1.2. Characterization
Different approaches have been used to study the different surface characteristics and chemical structures of GFN-TiO
2 (
Table 1). Scanning electron microscopy (SEM)
[27][28][29][30][31][151,163,164,165,166], transmission electron microscopy (TEM)
[28][30][31][163,165,166], and atomic force microscopy (AFM)
[29][164] are typically used for morphological observation. The results indicated that GFN was well embedded or covered by TiO
2. The composites with lower GFN ratios tended to aggregate, forming large spherical-shaped particles
[27][28][29][30][31][151,163,164,165,166]. Adding graphene increased and then decreased the crystallite size of composites. The initial augmentation was caused by accelerating the crystallization of TiO
2. Excess H
2O by the dispersion of graphene promoted the hydrolysis of titanium isopropoxide. Continuously increasing the graphene content enhanced incorporation between the nucleation centers, delaying crystallization and decreasing the crystallite size
[27][28][29][30][31][151,163,164,165,166]. Composites could exhibit non-spherical structures, such as platelet- or flower-like morphology with elevated GFN ratios
[27][28][29][30][31][32][151,163,164,165,166,167]. The TEM studies indicated that GFN-TiO
2 exhibited two-dimensional structures
[28][30][31][32][163,165,166,167]. An AFM study showed a significant increase in the thickness when excess graphene was added during composite preparation
[29][164].
Table 1. Methods and outcomes of characterization of TiO2-graphene composites.
Category |
Technology |
Description |
Ref. |
Morphology |
Table 3. Removal of water-phase pollutants by GFN-TiO2 in selected studies.
|
Pollutant |
Catalyst |
Light Source |
SEM |
Spherical and non-spherical (platelet- or flower-like) shapes were observed with low and high GFN contents, respectively. |
[ | 27][28][29][30][31][32][151,163,164,165,166,167] |
TEM |
A fine dispersion of TiO2 in GFN with low- and nano-dimensions was reported. |
[28][30][31][32][163,165,166,167] |
AFM |
The thickness of GFN-TiO2 was increased to a scale of μm after preparation. |
[29][164] |
Chemical constitution |
FTIR |
The peak of Ti-O-Ti at 400–900 cm−1 was broadened or shifted by the influence of Ti-O-C. The signals of carbonyl and epoxy groups were reduced. |
[27][30][33][151,165,168] |
XPS |
The formation of C-Ti, O=C-O-Ti, and C-O-Ti bonds in GFN-TiO2 was observed. |
[28][163] [29][164] |
XRD |
The signals due to the presence of anatase and rutile were reported. |
[27][28][29][30][31][33][151,163,164,165,166,168] |
Raman |
The signals of both TiO2 and GFN were reported. The D/G intensity ratio of GFN-TiO2 was higher than that of GFN. |
[28][29][30][163,164,165] |
EPR |
The formation of hydroxyl and superoxide radical species was observed in GFN-TiO2. |
[31][166] |
Physicochemical properties |
Zeta potential |
The zeta potential of GFN-TiO2 ranged between those of GFN and TiO2. |
[29][164] |
TGA |
The irregular mass loss occurred at high temperatures. |
[29][164] |
BET |
The surface area of GFN-TiO2 was significantly increased at a certain ratio of GFN to TiO2. |
[27][28]163[29],164[30],165[33][151,,168] |
ACM |
The current density of GFN-TiO2 was significantly increased at a certain ratio of GFN to TiO. |
[33][168] |
PL |
The time dynamics of the TiO2-induced photoreduction of GO were observed. |
[34][169] |
UV-Vis |
A shift to larger wavelengths in the absorption edge was observed, indicating bandgap narrowing. |
[27][29][30][31][151[,16433,165,166],168] |
The chemical constitutions of GFN-TiO
2 were investigated by using Fourier transform infrared spectrometry (FTIR)
[27][30][33][151,165,168], X-ray photoelectron spectroscopy (XPS)
[28][29][163,164], X-ray diffraction (XRD)
[27][28][29][30][31][33][151,163,164,165,166,168], Raman spectrometry
[28][29][30][163,164,165], and electron paramagnetic resonance (EPR)
[31][166]. The FTIR results showed that the peak at 400–900 cm
−1 was broadened or shifted due to the presence of Ti-O-C in the Ti-O-Ti adsorption peak. The original peaks of carbonyl (C=O, 1700 cm
−1) and epoxy (C-O, 1230 cm
−1) groups of GO became negligible in the results of GFN-TiO
2 [27][30][33][151,165,168]. The XPS studies observed the bands of 463.2 and 458.5 eV in GFN-TiO
2, indicating a chemical state of Ti
4+ (TiO
2) in GFN-TiO
2 [28][29][163,164]. The identification of the peaks associated with Ti and GFN indicated the presence of Ti-C, O=C-O-Ti, and C-O-Ti in TiO
2-GFNs, as the C1s spectrum showed peaks attributed to C=C/C-C, epoxy (C-O)/hydroxyl (C-OH), and carboxyl groups (C(=O)OH).
[28][29][163,164]. The XRD studies have revealed the peak areas of anatase (25.3°) and a few rutile phases (27.4°), indicating TiO
2 was well mixed with GFN with limited phase changes
[27][28][29][30][31][33][151,163,164,165,166,168]. The Raman spectra of GFN-TiO
2 exhibited bands of E
g(1) (149 cm
−1), B
1g(1) (395 cm
−1), A
1g+B
1g(2) (517 cm
−1), and E
g(2) (640 cm
−1), attributable to the symmetric stretching and symmetric/asymmetric bending vibrations of the O-Ti-O group. The spectra also exhibited D (1384 cm
−1) and G bands (1596 cm
−1) of GFN, as the D/G intensity ratio was higher than that of GFN
[28][29][30][163,164,165]. The EPR study showed increasing intensities of the hydroxyl and superoxide radicals by increasing the ratio of GFN to TiO
2 [31][166].
Physicochemical properties including the surface charge, thermal stability, surface area, pore size, and pore volume of TiO
2-GFN have been investigated by Zeta potential analysis
[29][32][164,167], thermal gravity analysis (TGA)
[29][164], and Brunauer–Emmett–Teller (BET) analysis
[27][28][29][30][33][151,163,164,165,168], respectively. The nucleation of TiO
2 on GFN masked the functional groups on the surface and lowered the zeta potential of GFN-TiO
2 [29][32][164,167]. The TGA study showed a better heat resistance of GFN-TiO
2, as TiO
2 stabilized GO by the interaction between oxygen-containing groups of GFN and TiO
2 [29][164]. Most studies have indicated a higher surface area of GFN-TiO
2 compared to that of TiO
2 [27][28][29][30][33][151,163,164,165,168], whereas an opposite trend has also been reported in a few studies
[27][28][29][30][33][151,163,164,165,168]. GFN-TiO
2 typically exhibited mesopore size distribution with averages near 10 nm
[27][28][29][30][33][151,163,164,165,168].
Potentiostat, photoluminescence (PL), and ultraviolet-visible spectroscopy (UV-Vis) are useful tools to investigate the optical characteristics of GFN-TiO
2 [27][29][30][31][33][151,164,165,166,168]. A study has reported that an optimal ratio of GFN to TiO
2 increased the current density of GFN-TiO
2, because the two-dimensional conjugation structure of GFN accepted and transported the excited electron from TiO
2 [33][168]. Pallotti et al. used photoluminescence (PL) spectroscopy for real-time analysis to trace the time dynamics of the photoreduction of GO
[34][169]. It was found in real-time that the photocatalysis induced by the presence of TiO
2 contributed to GO photoreduction. By adding GFN into TiO
2, the absorption edge of GFN-TiO
2 displayed an increase in wavelength (known as redshift) that indicated a bandgap narrowing. Its light absorption intensity in the UV region was also increased
[27][29][30][31][33][151,164,165,166,168].
Table 2 lists some examples of TiO
2-GFN prepared for photocatalysis and battery storage.
Table 2. Properties of TiO2-GFN prepared for photocatalysis and battery storage in various studies.
Materials |
Average Size (nm) |
Functional Group |
Bandgap (eV) |
Wavelength (nm) |
Surface Area (m2/g) |
Reference |
Removal |
Ref. |
Graphene-TiO2 |
3.8 |
C-O, C=O, O=C-O, and O-Ti |
NA 1 |
600 |
Inorganic |
Cr(VI) (0.2 mM) |
GO-TiO2 | 176 |
(0.5 g/L) |
254 nm, 20 W, UV lamp |
90% |
[29][35][170] |
[ | 164 | ] |
Graphene-TiO2 |
~6 |
C-O and O-C=O |
NA |
NA |
252 |
[36][ |
Cr(VI)(10 mg/L) |
GO-TiO2 (0.5 g/L) | 158 | ] | |
365 nm, 8 W, UV lamp | 2 |
99% |
[ | 41 | ] | [174] |
GO-TiO2 |
NA |
C-O, Ti-O-Ti, Ti-O-C, and OH |
NA |
~800 |
69.2 |
[27][151] |
Organic |
Methylene blue (0.01 g/L) |
Graphene-TiO2 (0.75 g/L) |
365 nm, 100 W, high-pressure Hg lamp >400 nm, 500W, Xe lamp |
85% 65% |
[42][175] |
GO-Co-TiO2 |
NA |
C-O, C-N, O-C=O |
2.77 |
421 |
206 |
Rhodamine B (20 mg/L) |
Graphene-TiO2 (0.1 g/L) | [ | 37 | ] | [ | 109] |
11 W, low-pressure Hg lamp |
91% |
[ | 43 | ][176] |
GO-Ti |
NA |
Rhodamine B (20 mg/L) Norfloxacin (20 mg/L) | NA |
Aldicarb (10.5 mg/L) |
Graphene-TiO2 (1 g/L) |
>400 nm, Xe lamp2.9 |
~550 |
68.9 |
79.7% 86.2% 36.8% |
[35][170][38][171] |
rGO-TiO2 |
35 |
NA |
NA |
~360 |
212.75 |
Malachite green oxalate (13.1 mg/L) |
GO-TiO2 (0.2 g/L) | [ |
450 W, water-cooled Hg lamp |
80% |
[26][145] | 39][172] |
rGO-TiO2 |
~8 |
NA |
NA |
NA |
229 |
[40][157] 2 |
2.1. Water-Phase Pollutants
GFN-TiO
2 has been used for the photocatalytic removal of inorganic, organic, and biological pollutions in the water phase (
Table 3). The photocatalytic reduction of inorganic pollutants such as metal ions was one example. Jiang et al. investigated the reduction of Cr(VI) to Cr(III) in water by using GFN-TiO
2 [29][164]. The reduction rate constant was 0.0691 min
−1, exceeding that of using pure TiO
2 (0.0174 min
−1) by a factor of 3.9. In another Cr(VI) removal study, the Cr(VI) concentration was adsorbed (~55%) by using TiO
2-GO for 1 h, and with UV irradiation, nearly all Cr(VI) concentration was reduced in 7 h
[41][174]. In the same system using TiO
2 with UV irradiation, the Cr(VI) concentrations were limitedly adsorbed (23%) and reduced (30%).
Phenol (10 mg/L) |
rGO-TiO |
2 |
(5 g/L) |
310-400 nm, UV lamp |
Not given |
[ | 44 | ][177] |
2,4-D (15 mM) |
rGO-TiO2 (film) |
<320 nm, 450 W, Xe lamp |
~87% |
[45][178] |
Biological |
E. coli (106 CFU/mL), F. solani spores (103 CFU/mL) |
rGO-TiO2 (0.5 g/L) |
Sunlight |
~100% |
[46][179] |
E. coli, S.aureus, S.typhi, P. aeruginosa, B. subtilis, B. pumilus (106 CFU/mL) |
Graphene-Ag3PO4-TiO2 |
>420 nm, 350 W, Xe lamp |
~100% |
[47][180] |
E. coli (105–106 CFU/mL) |
GO-TiO2 (0.2 g/L) |
Xe lamp |
~100% |
[48][181] |
E. coli (106 CFU/mL) |
rGO-TiO2 (18 mg/L) |
>285 nm, UV-visible light; >420 nm, visible light |
~100% |
[49][182] |
Graphene-TiO
2 has been frequently investigated for its potentials for photocatalytic degradation of organic pollutants. Homolytic cleavage is typically the first chemical step in photodegradation. Free radicals are formed in this step and rapidly react with any oxygen present in the system. Li et al. investigated the photocatalytic activity of graphene-TiO
2 towards representative aqueous persistent organic pollutants (POPs)
[35][170]. The POPs included rhodamine B, norfloxacin, and aldicarb. The presence of graphene-TiO
2 significantly enhanced the removal of these POPs. While the compound concentrations were negligibly changed during pure photolysis, the presence of GFN-TiO
2 (0.86%
w/
w of graphene) resulted in 79.7% and 86.2% of total organic carbon (TOC) removal in the experiments of rhodamine B and norfloxacin, respectively, after 10 h of simulated sunlight irradiation (λ > 320 nm). Only 36.8% of TOC removal was observed in the aldicarb experiment after 25 h of visible light irradiation (λ > 400 nm). Zhang et al. investigated photodegradation of methylene blue by using TiO
2, carbon nanotube (CNT)-TiO
2, and graphene-TiO
2 as photocatalysts
[42][175]. In 1 h of UV irradiation, the removal efficiency of graphene-TiO
2 (85%) was significantly higher than TiO
2 (25%) and CNT-TiO
2 (71%). Using visible light reduced the performance of TiO
2 by a factor of 2, whereas the removal efficiency of graphene-TiO
2 (65%) was less affected.
GO represents another material that can work well with TiO
2, forming an efficient photocatalyst. Perera et al. compared the photodegradation of malachite green by using TiO
2, GO, and GO-TiO
2 [26][145]. Pseudo-first-order reactions were found when TiO
2 and GO-TiO
2 were used as catalysts. The rate constant of GO-TiO
2 (0.0674min
−1) exceeded that of TiO
2 (0.0281 min
−1) by a factor of 3. No photodegradation of malachite green occurred in the presence of GO. Another study investigated the photodegradation of rhodamine B by using three different nanosphere catalysts (amine-modified TiO
2–SiO
2, graphene-TiO
2, and GO-TiO
2–SiO
2)
[43][176]. In 1.5 h of irradiation, the removal efficiencies of graphene-TiO
2 (91%) and GO-TiO
2–SiO
2 (71%) were significantly higher than that of amine-modified TiO
2–SiO
2 (65%), indicating the synergistic effect between graphene or GO and TiO
2 for the enhanced catalysis activity.
The use of rGO-TiO
2 for the enhanced photocatalytic degradation of organic pollutants has also been demonstrated. Increasing the rGO content (from 0 to 1%
w/
w) in rGO-TiO
2 enhanced the photocatalytic decomposition of phenol (the 1st-order rate constant was increased from 0.0039 to 0.0048 min
−1)
[44][177]. rGO-TiO
2 exhibited fine photocatalytic performance after 5 cycles; however, a high rGO content (e.g., 5%
w/
w) potentially shielded the catalyst surface from light absorption, reducing the photocatalytic activity. Ng et al. investigated the removal of 2,4-dichlorophenolyxacetic acid (2,4-D), a commonly used herbicide, by photocatalytic reduction using TiO
2 and rGO-TiO
2 [45][178]. The pseudo-first-order rate constants of using TiO
2 and rGO-TiO
2 were 0.002 and 0.008 min
−1, respectively. Adding rGO increased the response of the photocurrent by a factor of 2 and the availability of 2,4-D on the surface of rGO-TiO
2, improving the whole photocatalytic reaction by a factor of 4.
Photocatalysis is capable of being adopted for use in many applications for disinfection in water matrices. Adding graphene in Ag
3PO
4-TiO
2 effectively improved the synergistic photocatalytic disinfection of
E. coli,
S.aureus,
S.typhi,
P. aeruginosa,
B. subtilis, and
B. pumilus [47][180]. Fernández-Ibáñez et al. have reported effective solar photocatalytic disinfection of
E. coli and
F. solani spores by using rGO–TiO
2. The presence of rGO significantly enhanced the performance of photocatalytic disinfection of
E. coli. Increasing rGO–TiO
2 from 0 to 500 mg/L accelerated the inactivation of
E. coli (10
6 colony-forming units (CFU)/mL) from more than 100 to 10 min and reduced the solar UV dosage needed from 123 to 11 kJ/m
2. Although both rGO-TiO
2 and pure TiO
2 exhibited excellent disinfection of
F. solani spores, rGO significantly reduced the solar energy required from 336.2 to 42.1 kJ/m
2 [46][179]. A certain ratio between rGO and TiO
2 significantly enhanced the photocatalytic disinfection under UV and solar irradiation
[49][182]. Another study has also demonstrated that GO, which effectively separated photo-generated e
−−h
+ pairs for more ▪OH production, improved the photocatalytic disinfection of
E. coli. In 30 min, the disinfection efficiencies of using pure TiO
2, GO, GO-TiO
2 were 39.27%, 73.82%, 99.60%, respectively
[48][181]. More detailed information concerning the removal of different inorganic, organic, and biological pollutants by using GFN-TiO
2 is available in
Table 28.
2.2. Air-Phase Pollutants
Similar to the removal of pollutants in the water phase, GFN-TiO
2 has been adopted for use in removing a wide range of air pollutants. Shorter contact times and the complexity of the heterogeneous photocatalytic reactions (e.g., photon absorbance and radical reactions) between pollutants and catalyst surfaces represent two typical challenges in this field
[27][151].
In the aspect of inorganic removal, the treatment efficiencies of gaseous NOx (from NO
(g) to NO
2(g) to NO
3−(s)) by using pure TiO
2, graphene-TiO
2, and rGO-TiO
2 were compared
[30][165]. An appreciable level of GFN (e.g., 0.01–0.1% graphene or rGO) in TiO
2 improved the removal of NOx under UV and visible light. The NOx removal efficiencies were 25.45%, 26.26–35.40%, and 39.38–42.86% by using TiO
2, graphene-TiO
2, and rGO-TiO
2 under UV light, respectively, while under visible light the removal efficiencies using TiO
2, graphene-TiO
2, and rGO-TiO
2 were 9.35%, 15.20–22.75%, and 19.88–22.34%, respectively. Giampiccolo et al. prepared graphene-TiO
2 by using the sol-gel method for electrochemical sensing and photocatalytic degradation of NOx in the air
[50][183]. Interestingly, the performances of graphene-TiO
2 prepared by using the same method but with different step orders were compared (adding graphene to the reaction before initiating the sol-gel reaction followed by annealing (GTiO
2S) and adding graphene to TiO
2 which had already been annealed (GTiO
2M)). The addition of graphene significantly improved the performance of the catalysts under solar irradiation (280–780 nm) (e.g., the pseudo-first-order rate constants of NOx removal by GTiO
2S, GTiO
2M, and TiO
2 were 6.7, 5.6, and 4.3/min, respectively.). The thermal treatment helped synthesize graphene and TiO
2 in more intimate contact and improved the exhibition. Besides NOx, photodegradation of CO by using GO-TiO
2, which was functionalized by attaching a cobalt (Co)-imidazole (Im) complex on GO, was investigated
[37][109]. The results revealed that the bandgaps of this functionalized GO-TiO
2 (with Co and Im), GO-TiO
2, and pure TiO
2 were 2.78, 2.96, and 3.10 eV, respectively. The removal efficiencies of CO and NOx were improved from 10% to 46% and from 16% to 51% when the catalyst was changed from TiO
2 to the functionalized GO-TiO
2, respectively. Xu et al. added graphene into TiO
2 to enhance the photocatalytic CO
2 conversion to chemical fuels
[51][184]. The addition of graphene inhibited the recombination of e
−−h
+ pairs and raised the surface temperature, improving the CO
2 conversion efficiency. The conversion rates of CO
2 to CH
4 and CO by using graphene-TiO
2 were higher than those using TiO
2 by factors of 5.1 and 2.8, respectively.
Studies have demonstrated the photocatalytic degradation of organic pollutants in the air phase by using GFN-TiO
2. Zang et al. have reported that adding graphene into TiO
2 with a specific ratio (e.g., 0.5%
w/
w) exhibited a synergetic effect on the UV light photodegradation of benzene (the mineralization rates of GFN-TiO
2 and TiO
2 were 76.2% in 10 h and 1.2% in 28 h, respectively). The adsorption of benzene and intermediates during benzene degradation negatively affecting TiO
2 adsorbing UV light was decreased by the presence of graphene. However, excess graphene could adsorb extra compounds and impact light absorption. Benzene removal was limitedly found when visible light was used
[31][166]. Similarly, in a study that focused on the photocatalytic degradation of acetone in the air, graphene-TiO
2 exhibited a better activity (the pseudo-1
st-order rate constant was 10.2 × 10
−3/min) exceeding that of pure TiO
2 (5.99 × 10
−3/min) by a factor of 1.7 and a good reproducibility after three cycles of illumination
[28][163].
Adding other materials to graphene-TiO
2 has been investigated to further enhance its photocatalytic activity. Photocatalytic degradation of formaldehyde by using graphene-TiO
2-Fe
3+ has been reported
[33][168]. Under UV light, both graphene-TiO
2-Fe
3+ and graphene-TiO
2 revealed better performances than pure TiO
2, as only the photolytic activity of graphene-Fe
3+-TiO
2 was better under visible light irradiation. The photocatalyst with a TiO
2/graphene ratio of 50 and a ratio of Fe
3+/graphene-TiO
2 of 0.12% revealed the optimal performance. Nitrogen has been doped into reduced graphene-TiO
2 to change the polarity of the catalyst and to influence the adsorption and photodegradation of polar acetaldehyde and nonpolar ethylene
[52][185]. Both reduced graphene-TiO
2 and N-doped reduced graphene-TiO
2 exhibited higher treatment efficiencies than pure TiO
2. One explanation was that nitrogen doping improved the polarity of the catalyst, further enhancing the removal efficiency of polar acetaldehyde.
The feasibility of adding GO into TiO
2 for the photocatalytic degradation of organic pollutants has been reported. A study used GO-TiO
2 as a photocatalyst to accelerate the degradation of benzene, toluene, ethylbenzene, and xylene (BTEX) in the air
[27][151]. Under UV irradiation, the removal of these compounds by using GO-TiO
2 was higher than that of using pure TiO
2 by a factor of 1.2, while GO-TiO
2 exhibited an excellent treatment efficiency exceeding that of pure TiO
2 by a factor of 12 under visible light irradiation. GO-TiO
2 has also been used for the photocatalytic degradation of methyl ethyl ketone in indoor air
[38][171]. The addition of GO in TiO
2 has improved the removal efficiency from 32.7% to 96.8% under visible light irradiation. Proper humidity (e.g., 40%), flow rate (e.g., 50 mL/min), and pollutant concentration (e.g., 30 ppmv) were the key to optimal performance. Note that the use of nanostructured membranes based on polymeric nanofibers using TiO
2 and GFNs, including GO, rGO, and few-layer graphene, for the photocatalytic oxidation of gas-phase methanol has been reported. As the photocatalytic activity was greatly changed by the membrane structure and affected by the affinity of GFN to the polymer matrix, rGO exhibited better performance due to its more enhanced electron mobility
[53][186].
Table 4 summarizes the applications of GFN-TiO
2 for the photodegradation of organic pollutants in the air in these studies.
Table 4 Removal of air-phase pollutants by GFN-TiO2 in selected studies.
|
Pollutant |
Catalyst |
Light Source |
Humidity or Flow Rate |
Removal |
Ref. |
Inorganic |
NOx (1 ppm) |
Graphene-TiO2 rGO-TiO2 |
15 W, UVA 8 W, visible light |
50% humidity, 3 L/min |
42% 49% |
[30][165] |
NOx (200 ppb) |
Graphene-TiO2 |
280–780 nm, 300 W, solar lamp |
1 L/min |
77% |
[50][183] |
CO (50 ppm) NOx (1 ppm) |
Graphene-TiO2 |
8 W, UV lamp |
0.2 L/min |
46% 51% |
[37][109] |
Organic |
Acetone (300 ± 20 ppm) |
Graphene-TiO2 |
365 nm, 15 W, UV lamp |
1 L/min |
~60% |
[28][163] |
Acetaldehyde (500 ppm) Ethylene (50 ppm) |
Graphene-TiO2 |
260 W, fluorescent lamp 500 W, Xenon lamp |
20 cm3/min |
~82% ~90% |
[52][185] |
Benzene (250 ppm) |
Graphene-TiO2 |
254 nm, 4 W, UV lamp |
20 mL/min |
6.4% |
[31][166] |
Formaldehyde (3000 ppm) |
Graphene-TiO2 |
365 nm, 8 W, black light blue lamp >420 nm, 8 W, fluorescent lamp |
Not specified |
50.3% 25.5% |
[33][168] |
Methanol (4,000 ppm) |
Graphene-TiO2 GO-TiO2 rGO-TiO2 |
254 nm, 16 W, UV lamp |
155 cm3/min |
80% 99% 99% |
[53][186] |
BTEX (1 ppm) |
GO-TiO2 |
400–720 nm, 8 W, daylight lamp |
55% humidity, 1 L/min |
96% |
[27][151] |
|
MEKT (30 ppm) |
GO-TiO2 |
80 W, Xe lamp |
40% humidity, 50 mL/min |
96.8% |
[38][171] |