Subsurface Engineering Induced Fermi Level De‐pinning in Metal Oxide Semiconductors for Photoelectrochemical Water Splitting
Jun Wang, Ganghai Ni, Wanru Liao, Kang Liu, Jiawei Chen, Fangyang Liu, Zongliang Zhang, Ming Jia, Jie Li, Junwei Fu, Evangelina Pensa, Liangxing Jiang, Zhenfeng Bian, Emiliano Cortés, Min Liu
Abstract
Abstract Photoelectrochemical (PEC) water splitting is a promising approach for renewable solar light conversion. However, surface Fermi level pinning (FLP), caused by surface trap states, severely restricts the PEC activities. Theoretical calculations indicate subsurface oxygen vacancy (sub‐O v ) could release the FLP and retain the active structure. A series of metal oxide semiconductors with sub‐O v were prepared through precisely regulated spin‐coating and calcination. Etching X‐ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), and electron energy loss spectra (EELS) demonstrated O v located at sub ∼2–5 nm region. Mott–Schottky and open circuit photovoltage results confirmed the surface trap states elimination and Fermi level de‐pinning. Thus, superior PEC performances of 5.1, 3.4, and 2.1 mA cm −2 at 1.23 V vs. RHE were achieved on BiVO 4 , Bi 2 O 3 , TiO 2 with outstanding stability for 72 h, outperforming most reported works under the identical conditions.