The Self-Passivation Mechanism in Degradation of BiVO4 Photoanode

Xin Yao; Xin Zhao; Jun Hu; Huiqing Xie; Danping Wang; Xun Cao; Zheng Zhang; Yizhong Huang; Zhong Chen; Thirumany Sritharan

doi:10.1016/j.isci.2019.08.037

The Self-Passivation Mechanism in Degradation of BiVO₄ Photoanode

iScience. 2019 Sep 27:19:976-985. doi: 10.1016/j.isci.2019.08.037. Epub 2019 Aug 27.

Authors

Xin Yao¹, Xin Zhao², Jun Hu², Huiqing Xie³, Danping Wang¹, Xun Cao², Zheng Zhang³, Yizhong Huang², Zhong Chen⁴, Thirumany Sritharan⁵

Affiliations

¹ School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Singapore-Berkeley Research Initiative for Sustainable Energy (SinBeRISE) CREATE Tower, 1 Create Way, #11-00, Singapore 138602, Singapore.
² School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
³ Institute of Materials Research and Engineering, 2 Fusionopolis Way, Singapore 138634, Singapore.
⁴ School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Singapore-Berkeley Research Initiative for Sustainable Energy (SinBeRISE) CREATE Tower, 1 Create Way, #11-00, Singapore 138602, Singapore. Electronic address: ASZChen@ntu.edu.sg.
⁵ School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Singapore-Berkeley Research Initiative for Sustainable Energy (SinBeRISE) CREATE Tower, 1 Create Way, #11-00, Singapore 138602, Singapore. Electronic address: assritharan@ntu.edu.sg.

Abstract

BiVO₄ is a promising photoanode material for solar-assisted water splitting in a photoelectrochemical cell but has a propensity to degrade. Investigations carried out here in 0.1 M Na₂SO₄ electrolyte showed that degradation is by dissolution of V in the electrolyte while Bi is retained on the anode probably in the form of solid Bi oxide (Bi₂O₃, Bi₄O₇). Accumulation of Bi oxide on the anode surface leads to passivation from further degradation. Thermodynamic modeling of possible degradation reactions has provided theoretical support to this mechanism. This self-passivation is accompanied by a decrease in photocurrent density, but it protects the anode against extensive photocorrosion and contributes to long-term stability. This is a more definitive understanding of degradation of BiVO₄ during water splitting in a photoelectrochemical cell. This understanding is imperative for both fundamental and applied research.

Keywords: Chemical Reactions in Materials Science; Electrochemical Energy Conversion; Electrochemical Energy Storage; Materials Characterization.