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

doi:10.1002/anie.202217026

Subsurface Engineering Induced Fermi Level De-pinning in Metal Oxide Semiconductors for Photoelectrochemical Water Splitting

Angew Chem Int Ed Engl. 2023 Feb 20;62(9):e202217026. doi: 10.1002/anie.202217026. Epub 2023 Jan 24.

Authors

Jun Wang^{1

2}, Ganghai Ni², Wanru Liao², Kang Liu², Jiawei Chen¹, Fangyang Liu¹, Zongliang Zhang¹, Ming Jia¹, Jie Li¹, Junwei Fu², Evangelina Pensa³, Liangxing Jiang^{1

4}, Zhenfeng Bian⁵, Emiliano Cortés³, Min Liu²

Affiliations

¹ School of Metallurgy and Environment, Central South University, Changsha, 410083, Hunan, P.R. China.
² Hunan Joint International Research Center for Carbon Dioxide Resource Utilization, State Key Laboratory of Powder Metallurgy, School of Physics and Electronics, Central South University, Changsha, 410083, Hunan, P.R. China.
³ Nanoinstitut München, Fakultät für Physik, Ludwig-Maximilians-Universität München, 80539, München, Germany.
⁴ Hunan Provincial Key Laboratory of Nonferrous Value-added Metallurgy, Changsha, 410083, Hunan, P.R. China.
⁵ MOE Key Laboratory of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, Shanghai Normal University, Shanghai, 200234, P.R. China.

PMID: 36577697
DOI: 10.1002/anie.202217026

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 BiVO₄ , Bi₂ O₃ , TiO₂ with outstanding stability for 72 h, outperforming most reported works under the identical conditions.

Keywords: Fermi Level De-Pinning; Open Circuit Photovoltage; Photoelectrochemical Water Splitting; Promoted Charge Transfer; Subsurface Engineering.

Grants and funding

802989/European Commission