Controllable Distribution of Oxygen Vacancies in Grain Boundaries of p‐Si/TiO<sub>2</sub> Heterojunction Photocathodes for Solar Water Splitting
Huimin Li, Tuo Wang, Shanshan Liu, Zhibin Luo, Lulu Li, Huaiyuan Wang, Zhi‐Jian Zhao, Jinlong Gong
Abstract
Abstract Silicon is a promising photocathode material in photoelectrochemical water splitting for hydrogen production, but it is primarily limited by photocorrosion in aqueous electrolytes. As an extensively used protective material, crystalline TiO 2 could protect Si photoelectrode against corrosion. However, a large number of grain boundaries (GBs) in polycrystalline TiO 2 would induce excessive recombination centers, impeding the carrier transport. This paper describes the introduction of oxygen vacancies (O vac ) with controllable spatial distribution for GBs to promote carrier transport. Two kinds of O vac distribution, O vac along GBs and O vac inside grains, are compared, where the latter one is demonstrated to facilitate carrier transport owing to the formation of tunneling paths across GBs. Consequently, a simple p‐Si/TiO 2 /Pt heterojunction photocathode with controllable O vac distribution in TiO 2 shows a +400 mV onset potential shift and yields an applied bias photon‐to‐current efficiency of 5.9 %, which is the best efficiency reported among silicon photocathodes except for silicon homojunction.