pH-induced hydrothermal synthesis of Bi2WO6 nanoplates with controlled crystal facets for switching bifunctional photocatalytic water oxidation/reduction activity

Li Wang; Changfa Guo; Fang Chen; Jiqiang Ning; Yijun Zhong; Yong Hu

doi:10.1016/j.jcis.2021.06.044

pH-induced hydrothermal synthesis of Bi₂WO₆ nanoplates with controlled crystal facets for switching bifunctional photocatalytic water oxidation/reduction activity

J Colloid Interface Sci. 2021 Nov 15:602:868-879. doi: 10.1016/j.jcis.2021.06.044. Epub 2021 Jun 10.

Authors

Li Wang¹, Changfa Guo², Fang Chen³, Jiqiang Ning⁴, Yijun Zhong¹, Yong Hu⁵

Affiliations

¹ Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Department of Chemistry, Zhejiang Normal University, Jinhua 321004, China.
² Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Department of Chemistry, Zhejiang Normal University, Jinhua 321004, China. Electronic address: changfa.guo@zjun.edu.cn.
³ Hangzhou Institute of Advanced Studies, Zhejiang Normal University, Hangzhou 311231, China.
⁴ Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China.
⁵ Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Department of Chemistry, Zhejiang Normal University, Jinhua 321004, China; Hangzhou Institute of Advanced Studies, Zhejiang Normal University, Hangzhou 311231, China. Electronic address: yonghu@zjnu.edu.cn.

PMID: 34175635
DOI: 10.1016/j.jcis.2021.06.044

Abstract

Bifunctional photocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have attracted growing interest to understand the mechanisms governing different evolution reactions, and the bifunctional activity of a single type of crystalline photocatalyst has gained especial attention. We herein report the high photocatalytic OER and HER activities of Bi₂WO₆ nanoplates (BWO NPs) which are synthesized by a simple hydrothermal method, and the switchable OER and HER performances controlled by the pH value of the precursor solvent. In the pH range from 4 to 9, the thickness of BWO NPs along the [001] direction exhibits interesting dependence on the pH value, which decreases as the pH value increases. Correspondingly, the BWO NPs obtained at the pH value of 7 (BWO-7) show the highest photocatalytic OER activity, while the BWO NPs synthesized at the pH value of 9 (BWO-9) exhibit the highest photoactivity towards HER. The electronic band structure analysis indicates that the highest photocatalytic OER activity is related to the band alignment of the valence band maximum of Bi₂WO₆, which determines the efficient separation of photogenerated electrons and holes as well as the fast charge transfer kinetics. The crystal facet evolution resulting from thickness reduction promotes the exposure of {001} facets for HER and decreases the exposure of {100} and {010} facets for OER. This work provides new insights into the combined effects of crystal facets and electronic band structures on photocatalysis.

Keywords: Band structure; Bi(2)WO(6); Crystal facet engineering; Photocatalytic H(2) production; Photocatalytic O(2) evolution.