Phototransformations of TiO 2 /Ag 2 O composites and their influence on photocatalytic water splitting accompanied by methanol photoreforming.

This work aimed to revise the mechanism of photocatalytic activity of the TiO 2 /Ag 2 O system in photocatalytic water splitting accompanied by methanol photoreforming. The transformation of Ag 2 O 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 TiO 2 , on its optoelectronic properties was analysed through inter alia spectroelectrochemical measurements. The photoreduced material exhibited a significantly shifted position of the TiO 2 conduction band edge. Surface photovoltage measurements revealed the lack of photoinduced exchange of electrons between TiO 2 and Ag 2 O, 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 CO 2 from methanol photoreforming was analysed. It was found that fully formed AgNPs exhibit improved efficiency in the production of H 2 , whereas the Ag 2 O phototransformation, resulting in the growth of AgNPs, promotes simultaneously ongoing photoreforming of methanol.