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Green Applications of Photocatalysis, Photo-Thermocatalysis and Photo-Electrocatalysis
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Topic review
Updated time: 14 Sep 2021
Submitted by: Joao Gomes
Definition: The continuous increase of the world’s population results in an increased demand for energy drastically from the industrial and domestic sectors as well. Moreover, the current public awareness regarding issues such as pollution and overuse of petroleum fuel has resulted in the development of research approaches concerning alternative renewable energy sources. Amongst the various options for renewable energies used in transportation systems, biodiesel is considered the most suitable replacement for fossil-based diesel. In what concerns the industrial application for biodiesel production, homogeneous catalysts such as sodium hydroxide, potassium hydroxide, sulfuric acid, and hydrochloric acid are usually selected, but their removal after reaction could prove to be rather complex and sometimes polluting, resulting in increases on the production costs. Therefore, there is an open field for research on new catalysts regarding biodiesel production, which can comprise heterogeneous catalysts. Apart from that, there are other alternatives to these chemical catalysts. Enzymatic catalysts have also been used in biodiesel production by employing lipases as biocatalysts. For economic reasons, and reusability and recycling, the lipases urged to be immobilized on suitable supports, thus the concept of heterogeneous biocatalysis comes in existence. Just like other heterogeneous catalytic materials, this one also presents similar issues with inefficiency and mass-transfer limitations. A solution to overcome the said limitations can be to consider the use of nanostructures to support enzyme immobilization, thus obtaining new heterogeneous biocatalysts.
Topic review
Updated time: 22 Apr 2021
Submitted by: Michalis Konsolakis
Definition: The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at nanometer scale can exert an intense impact not only on the inherent reactivity of catalyst’s counterparts but also on their interfacial interactions, opening up new horizons for the development of highly active and robust materials. The main implications of ceria nanoparticles’ shape engineering (rods, cubes, polyhedra) in catalysis are revealed, on the ground of some of the most pertinent heterogeneous reactions, such as CO2 hydrogenation, CO oxidation, and N2O decomposition. It is clearly revealed that shape functionalization can remarkably affect the intrinsic features and in turn the reactivity of ceria nanoparticles. More importantly, by combining ceria nanoparticles (CeO2 NPs) of specific architecture with various transition metals (e.g., Cu, Fe, Co, Ni) remarkably active multifunctional composites can be obtained due mainly to the synergistic metal-ceria interactions, providing the design principles of earth-abundant metal oxide catalysts for various real-life environmental and energy applications.
Topic review
Updated time: 29 Jul 2021
Submitted by: Stuart McMichael
Definition: Now and in the coming years, how we use and treat water, greywater and wastewater will become more important. A suitably designed photoelectrocatalytic (PEC) reactor is one potential solution. The photoexcitation of suitable semiconducting materials in aqueous environments can lead to the production of reactive oxygen species (ROS). ROS can inactivate microorganisms and degrade a range of chemical compounds. In the case of heterogeneous photocatalysis, semiconducting materials may suffer from fast recombination of electron–hole pairs and require post-treatment to separate the photocatalyst when a suspension system is used. To reduce recombination and improve the rate of degradation, an externally applied electrical bias can be used where the semiconducting material is immobilised onto an electrically conducive support and connected to a counter electrode. These electrochemically assisted photocatalytic systems have been termed “photoelectrocatalytic” (PEC). The term is stated in the IUPAC Recommendations 2011 as “electrochemically assisted photocatalysis. The role of the photocatalyst is played by a photoelectrode, often a semiconductor”. A short description of photocatalysis is included as it can be beneficial for those unfamiliar with the topic, before moving onto PEC.
Topic review
Updated time: 24 Sep 2021
Submitted by: ADNAN ALI
Definition: Materials crystalizing in the perovskite crystal structure are common crystals that are currently employed for multiples applications, including transistors, solar cells, light-emitting devices, memories, catalysts, and superconductors.One of the biggest players within the perovskite structures is the family of oxide perovskites. This is a prominent family with the general formula of ABO3, where A commonly designates an alkaline or rare earth metal cation, occupying the 12-fold coordinated cuboctahedral cages of the oxygen sub-lattice, and B stands for a transition-metal cation (e.g., Fe, Ni, Mn, Co, Cu, or Ti) coordinated with six oxygen atoms in an octahedral coordination. In fact, in the perovskite structure, distortions frequently occur due to the deviation from ideal values of ionic size ratios between the different A, B, and O sites of the crystal. In addition, A or B cations may have distinctive sizes and valences that could result into oxygen non-stoichiometry, involving both oxygen excess and/or oxygen deficiency.
Topic review
Updated time: 30 Mar 2021
Submitted by: Anuja Bokare
Definition: TiO2 is the most widely used photocatalyst in many energy and environmental applications. This entry describes the basic structure and properties of TiO2 as a nanomaterials. It also enlists the special properties of TiO2 which make it a best candidate for photocatalysis reaction. It also explains the drawbacks of TiO2 nanomaterials along with the strategies to overcome those.
Topic review
Updated time: 31 Mar 2021
Submitted by: Hong Sohn
Definition: A Transparent Conducting Oxides (TCO) is a wide band-gap semiconductor that has high concentration of free electrons in its conduction band.