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Controllable Distribution of Oxygen Vacancies in Grain Boundaries of p‐Si/TiO 2 Heterojunction Photocathodes for Solar Water Splitting
Author(s) -
Li Huimin,
Wang Tuo,
Liu Shanshan,
Luo Zhibin,
Li Lulu,
Wang Huaiyuan,
Zhao ZhiJian,
Gong Jinlong
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202014538
Subject(s) - photocathode , homojunction , water splitting , heterojunction , materials science , silicon , grain boundary , photoelectrochemistry , photoelectrochemical cell , optoelectronics , nanotechnology , electrolyte , chemistry , electron , electrode , electrochemistry , photocatalysis , physics , biochemistry , microstructure , quantum mechanics , metallurgy , catalysis
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.