Edge-Sharing Octahedrally Coordinated NiFe Dual Active Sites on ZnFe2 O4 for Photoelectrochemical Water Oxidation

Zhiyong Jiang; Xiaodi Zhu; Zhiyu Wang; Wei Liu; Wensheng Yan; Kevin Sivula; Jun Bao

doi:10.1002/advs.202301869

Edge-Sharing Octahedrally Coordinated NiFe Dual Active Sites on ZnFe₂ O₄ for Photoelectrochemical Water Oxidation

Adv Sci (Weinh). 2023 Aug;10(22):e2301869. doi: 10.1002/advs.202301869. Epub 2023 Jun 1.

Authors

Zhiyong Jiang¹, Xiaodi Zhu¹, Zhiyu Wang¹, Wei Liu², Wensheng Yan¹, Kevin Sivula³, Jun Bao^{1

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Affiliations

¹ National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, China.
² State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, China.
³ Laboratory for Molecular Engineering of Optoelectronic Nanomaterials (LIMNO), École Polytechnique Fédérale de Lausanne, Station 6, Lausanne, 1015, Switzerland.
⁴ Key Laboratory of Precision and Intelligent Chemistry, University of Science and Technology of China, Hefei, Anhui, 230026, China.
⁵ iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Hefei, Anhui, 230029, China.

Abstract

The structural properties of octahedral sites (B_Oh ) in spinel oxides (AB₂ O₄ ) play vital roles in the electrochemical performance of oxygen-related reactions. However, the precise manipulation of AB₂ O₄ remains challenging due to the complexity of their crystal structure. Here, a simple and versatile molten-salt-mediated strategy is reported to introduce Ni²⁺ in B_oh sites intentionally on the surface of zinc ferrite (ZnFe₂ O₄ , ZFO) to promote the active sites for photoelectrochemical (PEC) water splitting. The as-created photoanode (ZFO-MSNi) shows a remarkable cathodic shift of ≈ 450 mV (turn-on voltage of ≈ 0.6 V_RHE ) as well as three times the 1-sun photocurrent density at 1.23 V_RHE for PEC water oxidation in comparison with bare ZFO. A comprehensive structural characterization clearly reveals the local structure of the introduced Ni²⁺ in ZFO-MSNi. Fewer surface trapping states are observed while the precisely introduced Ni²⁺ and associated neighboring Fe^(3-σ)+ (0<σ<1) sites unite in an edge-sharing octahedral configuration to function as NiFe dual active sites for PEC water oxidation. Moreover, open circuit potential measurements and rapid-scan voltammetry investigation give further insight into the enhanced PEC performance. Overall, this work displays a versatile strategy to regulate the surface active sites of photoelectrodes for increasing performance in PEC solar energy conversion systems.

Keywords: dual active sites; molten salt; spinel ferrites; ultra-low onset potential; water splitting.

Abstract

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