Phototransformations of TiO2/Ag2O composites and their influence on photocatalytic water splitting accompanied by methanol photoreforming

Abstract

This work aimed to revise the mechanism of photocatalytic activity of the TiO₂/Ag₂O system in photocatalytic water splitting accompanied by methanol photoreforming. The transformation of Ag₂O into silver nanoparticles (AgNPs) during photocatalytic water splitting/methanol photoreforming was monitored using XRD, XPS, SEM, UV-vis, and DRS techniques. The impact of AgNPs, grown on TiO₂, on its optoelectronic properties was analysed through inter alia spectroelectrochemical measurements. The photoreduced material exhibited a significantly shifted position of the TiO₂ conduction band edge. Surface photovoltage measurements revealed the lack of photoinduced exchange of electrons between TiO₂ and Ag₂O, indicating the absence of an efficient p–n junction. Furthermore, the impact of chemical and structural changes in the photocatalytic system on the production of CO and CO₂ from methanol photoreforming was analysed. It was found that fully formed AgNPs exhibit improved efficiency in the production of H₂, whereas the Ag₂O phototransformation, resulting in the growth of AgNPs, promotes simultaneously ongoing photoreforming of methanol.