the attraction of the hydrophobic end of an adsorbed molecule to the walls of CNTs via van der Waals forces or π–π interactions [27]. This is carried out without disturbing the electron structure of the CNTs, as the covalent bonds are not affected. In this case, the following may be used aromatic organic compounds such as derivatives of pyrene, thionine, or triphenylphosphine, and they contribute to the formation of several functional groups such as thiol, amine, or carboxyl groups, which can be used as the linkers to anchor NMNPs onto CNTs surfaces. In paper [107], it was shown that, by using the in situ polymerization method, it was possible to obtain a homogeneous polymer coating on the surface of MWCNTs, which allows for better dispersion of the nanotubes. An example of such noncovalent functionalization is the modification of carbon nanotubes presented by Zheng [108]. The synthesis of Pd/MWCNTs nanocomposites with particle sizes of 3 nm was achieved by π–π stacking interactions of MWCNTs and naphthalen-1-ylmethylphosphonic acid (NYPA).On such functionalized carbon nanotubes, Pd nanoparticles were deposited by means of a homogeneous precipitation–reduction reaction method by using PdCl2 as a noble metal precursor and NaBH4 as a reduction agent.
Using the same method, it is also possible to form bimetallic-based composites. For example, by reduction with H2PtCl6, the addition of ruthenium and molybdenum precursors (Ru3(CO)12, Mo(CO)6), followed by annealing for 2 h at 400 ∘C in a N2 atmosphere, bilemetallic Pt-Ru/SWCNTs and Pt-Mo/SWCNTs composites were obtained. Moreover, the as-synthesized Pt-Ru/SWCNTs composite showed better current and power densities than Pt/SWCNTs catalysts [109]. Another bimetallic electrocatalyst that plays an important role in the development of direct-methanol-fuel-cell applications is the PtIr/MWCNTs composite [110].
Another way to improve physical and catalytic properties is doping, realized by replacing the carbon atoms in carbon nanotubes with other elements such as nitrogen, phosphorus or boron. For example, Yu et al. [111] reported doping of MWCNTs with phosphorus (P) and nitrogen (N), which improves their durability and increases their electrocatalytic activity. In turn, Jin et al. reported that Pt/CNTs doped with selenium atoms show long-term stability and good activity in comparison with a commercial Pt/C catalyst [112]. Nitrogen can be used both as a dopant and a surfactant in the growth of CNTs [113]. Nitrogen-functionalized CNTs (N-CNTs) have a high number of surface nucleation sites, which allow the anchorage and high dispersion of the noble metal particles [114]. N-CNTs, as substrate material, possess high resistance to surface oxide corrosion, which is an attractive feature, e.g., in oxygen reduction reactions (ORR) [35]. Noteworthy is also paper [115], which shows that boron doping increases the binding energies of transition metals to CNTs supports more than nitrogen. In turn, Rajala and co-workers fabricated platinum nanowires on SWCNTs (Pt NWs/SWCNTs) then pretreated with ozone, which resulted in the formation of polar surface groups on the carbon nanotubes. The fabricated Pt NWs/SWCNTs-O3 composites were more hydrophilic in nature and outperformed in the hydrogen evolution reaction (HER) than non-ozonized compounds [116].
The current trend is the replacement of noble metal nanoparticles in NMNPs/CNTs complexes with cost-effective alternatives, including, for example, nickel. Nickel-doped materials have relatively high electrochemical activity (e.g., ORR, CO2 reduction) and are low-cost [35]. Zhang et al. developed Pd nanoparticles assembled on Ni- and N-doped carbon nanotubes. The resulting CNTs-based composite with homogeneous and monodispersed Pd and Ni particles (2–5 nm and <1 nm, respectively) achieved much better hydrogen evolution reaction (HER) activity compared with the commercial Pd/C sample.
By using an electrochemical method, a very high purity of nanoparticles and their good adhesion to CNTs substrate can be ensured. However, the NMNPs/CNTs nanocomposites prepared by this method usually receive particles with big particles size (between 10 and 100 nm), as shown in He’s work [79]. Pt or bimetallic Pt–Ru nanoparticles were electrodeposited on the CNTs by the potentiostatic method from H2SO4 aqueous solution with ruthenium chloride and chloroplatinic acid. The nanoparticles obtained by this method, although characterized by high purity, also had a grain diameter larger than 60 nm. In order to decrease the size of the metal NPs on the CNTs, Tsai et al. [117] synthesized a Pt and a Pt–Ru/CNTs by potentiostatic electrodeposition in mixed sulfuric acid and ethylene glycol containing aqueous electrolytes. It was found that the addition of EG led to the formation of uniformly dispersed and non-agglomerating Pt and Ru NPs with small sizes, ranging from approximately 4.5–9.5 nm and 4.8–5.2 nm for Pt and Pt–Ru, respectively. Grain size reduction can also be achieved by using methods such as cyclic potential scanning [118], pulsed electrodeposition [119], ultrasonic-electrodeposition [120] and a co-electrodeposition/stripping protocol [121].
The formation of NMNPs/CNTs complexes is also possible by using electroless deposition. An example is the use of the one-pot method, which uses a redox reaction between metal ions and reduced CNTs [122]. Using this procedure, Au and Pd NPs were successfully anchored to the surface of MWCNTs and SWCNTs. Another method that overcomes the limitations of classical electroless deposition is substrate-enhanced electroless deposition (SEED). In the SEED method, CNTs are supported with metal substrates whose redox potential is suitably lower than that of the metal species being reduced. In this case, CNTs are no longer a reducing agent and act only as cathodes and templates for metal deposition from the corresponding noble-metal salts [65].

2.3. Noble-Metal Nanoparticles on Graphene

In addition to carbon nanotubes, graphene (GR) as carbon support also improves the catalytic activity and stability of supported Pt catalysts compared to mesoporous counterparts through enhanced electrical conductivity and metal–substrate interaction [32]. Graphene is a single-atom-thick two-dimensional carbon nanosheet of sp2 bonded carbon atoms packed into a honeycomb lattice that was first synthesized in 2004 by Geim and Novoselov [123]. In 2010, this discovery was awarded the Nobel Prize in Physics for its significant contributions to the development of graphene-based catalysts [124]. Over the years, graphene, as well as its derivatives, including graphene oxide (GO) and reduced graphene oxide (rGO), have become promising candidates for many applications such as batteries, photovoltaic devices, biosensors, supercapacitors and fuel cells. This wide range of applicability is influenced by its unique properties such as large surface area, thermal conductivity, high electron mobility and good stability [10][28][125][126]. Significantly, the numerous oxygen-containing groups present in GO and rGO provide many opportunities for further functionalization and modification [127][128][129][130]. Graphene is an excellent building block in the fabrication of various nanocomposites representing the most recent advance in many fields of chemistry, physics, and electronics [70][125][126][131][132]. Combining GR with noble-metal nanoparticles improves electrochemical performance and provides perfect thermal stability, which is important in electrocatalytic applications (e.g., oxygen reduction and hydrogen/oxygen evolution reactions) [133][134].
The preparation of GR-based noble-metal nanocomposites by using wet-chemical synthesis methods has many advantages, such as an economic cost of production, high yield, mass production and commonness. The most popular strategy is the direct chemical reduction of a noble metal precursor (e.g., HAuCl4, AgNO3, H2PdCl4 or K2PtCl4) in the presence of graphene and its derivative sheets using a reducing agent such as amines, NaBH4, and ascorbic acid [135][136][137]. For example, Iqbal’s group prepared 34 nm mesoporous Pd nanoparticles on rGO sheets modified by the block copolymer F127 [138]. This block copolymer has served as a template for better dispersion of Pd nanoparticles. As a precursor to palladium particles, H2PdCl4 was used, which was reduced by ascorbic acid. By using direct chemical reduction, it is also possible to synthesize GR-based multimetallic noble-metal nanocomposites. For example, Pt-Pd supported on rGO were obtained by the reduction of a noble-metal precursor (H2PtCl6 and PdCl2) by ascorbic acid and octylphenoxypolyethoxyethanol (NP-40) as a soft template [139]. Vilian et al. reported the synthesis of Pt-Au/rGO nanohybrids by a direct chemical-reduction methodology. The reported methanol oxidation is found to exhibit excellent electrocatalytic performance, reliability, and stability, surpassing that of several reported modified electrodes that can also be used for platinum-based catalysts in fuel-cell applications [140].
The chemical reduction process can also be assisted by microwave irradiation for the synthesis of chemically converted graphene sheets and metal nanoparticles dispersed on them [141]. In turn, the sonochemical method has been used, for example, in the development of Au/GR nanocomposite [142]. In this research, by using an ultrasonication probe of 20 kHz on the surface of exfoliated few-layer graphene sheets, the in situ growth of gold nanoparticles (Au NPs) after the reduction of gold chloride took place. Alternatively, Huang et al. synthesized Pd/rGO nanohybrids with ~3 nm nanoparticles using a one-pot photoassisted citrate reduction. In the process shown, the mixture of GO solution, Na2PdCl4, sodium citrate, and deionized water was irradiated by a 500 W high-pressure mercury lamp for 12 h. This synthetic approach allows for the formation onto the rGO surface of Pd nanoparticles with the desired size with excellent activity and stability of complexes in oxygen reduction and ethanol oxidation reactions. The prepared Pd/rGO nanocomposite exhibited 5.2 times higher mass activity for ethanol oxidation reaction than the commercial Pt/C catalyst [143].
By analogy with other carbonaceous supports, it is possible to use an electroless method to prepare NMNPs/GR composites. In this case, graphene derivatives (GO or rGO) themselves can donate electrons to reduce the noble-metal precursors in an aqueous phase without any additional reductant. In accordance with this, metal precursors (e.g., HAuCl4, H2PdCl4, or AgNO3) can be reduced to form metallic Au, Pd, and Ag nanoparticles, respectively, solely by GO or rGO [135][144][145]. An example would be the work of [146], in the synthesis of the redox reaction between Au, Ag or Pd precursors and the partially reduced graphene oxide (prGO) in an aqueous solution. The as-obtained Au, Ag and Pd/prGO nanocomposites display excellent catalytic activities, and the size distributions of the Au, Ag, and Pd particles were 1–20 nm, 3–10 nm and 0.5–3 nm, respectively.
Interesting conclusions presented by Qin et al. claim that a heating treatment and strong alkaline conditions enhance the reducing ability of the hydroxyl groups on GO. In their work, Au/rGO nanocomposites were prepared through a one-pot strategy, conducted by heating a mixture of HAuCl4, NaOH and graphene oxide solution at 90 ∘C [145]. It is also possible to obtain NMNPs/GR nanocomposites by using pure graphene without any additional groups. This strategy was proposed in a paper by Jeong et al., in which graphene was covered onto a reducing substrate (e.g., Si or Al) [137]. As a result, Au/GR or Pt/GR nanocomposites could be prepared because electrons were transferred from the substrate, via graphene, to the precursors (HAuCl4 or KPtCl4). In Zou et al.’s paper, using a two-step electrochemical deposition method, spherical Au nanoparticles and a 3D flower-like structure graphene were obtained on a glassy carbon electrode (Au/rGE/GCE) [147]. Another example was presented by Liu et al.: an electrochemically seed-mediated method by which sub-10 nm tetrahexahedral (THH) Pt NCs supported on graphene were synthesized. The obtained nanohybrids exhibited a higher mass activity than a commercial Pt/C catalyst for ethanol electrooxidation [148].
All of the GR-based nanohybrid examples presented above focus on graphene and its derivatives’ 2D morphology. However, the practical application of graphene is associated with difficulties in the form of the stacking and folding of its sheets. In particular, it is hindered by 2D GR wrinkles that wrap around MNNPs. This limits electron and mass transport and makes its application in electrocatalysis much more difficult [149]. Therefore, the focus has been on designing various 3D GR nanostructures (e.g., framework, network, foam, etc.). These treatments aim to minimize wrinkles as well as reduce agglomeration of nanoparticles [150][151][152][153]. Qiu et al., by using a layer-by-layer assembly method, presented a versatile synthesis strategy based on sacrificial templates to obtain three-dimensional graphene-assisted PtM (M = Fe, Co, Ni) nanospheres [154]. In the first step, electrostatic attraction was used to wind 2D GO sheets on positively charged SiO2 nanospheres. Next, PtM (M = Fe, Co, Ni) alloy nanoparticles were deposited on the surface of 3D rGO nanospheres. Finally, after etching SiO2, the 3D rGO-supported PtM hollow nanospheres were formed. These nanocomposites exhibit enhanced electrocatalytic activity, durability, and stability for methanol oxidation reactions (MOR), compared with commercial Pt/C. On the other hand, Yao et al. showed that Pd nanoparticles encapsulated in hollow microspheres of N-doped graphene, exhibited higher EOR activity in an alkaline medium than Pd/rGO [155]. Additionally, it should be noted that the structure of N-doped GR hollow microspheres greatly facilitates the diffusion of reactants, which, in turn, improves the catalytic reactions [156].
Reducing the particle size of noble metals positively affects the activity of the catalysts constructed on their basis, by significantly increasing the specific activity per metal atom. Therefore, single-atom catalysts (SACs) containing single-metal atoms anchored on supports are sought. The surface of pristine graphene and metal atoms are not firmly fixed, and they easily diffuse together to form nanoparticles [157]. Therefore, obtaining dispersed metal atoms on pure GR is difficult. Accordingly, the surfaces of an ultrathin thickness and large specific surface area of 2D GR nanosheets have been doped with heteroatoms such as N, O, or S, which provide anchors for SAC (Figure 3) [158].
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Figure 3. Scheme of doped graphene nanosheets with single-atom catalysts.
The atomic layer deposition (ALD) technique has become a promising method to obtain monoatomic catalysts on graphene derivatives [157][159][160]. This cyclic process was based on sequential self-terminating reactions between a solid surface and gas-phase precursor molecules [161]. For example, Sun et al. described the practical construction of isolated Pt atoms anchored in graphene nanosheets (GNSs) using the ALD method [162]. In the construction process, oxygen and (methylcyclopentadienyl)-trimethyl platinum (MeCpPtMe3) were used as precursors. In the first step, the number of oxygen-functional groups on the rGO surface was selected to form a thin Pt monolayer. Subsequently, oxygen exposure formed new surface oxygen on the pre-existing Pt layer. This process completed one cycle of a complete reaction. The morphology, size and loading density of platinum over graphene were controlled by simply tuning the cycles of the ALD (i.e., 50, 100, and 150 cycles). Finally, the best results, i.e., single Pt atoms, were obtained after 50 ALD cycles. All the discussed ALDPt/GNSs catalysts show several-times-higher activity for MOR than the Pt/C catalyst. Among them, ALD50Pt/GNS is more than 9.5 times more active than the Pt/C catalyst. Another example of using the ALD method was presented by Yan et al. They described the growth of single Pd atoms anchored to phenyl groups on rGO substrates [160]. Using the same method, they also presented the deposition of Pt2 dimers on graphene [163].
Wet impregnation is another method for the synthesis of single noble-metal atoms supported on graphene [164][165][166]. For example, Zhang et al. synthesized single Ru atoms on N-doped GD [165]. For example, Zhang et al. synthesized single Ru atoms on N-doped GO by using the Ru(NH3)6Cl3 as a precursor. The mixture thus formed was lyophilized to prevent the restacking of GO sheets. The resulting GO impregnated with Ru atoms was annealed in NH3 gas at 750 ∘C. This process led to the reduction of GO to form GR. Finally, nitrogen atoms were doped into the graphene plane as anchor sites for ruthenium atoms.

This entry is adapted from the peer-reviewed paper 10.3390/cryst12050584

References

  1. Richter, F.; Meng, Y.; Klasen, T.; Sahraoui, L.; Schüth, F. Structural mimicking of inorganic catalyst supports with polydivinylbenzene to improve performance in the selective aerobic oxidation of ethanol and glycerol in water. J. Catal. 2013, 308, 341–351.
  2. Martinuzzi, S.; Cozzula, D.; Centomo, P.; Zecca, M.; Müller, T.E. The distinct role of the flexible polymer matrix in catalytic conversions over immobilised nanoparticles. RSC Adv. 2015, 5, 56181–56188.
  3. Koga, H.; Tokunaga, E.; Hidaka, M.; Umemura, Y.; Saito, T.; Isogai, A.; Kitaoka, T. Topochemical synthesis and catalysis of metal nanoparticles exposed on crystalline cellulose nanofibers. Chem. Commun. 2010, 46, 8567–8569.
  4. Turner, M.; Golovko, V.; Vaughan, O.; Abdulkin, P.; Berenguer-Murcia, A.; Tikhov, M.; Johnson, B.; Lambert, R. Selective oxidation with dioxygen by gold nanoparticle catalysts derived from 55-atom clusters. Nature 2008, 454, 981–983.
  5. Yamada, Y.; Tsung, C.K.; Huang, W.; Huo, Z.; Habas, S.; Soejima, T.; Aliaga, C.; Somorjai, G.; Yang, P. Nanocrystal bilayer for tandem catalysis. Nat. Chem. 2011, 3, 372–376.
  6. An, K.; Alayoglu, S.; Musselwhite, N.; Na, K.; Somorjai, G.A. Designed Catalysts from Pt Nanoparticles Supported on Macroporous Oxides for Selective Isomerization of n-Hexane. J. Am. Chem. Soc. 2014, 136, 6830–6833.
  7. Kuo, C.H.; Tang, Y.; Chou, L.Y.; Sneed, B.T.; Brodsky, C.N.; Zhao, Z.; Tsung, C.K. Yolk–Shell Nanocrystal@ZIF-8 Nanostructures for Gas-Phase Heterogeneous Catalysis with Selectivity Control. J. Am. Chem. Soc. 2012, 134, 14345–14348.
  8. Joo, S.H.; Park, J.; Tsung, C.K.; Yamada, Y.; Yang, P.; Somorjai, G. Thermally Stable Pt/Mesoporous Silica Core-shell Nanocatalysts for High-Temperature Reactions. Nat. Mater. 2008, 8, 126–131.
  9. Wang, S.; Wang, J.; Zhao, Q.; Li, D.; Wang, J.Q.; Cho, M.; Cho, H.; Terasaki, O.; Chen, S.; Wan, Y. Highly Active Heterogeneous 3 nm Gold Nanoparticles on Mesoporous Carbon as Catalysts for Low-Temperature Selective Oxidation and Reduction in Water. ACS Catal. 2015, 5, 797–802.
  10. Lam, E.; Luong, J.H. Carbon Materials as Catalyst Supports and Catalysts in the Transformation of Biomass to Fuels and Chemicals. ACS Catal. 2014, 4, 3393–3410.
  11. Zhou, R.; Qiao, S. Silver/Nitrogen-Doped Graphene Interaction and Its Effect on Electrocatalytic Oxygen Reduction. Chem. Mater. 2014, 26, 5868–5873.
  12. Zheng, Y.; Luo, R.; Xu, Y.; Zhang, L.; Liu, P.; Chen, Q. Adsorbate-Mediated Deposition of Noble-Metal Nanoparticles on Carbon Substrates for Electrocatalysis. ACS Appl. Energy Mater. 2020, 3, 6460–6465.
  13. Frackowiak, E.; Beguin, F. Carbon materials for the electrochemical storage of energy in capacitors. Carbon 2001, 39, 937–950.
  14. Yang, T.; Ling, H.; Lamonier, J.F.; Jaroniec, M.; Huang, J.; Monteiro, M.J.; Liu, J. A synthetic strategy for carbon nanospheres impregnated with highly monodispersed metal nanoparticles. NPG Asia Mater. 2016, 8, e240.
  15. Dai, L.; Chang, D.W.; Baek, J.B.; Lu, W. Carbon nanomaterials: Carbon nanomaterials for advanced energy conversion and storage (small 8/2012). Small 2012, 8, 1122.
  16. Noor, T.; Yaqoob, L.; Iqbal, N. Recent Advances in Electrocatalysis of Oxygen Evolution Reaction using Noble-Metal, Transition-Metal, and Carbon-Based Materials. ChemElectroChem 2021, 8, 447–483.
  17. Dai, L.; Xue, Y.; Qu, L.; Choi, H.J.; Baek, J.B. Metal-free catalysts for oxygen reduction reaction. Chem. Rev. 2015, 115, 4823–4892.
  18. Liu, H.; Song, C.; Zhang, L.; Zhang, J.; Wang, H.; Wilkinson, D.P. A review of anode catalysis in the direct methanol fuel cell. J. Power Sources 2006, 155, 95–110.
  19. Uchida, M.; Aoyama, Y.; Tanabe, M.; Yanagihara, N.; Eda, N.; Ohta, A. Influences of both carbon supports and heat-treatment of supported catalyst on electrochemical oxidation of methanol. J. Electrochem. Soc. 1995, 142, 2572.
  20. Liu, Y.; Ji, C.; Gu, W.; Jorne, J.; Gasteiger, H.A. Effects of catalyst carbon support on proton conduction and cathode performance in PEM fuel cells. J. Electrochem. Soc. 2011, 158, B614.
  21. Qu, W.L.; Wang, Z.B.; Jiang, Z.Z.; Gu, D.M.; Yin, G.P. Investigation on performance of Pd/Al2O3-C catalyst synthesized by microwave assisted polyol process for electrooxidation of formic acid. Rsc Adv. 2012, 2, 344–350.
  22. Moore, A.D.; Holmes, S.M.; Roberts, E.P. Evaluation of porous carbon substrates as catalyst supports for the cathode of direct methanol fuel cells. RSC Adv. 2012, 2, 1669–1674.
  23. Vogel, W. Size contraction in Pt/C and PtRu/C commercial E-TEK electrocatalysts: An in situ X-ray diffraction study. J. Phys. Chem. C 2008, 112, 13475–13482.
  24. Chen, T.W.; Kalimuthu, P.; Veerakumar, P.; Lin, K.C.; Chen, S.M.; Ramachandran, R.; Mariyappan, V.; Chitra, S. Recent Developments in Carbon-Based Nanocomposites for Fuel Cell Applications: A Review. Molecules 2022, 27, 761.
  25. Li, J.; Stephanopoulos, M.F.; Xia, Y. Introduction: Heterogeneous single-atom catalysis. Chem. Rev. 2020, 120, 11699–11702.
  26. Wang, A.; Li, J.; Zhang, T. Heterogeneous single-atom catalysis. Nat. Rev. Chem. 2018, 2, 65–81.
  27. Wu, B.; Kuang, Y.; Zhang, X.; Chen, J. Noble metal nanoparticles/carbon nanotubes nanohybrids: Synthesis and applications. Nano Today 2011, 6, 75–90.
  28. Khalil, I.; Julkapli, N.M.; Yehye, W.A.; Basirun, W.J.; Bhargava, S.K. Graphene–gold nanoparticles hybrid—Synthesis, functionalization, and application in a electrochemical and surface-enhanced raman scattering biosensor. Materials 2016, 9, 406.
  29. Chung, S.; Ham, K.; Kang, S.; Ju, H.; Lee, J. Enhanced corrosion tolerance and highly durable ORR activity by low Pt electrocatalyst on unique pore structured CNF in PEM fuel cell. Electrochim. Acta 2020, 348, 136346.
  30. Jeon, Y.; Ji, Y.; Cho, Y.I.; Lee, C.; Park, D.H.; Shul, Y.G. Oxide–Carbon Nanofibrous Composite Support for a Highly Active and Stable Polymer Electrolyte Membrane Fuel-Cell Catalyst. ACS Nano 2018, 12, 6819–6829.
  31. Ott, S.; Orfanidi, A.; Schmies, H.; Anke, B.; Nong, H.N.; Hübner, J.; Gernert, U.; Gliech, M.; Lerch, M.; Strasser, P. Ionomer distribution control in porous carbon-supported catalyst layers for high-power and low Pt-loaded proton exchange membrane fuel cells. Nat. Mater. 2020, 19, 77–85.
  32. Mardle, P.; Ji, X.; Wu, J.; Guan, S.; Dong, H.; Du, S. Thin film electrodes from Pt nanorods supported on aligned N-CNTs for proton exchange membrane fuel cells. Appl. Catal. B Environ. 2020, 260, 118031.
  33. Orfanidi, A.; Madkikar, P.; El-Sayed, H.A.; Harzer, G.S.; Kratky, T.; Gasteiger, H.A. The Key to High Performance Low Pt Loaded Electrodes. J. Electrochem. Soc. 2017, 164, F418–F426.
  34. Du, S.; Lu, Y.; Steinberger-Wilckens, R. PtPd nanowire arrays supported on reduced graphene oxide as advanced electrocatalysts for methanol oxidation. Carbon 2014, 79, 346–353.
  35. Zhang, X.; Yang, P.; Jiang, S.P. Pd nanoparticles assembled on Ni- and N-doped carbon nanotubes towards superior electrochemical activity. Int. J. Hydrog. Energy 2021, 46, 2065–2074.
  36. Tetrahydrofuran-functionalized multi-walled carbon nanotubes as effective support for Pt and PtSn electrocatalysts of fuel cells. Electrochim. Acta 2010, 55, 2964–2971.
  37. Alegre, C.; Gálvez, M.E.; Baquedano, E.; Moliner, R.; Pastor, E.; Lázaro, M.J. Oxygen-Functionalized Highly Mesoporous Carbon Xerogel Based Catalysts for Direct Methanol Fuel Cell Anodes. J. Phys. Chem. C 2013, 117, 13045–13058.
  38. La-Torre-Riveros, L.; Guzman-Blas, R.; Méndez-Torres, A.E.; Prelas, M.; Tryk, D.A.; Cabrera, C.R. Diamond Nanoparticles as a Support for Pt and PtRu Catalysts for Direct Methanol Fuel Cells. ACS Appl. Mater. Interfaces 2012, 4, 1134–1147.
  39. Beltrán-Gastélum, M.; Salazar-Gastélum, M.; Flores-Hernández, J.; Botte, G.; Pérez-Sicairos, S.; Romero-Castañon, T.; Reynoso-Soto, E.; Félix-Navarro, R. Pt-Au nanoparticles on graphene for oxygen reduction reaction: Stability and performance on proton exchange membrane fuel cell. Energy 2019, 181, 1225–1234.
  40. Şanlı, L.I.; Yarar, B.; Bayram, V.; Gürsel, S.A. Electrosprayed catalyst layers based on graphene–carbon black hybrids for the next-generation fuel cell electrodes. J. Mater. Sci. 2017, 52, 2091–2102.
  41. Zhou, Y.; Hu, X.; Guo, S.; Yu, C.; Zhong, S.; Liu, X. Multi-functional graphene/carbon nanotube aerogels for its applications in supercapacitor and direct methanol fuel cell. Electrochim. Acta 2018, 264, 12–19.
  42. Chen, D.J.; Zhang, Q.; Feng, J.X.; Ju, K.J.; Wang, A.J.; Wei, J.; Feng, J.J. One-pot wet-chemical co-reduction synthesis of bimetallic gold–platinum nanochains supported on reduced graphene oxide with enhanced electrocatalytic activity. J. Power Sources 2015, 287, 363–369.
  43. Pan, D.; Li, X.; Zhang, A. Platinum assisted by carbon quantum dots for methanol electro-oxidation. Appl. Surf. Sci. 2018, 427, 715–723.
  44. Deming, C.P.; Mercado, R.; Lu, J.E.; Gadiraju, V.; Khan, M.; Chen, S. Oxygen Electroreduction Catalyzed by Palladium Nanoparticles Supported on Nitrogen-Doped Graphene Quantum Dots: Impacts of Nitrogen Dopants. ACS Sustain. Chem. Eng. 2016, 4, 6580–6589.
  45. Zhang, M.; Li, H.; Chen, J.; Yi, L.; Shao, P.; Xu, C.Y.; Wen, Z. Nitrogen-doped graphite encapsulating RuCo nanoparticles toward high-activity catalysis of water oxidation and reduction. Chem. Eng. J. 2021, 422, 130077.
  46. Mondal, S.K. Synthesis of Mesoporous Fullerene and its Platinum Composite: A Catalyst for PEMFc. J. Electrochem. Soc. 2012, 159, K156–K160.
  47. McPherson, I.J.; Ash, P.A.; Jones, L.; Varambhia, A.; Jacobs, R.M.J.; Vincent, K.A. Electrochemical CO Oxidation at Platinum on Carbon Studied through Analysis of Anomalous in Situ IR Spectra. J. Phys. Chem. C 2017, 121, 17176–17187.
  48. Zhang, X.; Zhang, J.W.; Xiang, P.H.; Qiao, J. Fabrication of graphene-fullerene hybrid by self-assembly and its application as support material for methanol electrocatalytic oxidation reaction. Appl. Surf. Sci. 2018, 440, 477–483.
  49. Gu, K.; Kim, E.; Sharma, S.; Sharma, P.; Bliznakov, S.; Hsiao, B.; Rafailovich, M. Mesoporous carbon aerogel with tunable porosity as the catalyst support for enhanced proton-exchange membrane fuel cell performance. Mater. Today Energy 2021, 19, 100560.
  50. Kin, Y.; Saito, K.; Oda, H.; Ando, T.; Nakagawa, K. Development of Direct Methanol Fuel Cell Catalyst Using Marimo Nano Carbon. Catal. Lett. 2019, 149, 1–6.
  51. Bak, J.; Kim, H.; Lee, S.; Kim, M.; Kim, E.J.; Roh, J.; Shin, J.; Choi, C.H.; Cho, E. Boosting the Role of Ir in Mitigating Corrosion of Carbon Support by Alloying with Pt. ACS Catal. 2020, 10, 12300–12309.
  52. Luo, F.; Hu, H.; Zhao, X.; Yang, Z.; Zhang, Q.; Xu, J.; Kaneko, T.; Yoshida, Y.; Zhu, C.; Cai, W. Robust and Stable Acidic Overall Water Splitting on Ir Single Atoms. Nano Lett. 2020, 20, 2120–2128.
  53. Choudhary, A.K.; Pramanik, H. Addition of rhenium (Re) to Pt-Ru/f-MWCNT anode electrocatalysts for enhancement of ethanol electrooxidation in half cell and single direct ethanol fuel cell. Int. J. Hydrog. Energy 2020, 45, 13300–13321.
  54. Tsai, M.C.; Yeh, T.K.; Tsai, C.H. Electrodeposition of platinum-ruthenium nanoparticles on carbon nanotubes directly grown on carbon cloths for methanol oxidation. Mater. Chem. Phys. 2008, 109, 422–428.
  55. Zhou, Y.G.; Chen, J.J.; Wang, F.b.; Sheng, Z.H.; Xia, X.H. A facile approach to the synthesis of highly electroactive Pt nanoparticles on graphene as an anode catalyst for direct methanol fuel cells. Chem. Commun. 2010, 46, 5951–5953.
  56. Yao, Z.; Zhu, M.; Jiang, F.; Du, Y.; Wang, C.; Yang, P. Highly efficient electrocatalytic performance based on Pt nanoflowers modified reduced graphene oxide/carbon cloth electrode. J. Mater. Chem. 2012, 22, 13707–13713.
  57. Ahn, S.H.; Choi, I.; Kwon, O.J.; Kim, J. One-step co-electrodeposition of Pt-Ru electrocatalysts on carbon paper for direct methanol fuel. Chem. Eng. J. 2012, 181, 276–280.
  58. Gao, L.; Ding, L.; Fan, L. Pt nanoflower/graphene-layered composites by ZnO nanoparticle expansion of graphite and their enhanced electrocatalytic activity for methanol oxidation. Electrochim. Acta 2013, 106, 159–164.
  59. Gao, F.; Yang, N.; Smirnov, W.; Obloh, H.; Nebel, C. Size-controllable and homogeneous platinum nanoparticles on diamond using wet chemically assisted electrodeposition. Electrochim. Acta 2013, 90, 445–451.
  60. Mavrokefalos, C.; Hasan, M.; Rohan, J.; Foord, J. Enhanced Mass Activity and Stability of Bimetallic Pd-Ni Nanoparticles on Boron-Doped Diamond for Direct Ethanol Fuel Cell Applications. ChemElectroChem 2017, 5, 455–463.
  61. Dhanasekaran, P.; Lokesh, K.; Ojha, P.; Sahu, A.; Bhat, S.; Kalpana, D. Electrochemical deposition of three-dimensional platinum nanoflowers for high-performance polymer electrolyte fuel cells. J. Colloid Interface Sci. 2020, 572, 198–206.
  62. Goh, Y.A.; Chen, X.; Yasin, F.M.; Eggers, P.K.; Boulos, R.A.; Wang, X.; Chua, H.T.; Raston, C.L. Shear flow assisted decoration of carbon nano-onions with platinum nanoparticles. Chem. Commun. 2013, 49, 5171–5173.
  63. Wang, Q.; Geng, B.; Tao, B. A facile room temperature chemical route to Pt nanocube/carbon nanotube heterostructures with enhanced electrocatalysis. J. Power Sources 2011, 196, 191–195.
  64. Chen, X.; Hou, Y.; Wang, H.; Cao, Y.; He, J. Facile Deposition of Pd Nanoparticles on Carbon Nanotube Microparticles and Their Catalytic Activity for Suzuki Coupling Reactions. J. Phys. Chem. C 2008, 112, 8172–8176.
  65. Qu, L.; Dai, L. Substrate-Enhanced Electroless Deposition of Metal Nanoparticles on Carbon Nanotubes. J. Am. Chem. Soc. 2005, 127, 10806–10807.
  66. Ming, M.; Zhang, Y.; He, C.; Zhao, L.; Niu, S.; Fan, G.; Hu, J.S. Room-Temperature Sustainable Synthesis of Selected Platinum Group Metal (PGM = Ir, Rh, and Ru) Nanocatalysts Well-Dispersed on Porous Carbon for Efficient Hydrogen Evolution and Oxidation. Small 2019, 15, 1903057.
  67. Bian, Y.; Wang, H.; Gao, Z.; Hu, J.; Liu, D.; Dai, L. A facile approach to high-performance trifunctional electrocatalysts by substrate-enhanced electroless deposition of Pt/NiO/Ni on carbon nanotubes. Nanoscale 2020, 12, 14615–14625.
  68. Bahr, J.L.; Tour, J.M. Covalent chemistry of single-wall carbon nanotubes. J. Mater. Chem. 2002, 12, 1952–1958.
  69. Jiang, L.; Gao, L. Modified carbon nanotubes: An effective way to selective attachment of gold nanoparticles. Carbon 2003, 41, 2923–2929.
  70. Georgakilas, V.; Perman, J.A.; Tucek, J.; Zboril, R. Broad family of carbon nanoallotropes: Classification, chemistry, and applications of fullerenes, carbon dots, nanotubes, graphene, nanodiamonds, and combined superstructures. Chem. Rev. 2015, 115, 4744–4822.
  71. Labulo, A.H.; Martincigh, B.S.; Omondi, B.; Nyamori, V.O. Advances in carbon nanotubes as efficacious supports for palladium-catalysed carbon–carbon cross-coupling reactions. J. Mater. Sci. 2017, 52, 9225–9248.
  72. Zhang, R.Y.; Olin, H. Gold-carbon nanotube nanocomposites: Synthesis and applications. Int. J. Biomed. Nanosci. Nanotechnol. 2011, 2, 112–135.
  73. Huang, H.; Wang, X. Recent progress on carbon-based support materials for electrocatalysts of direct methanol fuel cells. J. Mater. Chem. A 2014, 2, 6266–6291.
  74. Li, H.; Chang, G.; Zhang, Y.; Tian, J.; Liu, S.; Luo, Y.; Asiri, A.M.; Al-Youbi, A.O.; Sun, X. Photocatalytic synthesis of highly dispersed Pd nanoparticles on reduced graphene oxide and their application in methanol electro-oxidation. Catal. Sci. Technol. 2012, 2, 1153–1156.
  75. Fan, J.J.; Fan, Y.J.; Wang, R.X.; Xiang, S.; Tang, H.G.; Sun, S.G. A novel strategy for the synthesis of sulfur-doped carbon nanotubes as a highly efficient Pt catalyst support toward the methanol oxidation reaction. J. Mater. Chem. A 2017, 5, 19467–19475.
  76. Lu, R.; Zang, J.; Wang, Y.; Zhao, Y. Microwave synthesis and properties of nanodiamond supported PtRu electrocatalyst for methanol oxidation. Electrochim. Acta 2012, 60, 329–333.
  77. Hsieh, C.T.; Hung, W.M.; Chen, W.Y.; Lin, J.Y. Microwave-assisted polyol synthesis of Pt–Zn electrocatalysts on carbon nanotube electrodes for methanol oxidation. Int. J. Hydrog. Energy 2011, 36, 2765–2772.
  78. Hsieh, C.T.; Wei, J.M.; Hsiao, H.T.; Chen, W.Y. Fabrication of flower-like platinum clusters onto graphene sheets by pulse electrochemical deposition. Electrochim. Acta 2012, 64, 177–182.
  79. He, Z.; Chen, J.; Liu, D.; Zhou, H.; Kuang, Y. Electrodeposition of Pt-Ru nanoparticles on carbon nanotubes and their electrocatalytic properties for methanol electrooxidation. Diam. Relat. Mater. 2004, 13, 1764–1770.
  80. Choi, H.C.; Shim, M.; Bangsaruntip, S.; Dai, H. Spontaneous Reduction of Metal Ions on the Sidewalls of Carbon Nanotubes. J. Am. Chem. Soc. 2002, 124, 9058–9059.
  81. Shen, X.; Xia, X.; Du, Y.; Wang, C. Electroless deposition of Au nanoparticles on reduced graphene oxide/polyimide film for electrochemical detection of hydroquinone and catechol. Front. Mater. Sci. 2017, 11, 262–270.
  82. Liu, X.W.; Mao, J.J.; Liu, P.D.; Wei, X.W. Fabrication of metal-graphene hybrid materials by electroless deposition. Carbon 2011, 49, 477–483.
  83. Qi, J.; Jiang, L.; Tang, Q.; Zhu, S.; Wang, S.; Yi, B.; Sun, G. Synthesis of graphitic mesoporous carbons with different surface areas and their use in direct methanol fuel cells. Carbon 2012, 50, 2824–2831.
  84. Calvillo, L.; Celorrio, V.; Moliner, R.; Garcia, A.; Caméan, I.; Lazaro, M. Comparative study of Pt catalysts supported on different high conductive carbon materials for methanol and ethanol oxidation. Electrochim. Acta 2013, 102, 19–27.
  85. Cao, J.; Chen, Z.; Xu, J.; Wang, W.; Chen, Z. Mesoporous carbon synthesized from dual colloidal silica/block copolymer template approach as the support of platinum nanoparticles for direct methanol fuel cells. Electrochim. Acta 2013, 88, 184–192.
  86. Yarlagadda, V.; Carpenter, M.K.; Moylan, T.E.; Kukreja, R.S.; Koestner, R.; Gu, W.; Thompson, L.; Kongkanand, A. Boosting fuel cell performance with accessible carbon mesopores. ACS Energy Lett. 2018, 3, 618–621.
  87. Maiyalagan, T.; Alaje, T.O.; Scott, K. Highly stable Pt–Ru nanoparticles supported on three-dimensional cubic ordered mesoporous carbon (Pt–Ru/CMK-8) as promising electrocatalysts for methanol oxidation. J. Phys. Chem. C 2012, 116, 2630–2638.
  88. Su, F.; Poh, C.K.; Tian, Z.; Xu, G.; Koh, G.; Wang, Z.; Liu, Z.; Lin, J. Electrochemical behavior of Pt nanoparticles supported on meso-and microporous carbons for fuel cells. Energy Fuels 2010, 24, 3727–3732.
  89. Yu, M.; Han, Y.; Li, J.; Wang, L. One-step synthesis of sodium carboxymethyl cellulose-derived carbon aerogel/nickel oxide composites for energy storage. Chem. Eng. J. 2017, 324, 287–295.
  90. Han, S.; Sun, Q.; Zheng, H.; Li, J.; Jin, C. Green and facile fabrication of carbon aerogels from cellulose-based waste newspaper for solving organic pollution. Carbohydr. Polym. 2016, 136, 95–100.
  91. Chen, Y.; Zhang, L.; Yang, Y.; Pang, B.; Xu, W.; Duan, G.; Jiang, S.; Zhang, K. Recent progress on nanocellulose aerogels: Preparation, modification, composite fabrication, applications. Adv. Mater. 2021, 33, 2005569.
  92. Antolini, E. Lignocellulose, cellulose and lignin as renewable alternative fuels for direct biomass fuel cells. ChemSusChem 2021, 14, 189–207.
  93. Cheng, S.; Rettew, R.E.; Sauerbrey, M.; Alamgir, F.M. Architecture-dependent surface chemistry for Pt monolayers on carbon-supported Au. ACS Appl. Mater. Interfaces 2011, 3, 3948–3956.
  94. Park, S.J.; Kim, B.J.; Lee, S.Y. Effect of surface modification of mesoporous carbon supports on the electrochemical activity of fuel cells. J. Colloid Interface Sci. 2013, 405, 150–156.
  95. Su, F.; Tian, Z.; Poh, C.K.; Wang, Z.; Lim, S.H.; Liu, Z.; Lin, J. Pt nanoparticles supported on nitrogen-doped porous carbon nanospheres as an electrocatalyst for fuel cells. Chem. Mater. 2010, 22, 832–839.
  96. Harzer, G.S.; Orfanidi, A.; El-Sayed, H.; Madkikar, P.; Gasteiger, H.A. Tailoring catalyst morphology towards high performance for low Pt loaded PEMFC cathodes. J. Electrochem. Soc. 2018, 165, F770.
  97. Saifuddin, N.; Raziah, A.; Junizah, A. Carbon Nanotubes: A Review on Structure and Their Interaction with Proteins. J. Chem. 2013, 2013, 676815.
  98. Planeix, J.; Coustel, N.; Coq, B.; Brotons, V.; Kumbhar, P.; Dutartre, R.; Geneste, P.; Bernier, P.; Ajayan, P. Application of carbon nanotubes as supports in heterogeneous catalysis. J. Am. Chem. Soc. 1994, 116, 7935–7936.
  99. Brandao, A.T.; Rosoiu, S.; Costa, R.; Lazar, O.A.; Silva, A.F.; Anicai, L.; Pereira, C.M.; Enachescu, M. Characterization and electrochemical studies of MWCNTs decorated with Ag nanoparticles through pulse reversed current electrodeposition using a deep eutectic solvent for energy storage applications. J. Mater. Res. Technol. 2021, 15, 342–359.
  100. Ohtaka, A.; Sansano, J.M.; Nájera, C.; Miguel-García, I.; Berenguer-Murcia, Á.; Cazorla-Amorós, D. Palladium and Bimetallic Palladium–Nickel Nanoparticles Supported on Multiwalled Carbon Nanotubes: Application to Carbon-Carbon Bond-Forming Reactions in Water. ChemCatChem 2015, 7, 1841–1847.
  101. Li, Y.; Fu, Y.; Lai, C.; Qin, L.; Li, B.; Liu, S.; Yi, H.; Xu, F.; Li, L.; Zhang, M.; et al. Porous materials confining noble metals for the catalytic reduction of nitroaromatics: Controllable synthesis and enhanced mechanism. Environ. Sci.-Nano 2021, 8, 3067–3097.
  102. Guo, D.J.; Cui, S.K. A composite strategy to prepare high active Pt-WO3/MWCNT catalysts for methanol electro-oxidation. J. Phys. Chem. Solids 2021, 159, 110293.
  103. Lee, K.M.; Li, L.; Dai, L. Asymmetric end-functionalization of multi-walled carbon nanotubes. J. Am. Chem. Soc. 2005, 127, 4122–4123.
  104. De Volder, M.F.; Tawfick, S.H.; Baughman, R.H.; Hart, A.J. Carbon nanotubes: Present and future commercial applications. Science 2013, 339, 535–539.
  105. Li, Y.; Hu, F.P.; Wang, X.; Shen, P.K. Anchoring metal nanoparticles on hydrofluoric acid treated multiwalled carbon nanotubes as stable electrocatalysts. Electrochem. Commun. 2008, 10, 1101–1104.
  106. Wang, Z.; Zhang, Q.; Kuehner, D.; Ivaska, A.; Niu, L. Green synthesis of 1–2 nm gold nanoparticles stabilized by amine-terminated ionic liquid and their electrocatalytic activity in oxygen reduction. Green Chem. 2008, 10, 907–909.
  107. Tunckol, M.; Fantini, S.; Malbosc, F.; Durand, J.; Serp, P. Effect of the synthetic strategy on the non-covalent functionalization of multi-walled carbon nanotubes with polymerized ionic liquids. Carbon 2013, 57, 209–216.
  108. Zheng, M.; Li, P.; Fu, G.; Chen, Y.; Zhou, Y.; Tang, Y.; Lu, T. Efficient anchorage of highly dispersed and ultrafine palladium nanoparticles on the water-soluble phosphonate functionalized multiwall carbon nanotubes. Appl. Catal. B Environ. 2013, 129, 394–402.
  109. Maya-Cornejo, J.; Garcia-Bernabé, A.; Compañ, V. Bimetallic Pt-M electrocatalysts supported on single-wall carbon nanotubes for hydrogen and methanol electrooxidation in fuel cells applications. Int. J. Hydrog. Energy 2018, 43, 872–884.
  110. Bhuvanendran, N.; Ravichandran, S.; Zhang, W.; Ma, Q.; Xu, Q.; Khotseng, L.; Su, H. Highly efficient methanol oxidation on durable PtxIr/MWCNT catalysts for direct methanol fuel cell applications. Int. J. Hydrog. Energy 2020, 45, 6447–6460.
  111. Yu, D.; Xue, Y.; Dai, L. Vertically aligned carbon nanotube arrays co-doped with phosphorus and nitrogen as efficient metal-free electrocatalysts for oxygen reduction. J. Phys. Chem. Lett. 2012, 3, 2863–2870.
  112. Jin, Z.; Nie, H.; Yang, Z.; Zhang, J.; Liu, Z.; Xu, X.; Huang, S. Metal-free selenium doped carbon nanotube/graphene networks as a synergistically improved cathode catalyst for oxygen reduction reaction. Nanoscale 2012, 4, 6455–6460.
  113. Sumpter, B.G.; Meunier, V.; Romo-Herrera, J.M.; Cruz-Silva, E.; Cullen, D.A.; Terrones, H.; Smith, D.J.; Terrones, M. Nitrogen-mediated carbon nanotube growth: Diameter reduction, metallicity, bundle dispersability, and bamboo-like structure formation. ACS Nano 2007, 1, 369–375.
  114. Chizari, K.; Janowska, I.; Houllé, M.; Florea, I.; Ersen, O.; Romero, T.; Bernhardt, P.; Ledoux, M.J.; Pham-Huu, C. Tuning of nitrogen-doped carbon nanotubes as catalyst support for liquid-phase reaction. Appl. Catal. A Gen. 2010, 380, 72–80.
  115. Chen, G.X.; Zhang, J.M.; Wang, D.D.; Xu, K.W. First-principles study of palladium atom adsorption on the boron- or nitrogen-doped carbon nanotubes. Phys. B Condens. Matter 2009, 404, 4173–4177.
  116. Rajala, T.; Kronberg, R.; Backhouse, R.; Buan, M.E.M.; Tripathi, M.; Zitolo, A.; Jiang, H.; Laasonen, K.; Susi, T.; Jaouen, F.; et al. A platinum nanowire electrocatalyst on single-walled carbon nanotubes to drive hydrogen evolution. Appl. Catal. B Environ. 2020, 265, 118582.
  117. Tsai, M.C.; Yeh, T.K.; Tsai, C.H. An improved electrodeposition technique for preparing platinum and platinum–ruthenium nanoparticles on carbon nanotubes directly grown on carbon cloth for methanol oxidation. Electrochem. Commun. 2006, 8, 1445–1452.
  118. Zhang, l.; Fang, Z.; Zhao, G.C.; Wei, X.W. Electrodeposited Platinum Nanoparticles on the Multi-Walled Carbon Nanotubes and its Electrocatalytic for Nitric Oxide. Int. J. Electrochem. Sci. 2008, 3, 746–754.
  119. Chen, X.; Li, N.; Eckhard, K.; Stoica, L.; Xia, W.; Assmann, J.; Muhler, M.; Schuhmann, W. Pulsed electrodeposition of Pt nanoclusters on carbon nanotubes modified carbon materials using diffusion restricting viscous electrolytes. Electrochem. Commun. 2007, 9, 1348–1354.
  120. Xiao, F.; Mo, Z.; Zhao, F.; Zeng, B. Ultrasonic-electrodeposition of gold–platinum alloy nanoparticles on multi-walled carbon nanotubes–ionic liquid composite film and their electrocatalysis towards the oxidation of nitrite. Electrochem. Commun. 2008, 10, 1740–1743.
  121. Huang, J.; Xie, Q.; Tan, Y.; Fu, Y.; Su, Z.; Huang, Y.; Yao, S. Preparation of Pt/multiwalled carbon nanotubes modified Au electrodes via Pt–Cu co-electrodeposition/Cu stripping protocol for high-performance electrocatalytic oxidation of methanol. Mater. Chem. Phys. 2009, 118, 371–378.
  122. Lorençon, E.; Ferlauto, A.S.; de Oliveira, S.; Miquita, D.R.; Resende, R.R.; Lacerda, R.G.; Ladeira, L.O. Direct production of carbon nanotubes/metal nanoparticles hybrids from a redox reaction between metal ions and reduced carbon nanotubes. ACS Appl. Mater. Interfaces 2009, 1, 2104–2106.
  123. Huang, J.Y.; Ding, F.; Yakobson, B.I.; Lu, P.; Qi, L.; Li, J. In situ observation of graphene sublimation and multi-layer edge reconstructions. Proc. Natl. Acad. Sci. USA 2009, 106, 10103–10108.
  124. Zhu, Y.; Murali, S.; Cai, W.; Li, X.; Suk, J.W.; Potts, J.R.; Ruoff, R.S. Correction: Graphene and Graphene Oxide: Synthesis, Properties, and Applications. Adv. Mater. 2010, 22, 5226.
  125. Liu, M.; Hof, F.; Moro, M.; Valenti, G.; Paolucci, F.; Pénicaud, A. Carbon supported noble metal nanoparticles as efficient catalysts for electrochemical water splitting. Nanoscale 2020, 12, 20165–20170.
  126. Yang, N.; Swain, G.M.; Jiang, X. Nanocarbon electrochemistry and electroanalysis: Current status and future perspectives. Electroanalysis 2016, 28, 27–34.
  127. Huang, X.; Yin, Z.; Wu, S.; Qi, X.; He, Q.; Zhang, Q.; Yan, Q.; Boey, F.; Zhang, H. Graphene-based materials: Synthesis, characterization, properties, and applications. Small 2011, 7, 1876–1902.
  128. Huang, X.; Qi, X.; Boey, F.; Zhang, H. Graphene-based composites. Chem. Soc. Rev. 2012, 41, 666–686.
  129. Li, X.; Cai, W.; An, J.; Kim, S.; Nah, J.; Yang, D.; Piner, R.; Velamakanni, A.; Jung, I.; Tutuc, E.; et al. Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils. Science 2009, 324, 1312–1314.
  130. Lotya, M.; Hernandez, Y.; King, P.J.; Smith, R.J.; Nicolosi, V.; Karlsson, L.S.; Blighe, F.M.; De, S.; Wang, Z.; McGovern, I.T.; et al. Liquid Phase Production of Graphene by Exfoliation of Graphite in Surfactant/Water Solutions. J. Am. Chem. Soc. 2009, 131, 3611–3620.
  131. Farooqui, U.; Ahmad, A.; Hamid, N. Graphene oxide: A promising membrane material for fuel cells. Renew. Sustain. Energy Rev. 2018, 82, 714–733.
  132. Arukula, R.; Vinothkannan, M.; Kim, A.R.; Yoo, D.J. Cumulative effect of bimetallic alloy, conductive polymer and graphene toward electrooxidation of methanol: An efficient anode catalyst for direct methanol fuel cells. J. Alloy. Compd. 2019, 771, 477–488.
  133. Su, C.; Loh, K.P. Carbocatalysts: Graphene Oxide and Its Derivatives. Acc. Chem. Res. 2013, 46, 2275–2285.
  134. Zhao, H.; Yang, J.; Wang, L.; Tian, C.; Jiang, B.; Fu, H. Fabrication of a palladium nanoparticle/graphene nanosheet hybrid via sacrifice of a copper template and its application in catalytic oxidation of formic acid. Chem. Commun. 2011, 47, 2014–2016.
  135. Chen, X.; Wu, G.; Chen, J.; Chen, X.; Xie, Z.; Wang, X. Synthesis of “clean” and well-dispersive Pd nanoparticles with excellent electrocatalytic property on graphene oxide. J. Am. Chem. Soc. 2011, 133, 3693–3695.
  136. Chen, Y.; Yang, X.; Kitta, M.; Xu, Q. Monodispersed Pt nanoparticles on reduced graphene oxide by a non-noble metal sacrificial approach for hydrolytic dehydrogenation of ammonia borane. Nano Res. 2017, 10, 3811–3816.
  137. Jeong, D.W.; Park, S.; Choi, W.J.; Bae, G.; Chung, Y.J.; Yang, C.S.; Lee, Y.K.; Kim, J.J.; Park, N.; Lee, J.O. Electron-transfer transparency of graphene: Fast reduction of metal ions on graphene-covered donor surfaces. Phys. Status Solidi RRL 2015, 9, 180–186.
  138. Iqbal, M.; Li, C.; Jiang, B.; Hossain, M.S.A.; Islam, M.T.; Henzie, J.; Yamauchi, Y. Tethering mesoporous Pd nanoparticles to reduced graphene oxide sheets forms highly efficient electrooxidation catalysts. J. Mater. Chem. A 2017, 5, 21249–21256.
  139. Li, S.S.; Zheng, J.N.; Ma, X.; Hu, Y.Y.; Wang, A.J.; Chen, J.R.; Feng, J.J. Facile synthesis of hierarchical dendritic PtPd nanogarlands supported on reduced graphene oxide with enhanced electrocatalytic properties. Nanoscale 2014, 6, 5708–5713.
  140. Vilian, A.E.; Hwang, S.K.; Kwak, C.H.; Oh, S.Y.; Kim, C.Y.; Lee, G.w.; Lee, J.B.; Huh, Y.S.; Han, Y.K. Pt-Au bimetallic nanoparticles decorated on reduced graphene oxide as an excellent electrocatalysts for methanol oxidation. Synth. Met. 2016, 219, 52–59.
  141. Hassan, H.M.; Abdelsayed, V.; Abd El Rahman, S.K.; AbouZeid, K.M.; Terner, J.; El-Shall, M.S.; Al-Resayes, S.I.; El-Azhary, A.A. Microwave synthesis of graphene sheets supporting metal nanocrystals in aqueous and organic media. J. Mater. Chem. 2009, 19, 3832–3837.
  142. Bai, R.G.; Muthoosamy, K.; Zhou, M.; Ashokkumar, M.; Huang, N.M.; Manickam, S. Sonochemical and sustainable synthesis of graphene-gold (G-Au) nanocomposites for enzymeless and selective electrochemical detection of nitric oxide. Biosens. Bioelectron. 2017, 87, 622–629.
  143. Huang, Y.X.; Xie, J.F.; Zhang, X.; Xiong, L.; Yu, H.Q. Reduced graphene oxide supported palladium nanoparticles via photoassisted citrate reduction for enhanced electrocatalytic activities. ACS Appl. Mater. Interfaces 2014, 6, 15795–15801.
  144. Zhou, X.; Huang, X.; Qi, X.; Wu, S.; Xue, C.; Boey, F.Y.C.; Yan, Q.; Chen, P.; Zhang, H. In Situ Synthesis of Metal Nanoparticles on Single-Layer Graphene Oxide and Reduced Graphene Oxide Surfaces. J. Phys. Chem. C 2009, 113, 10842–10846.
  145. Qin, X.; Li, Q.; Asiri, A.M.; Al-Youbi, A.O.; Sun, X. One-pot synthesis of Au nanoparticles/reduced graphene oxide nanocomposites and their application for electrochemical H2O2, glucose, and hydrazine sensing. Gold Bull. 2014, 47, 3–8.
  146. Yang, M.Q.; Pan, X.; Zhang, N.; Xu, Y.J. A facile one-step way to anchor noble metal (Au, Ag, Pd) nanoparticles on a reduced graphene oxide mat with catalytic activity for selective reduction of nitroaromatic compounds. CrystEngComm 2013, 15, 6819–6828.
  147. Zou, C.; Yang, B.; Bin, D.; Wang, J.; Li, S.; Yang, P.; Wang, C.; Shiraishi, Y.; Du, Y. Electrochemical synthesis of gold nanoparticles decorated flower-like graphene for high sensitivity detection of nitrite. J. Colloid Interface Sci. 2017, 488, 135–141.
  148. Liu, S.; Tian, N.; Xie, A.Y.; Du, J.H.; Xiao, J.; Liu, L.; Sun, H.Y.; Cheng, Z.Y.; Zhou, Z.Y.; Sun, S.G. Electrochemically seed-mediated synthesis of sub-10 nm tetrahexahedral Pt nanocrystals supported on graphene with improved catalytic performance. J. Am. Chem. Soc. 2016, 138, 5753–5756.
  149. Sheng, H.; Wei, M.; D’Aloia, A.; Wu, G. Heteroatom polymer-derived 3D high-surface-area and mesoporous graphene sheet-like carbon for supercapacitors. ACS Appl. Mater. Interfaces 2016, 8, 30212–30224.
  150. Luo, L.; Fu, C.; Yang, F.; Li, X.; Jiang, F.; Guo, Y.; Zhu, F.; Yang, L.; Shen, S.; Zhang, J. Composition-graded Cu–Pd nanospheres with Ir-doped surfaces on N-doped porous graphene for highly efficient ethanol electro-oxidation in alkaline media. ACS Catal. 2019, 10, 1171–1184.
  151. Qiu, X.; Yan, X.; Cen, K.; Sun, D.; Xu, L.; Tang, Y. Achieving highly electrocatalytic performance by constructing holey reduced graphene oxide hollow nanospheres sandwiched by interior and exterior platinum nanoparticles. ACS Appl. Energy Mater. 2018, 1, 2341–2349.
  152. Kumar, R.; Oh, J.H.; Kim, H.J.; Jung, J.H.; Jung, C.H.; Hong, W.G.; Kim, H.J.; Park, J.Y.; Oh, I.K. Nanohole-structured and palladium-embedded 3D porous graphene for ultrahigh hydrogen storage and CO oxidation multifunctionalities. ACS Nano 2015, 9, 7343–7351.
  153. Kumar, R.; Singh, R.K.; Vaz, A.R.; Savu, R.; Moshkalev, S.A. Self-assembled and one-step synthesis of interconnected 3D network of Fe3O4/reduced graphene oxide nanosheets hybrid for high-performance supercapacitor electrode. ACS Appl. Mater. Interfaces 2017, 9, 8880–8890.
  154. Qiu, X.; Li, T.; Deng, S.; Cen, K.; Xu, L.; Tang, Y. A General Strategy for the Synthesis of PtM (M= Fe, Co, Ni) Decorated Three-Dimensional Hollow Graphene Nanospheres for Efficient Methanol Electrooxidation. Chem.–A Eur. J. 2018, 24, 1246–1252.
  155. Yao, C.; Zhang, Q.; Su, Y.; Xu, L.; Wang, H.; Liu, J.; Hou, S. Palladium nanoparticles encapsulated into hollow N-doped graphene microspheres as electrocatalyst for ethanol oxidation reaction. ACS Appl. Nano Mater. 2019, 2, 1898–1908.
  156. Yu, K.; Lin, Y.; Fan, J.; Li, Q.; Shi, P.; Xu, Q.; Min, Y. Ternary N, S, and P-doped hollow carbon spheres derived from polyphosphazene as Pd supports for ethanol oxidation reaction. Catalysts 2019, 9, 114.
  157. Zhang, H.; Liu, G.; Shi, L.; Ye, J. Single-atom catalysts: Emerging multifunctional materials in heterogeneous catalysis. Adv. Energy Mater. 2018, 8, 1701343.
  158. Liu, J.; Ma, Q.; Huang, Z.; Liu, G.; Zhang, H. Recent progress in graphene-based noble-metal nanocomposites for electrocatalytic applications. Adv. Mater. 2019, 31, 1800696.
  159. Stambula, S.; Gauquelin, N.; Bugnet, M.; Gorantla, S.; Turner, S.; Sun, S.; Liu, J.; Zhang, G.; Sun, X.; Botton, G.A. Chemical structure of nitrogen-doped graphene with single platinum atoms and atomic clusters as a platform for the PEMFC electrode. J. Phys. Chem. C 2014, 118, 3890–3900.
  160. Yan, H.; Cheng, H.; Yi, H.; Lin, Y.; Yao, T.; Wang, C.; Li, J.; Wei, S.; Lu, J. Single-atom Pd1/graphene catalyst achieved by atomic layer deposition: Remarkable performance in selective hydrogenation of 1, 3-butadiene. J. Am. Chem. Soc. 2015, 137, 10484–10487.
  161. Detavernier, C.; Dendooven, J.; Sree, S.P.; Ludwig, K.F.; Martens, J.A. Tailoring nanoporous materials by atomic layer deposition. Chem. Soc. Rev. 2011, 40, 5242–5253.
  162. Sun, S.; Zhang, G.; Gauquelin, N.; Chen, N.; Zhou, J.; Yang, S.; Chen, W.; Meng, X.; Geng, D.; Banis, M.N.; et al. Single-atom catalysis using Pt/graphene achieved through atomic layer deposition. Sci. Rep. 2013, 3, 1–9.
  163. Yan, H.; Lin, Y.; Wu, H.; Zhang, W.; Sun, Z.; Cheng, H.; Liu, W.; Wang, C.; Li, J.; Huang, X.; et al. Bottom-up precise synthesis of stable platinum dimers on graphene. Nat. Commun. 2017, 8, 1070.
  164. Bulushev, D.A.; Zacharska, M.; Lisitsyn, A.S.; Podyacheva, O.Y.; Hage, F.S.; Ramasse, Q.M.; Bangert, U.; Bulusheva, L.G. Single atoms of Pt-group metals stabilized by N-doped carbon nanofibers for efficient hydrogen production from formic acid. ACS Catal. 2016, 6, 3442–3451.
  165. Zhang, C.; Sha, J.; Fei, H.; Liu, M.; Yazdi, S.; Zhang, J.; Zhong, Q.; Zou, X.; Zhao, N.; Yu, H.; et al. Single-atomic ruthenium catalytic sites on nitrogen-doped graphene for oxygen reduction reaction in acidic medium. ACS Nano 2017, 11, 6930–6941.
  166. Choi, C.H.; Kim, M.; Kwon, H.C.; Cho, S.J.; Yun, S.; Kim, H.T.; Mayrhofer, K.J.; Kim, H.; Choi, M. Tuning selectivity of electrochemical reactions by atomically dispersed platinum catalyst. Nat. Commun. 2016, 7, 10922.
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