Intrinsically Ru-Doped Suboxide TiO2 Nanotubes for Enhanced Photoelectrocatalytic H2 Generation

In the present research, we investigate the synergistic effects of Ru-doping and Ar/H2 reduction treatment on the photoelectrochemical water splitting performance and hydrogen evolution rate of TiO2 nanotube array photoelectrodes. The Ti–Ru alloy with 0.2 at. % Ru was used to grow anodic self-organized Ru-doped TiO2 nanotube layers. An ideal synergy between Ar/H2 reduction treatment and Ru-doping results in the extended absorption toward the visible light region and improved photoelectrocatalytic activity. The black Ru-doped TiO2–x photoanode's water splitting rate improves remarkably (∼ninefold) compared to the black TiO2–x sample (∼twofold). Moreover, the black Ru-doped TiO2–x photoanode shows a considerable increase in the H2 production rate (1.91 μmol h–1 cm–2) compared with the pristine TiO2 nanotube layer (0.044 μmol h–1 cm–2). We have also developed an ab initio model of pristine, Ru-doped, and Ru-doped hydrogenated TiO2 nanotubes to rationalize our experimental findings from the theoretical perspective.