Mechanistic Principles of Photocatalytic Reaction

Abstract

As developments in semiconductor photocatalysis flourish, profound success is being recorded in the elucidation of reactivity vis-à-vis mechanism. The mechanism of photocatalytic reactions lies between two limits. From viewpoint of photochemical kinetics, the reaction mechanism will be controlled by the properties of light and consequences of light absorption. However as mass transfer dominates, the process will be controlled by the non-catalytic diffusion mechanism. This chapter highlights both diffusion and photocatalytically controlled kinetics in semiconductor-based heterogeneous regimes. In the final place, some conventional analytical methods for validation of photocatalytic reaction mechanism are discussed.

Assessing the Role of Pt Clusters on TiO2 (P25) on the Photocatalytic Degradation of Acid Blue 9 and Rhodamine B

“…Getting insight into the working principles of the developed catalyst will especially help further developments such as combining materials in order to make even more active catalysts. In order to degrade organic pollutants using photocatalysis, generally four steps take place: 7,8 (1) Adsorption of the reactants (pollutant, O 2 , and H 2 O) on the surface (2) Light absorption and generation of charge carriers (e − / h + ) (3) Redox reaction on the surface creating hydroxyl radicals, superoxide radicals, or directly oxidizing the pollutant (4) Desorption of products from the surface Upon light excitation of the photocatalysts, an electron (e − ) is excited to the conduction band (CB), leaving a hole (h + ) in the valence band (VB). Those excited charges generate reactive oxygen species (ROS) such as superoxide radicals (O 2 − *) from e − CB and hydroxyl radicals (OH*) from h VB + .…”

“…Getting insight into the working principles of the developed catalyst will especially help further developments such as combining materials in order to make even more active catalysts. In order to degrade organic pollutants using photocatalysis, generally four steps take place: , Adsorption of the reactants (pollutant, O 2 , and H 2 O) on the surface Light absorption and generation of charge carriers (e – /h + ) Redox reaction on the surface creating hydroxyl radicals, superoxide radicals, or directly oxidizing the pollutant Desorption of products from the surface …”

A novel magnetic HS−-adsorptive nanocomposite photocatalyst (rGO/CoMn2O4–MgFe2O4) for hydrogen fuel production using H2S feed

“…30,31 Since H 2 S photoconversion is a heterogeneous process and the conversion does not occur until the reactant species adsorb on the photocatalyst surface, the surface area plays a crucial role in the photocatalytic activity. 21,[32][33][34] To increase the photocatalyst surface area and improve its sorption capability [photon absorption/harnessing and reactant adsorption], reduced graphene oxide (rGO) was employed and the ternary magnetic rGO/ CoMn 2 O 4 -MgFe 2 O 4 nanocomposite was synthesized for the first time and applied as an efficient photocatalyst for the production of hydrogen fuel using H 2 S feed. Graphene oxide (GO) was synthesized through a Hummers' method with some modifications.…”

Synthesis of a Rationally Designed Multi-Component Photocatalyst Pt:SiO2:TiO2(P25) with Improved Activity for Dye Degradation by Atomic Layer Deposition

“…Factors such as adsorption of the reactants for the ROS formation have been demonstrated to play a crucial role in the enhancement of the photocatalytic activity [ 15 , 16 , 17 ]. Overall, the photocatalytic mechanism gives four different points to tackle for making improved materials [ 18 , 19 ]: Adsorption of reactants. Creation of charge carriers by light absorption.…”