Role of Surface Structure in the Mechanism of Semiconductor Photocatalysts: Overlooked Key for Structure-activity Correlation

The importance of photocatalytic reactions using semiconductors, used in applications such as water decomposition, carbon dioxide reduction and fixation and organic matter decomposition, goes without saying. Numerous studies on photocatalytic reactions have been reported, many aiming to elucidate the correlation between the structure and activity of photocatalysts, including the development of new materials. Most of these studies involved "thermodynamic" analysis based on comparisons of the bulk structure, which determines the energy of the semiconductor's band gap, conduction-band bottom and valence-band top. However, considering that photocatalytic activity is the rate of the photoreaction, thermodynamic structural analysis only provides information on whether or not the reaction can proceed.In photocatalytic reactions, excited electrons and holes generated by the photocatalyst's light absorption reduce and oxidize the adsorbed substrates on the photocatalyst surface, respectively. Therefore, it is thought that the interfacial electron-transfer process, in which excited electrons and holes are transferred from the surface to the adsorbed substrates, governs the reaction rate (efficiency). In many photocatalytic reaction systems, attempts have been made to determine the activation energy from the temperature dependence of the reaction rate. However, in most systems, the activation energy obtained relates to the diffusion of reactants to the surface. In other words, the charge transfer process in photocatalytic reactions is not governed by the activation energy, unlike in ordinary chemical reactions.It is well known that loaded platinum or manganese oxide to photocatalysts improves their activity for hydrogen or oxygen evolution, respectively. This is because these elements act as charge-transfer "paths" for excited electrons and holes. However, the nature of the excited electron path, in particular, has not been discussed for bare (not cocatalyst loaded) photocatalysts until now. In other words, understanding the surface structure as a charge-transfer path, which has been overlooked so far, is of great importance for further research of photocatalytic reactions, as well as electrode reaction and/or catalysis. This Research Topic aims to deepen the discussion on the role of the surface structure of materials in the charge-transfer processes.We invite contributions that address:o Analysis of distribution of electron traps as a surface path for electrons of photocatalysts, photoelectrodes or catalystso Study on the change of rate, selectivity or the other performances by controlling the exposed crystalline lattice(s) or the particle morphologyo Role of surface amorphous or impurity layers on the efficiency of charge transfer at the surfaceo Analysis on the path for interparticle charge transfero Theoretical studies on the surface structure for understanding the charge-transfer pathsThis collection will provide critical insights into how precise control of charge-transfer paths can unlock new levels of efficiency in charge-transfer process in photocatalysis, electrode reaction and catalysis. Topic editors: Bunsho Ohtani Source: https://www.frontiersin.org/research-topics/79725/role-of-surface-structure-in-the-mechanism-of-semiconductor-photocatalysts-overlooked-key-for-structure-activity-correlation