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.