Grey hematite photoanodes decrease the onset potential in photoelectrochemical water oxidation

Peng-Fei Liu; Chongwu Wang; Yun Wang; Yuhang Li; Bo Zhang; Li-Rong Zheng; Zheng Jiang; Huijun Zhao; Hua-Gui Yang

doi:10.1016/j.scib.2021.02.016

Grey hematite photoanodes decrease the onset potential in photoelectrochemical water oxidation

Sci Bull (Beijing). 2021 May 30;66(10):1013-1021. doi: 10.1016/j.scib.2021.02.016. Epub 2021 Feb 9.

Authors

Peng-Fei Liu¹, Chongwu Wang¹, Yun Wang², Yuhang Li¹, Bo Zhang³, Li-Rong Zheng⁴, Zheng Jiang⁵, Huijun Zhao⁶, Hua-Gui Yang⁷

Affiliations

¹ Key Laboratory for Ultrafine Materials of Ministry of Education, Shanghai Engineering Research Center of Hierarchical Nanomaterials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China.
² Centre for Clean Environment and Energy, Griffith University, Gold Coast Campus, QLD 4222, Australia.
³ State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science and Laboratory of Advanced Materials, Fudan University, Shanghai 200438, China.
⁴ Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
⁵ Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China.
⁶ Centre for Clean Environment and Energy, Griffith University, Gold Coast Campus, QLD 4222, Australia. Electronic address: h.zhao@griffith.edu.au.
⁷ Key Laboratory for Ultrafine Materials of Ministry of Education, Shanghai Engineering Research Center of Hierarchical Nanomaterials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China. Electronic address: hgyang@ecust.edu.cn.

PMID: 36654246
DOI: 10.1016/j.scib.2021.02.016

Abstract

Photoelectrochemical (PEC) water splitting for solar energy conversion into chemical fuels has attracted intense research attention. The semiconductor hematite (α-Fe₂O₃), with its earth abundance, chemical stability, and efficient light harvesting, stands out as a promising photoanode material. Unfortunately, its electron affinity is too deep for overall water splitting, requiring additional bias. Interface engineering has been used to reduce the onset potential of hematite photoelectrode. Here we focus instead on energy band engineering hematite by shrinking the crystal lattice, and the water-splitting onset potential can be decreased from 1.14 to 0.61 V vs. the reversible hydrogen electrode. It is the lowest record reported for a pristine hematite photoanode without surface modification. X-ray absorption spectroscopy and magnetic properties suggest the redistribution of 3d electrons in the as-synthesized grey hematite electrode. Density function theory studies herein show that the smaller-lattice-constant hematite benefits from raised energy bands, which accounts for the reduced onset potential.

Keywords: Energy band; Hematite; Onset potential; Photoelectrochemical water oxidation; Spin states.