Optimizing d-p orbital hybridization by tuning high-entropy spinel oxides for enhanced alkaline OER efficiency

Dongyuan Song, Xueda Liu, Yingkai Wu, Quan Quan, Yuta Tsuji, Xiaoge Liu, Hikaru Saito, Shiro Ihara, Liyuan Dai, Xiaoguang Liang, Takeshi Yanagida, Johnny C. Ho*, SenPo Yip*

*Corresponding author for this work

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

Abstract

The growing need for cost-effective and efficient energy conversion technologies drives the development of advanced catalysts for the oxygen evolution reaction (OER). Our research focuses on high-entropy spinel oxides (HESOs) as efficient OER electrocatalysts. Using the molten salt synthesis (MSS) method, we prepared HESO nanoparticles from Fe, Ni, Co, Mn, and Zn. By adjusting the precursor ratios, we obtained equimolar (Ni0.2Fe0.2Co0.2Mn0.2Zn0.2)3O4, CoMn-rich, and NiFe-rich samples to examine compositional effects. Among these, the CoMn-rich HESO sample exhibited superior catalytic performance in 1 M KOH solution, with an overpotential of 330.1 mV at 10 mA cm−2 and a Tafel slope of 53.5 mV dec−1. Its promising long-term stability and enhanced reaction kinetics are significant. The synergistic effect of Co and Mn with high valence states and enhanced oxygen adsorption on the CoMn-rich HESO lower the energy barrier and accelerate electron transfer, improving the reaction kinetics. Density functional theory (DFT) calculations further reveal the relationship between orbital hybridization and catalytic performance, emphasizing the contribution of high valence metal active centers in improving performance. The density of states (DOS) analysis further demonstrates the stronger covalency between the 3d orbitals of the metal active site and the O 2p orbitals on the surface of CoMn-rich samples, which favors the absorption of oxygen species and thus improves the electrochemical performance. This work presents an effective method for HESO synthesis and opens new avenues for energy conversion research. © 2025 The Royal Society of Chemistry.
Original languageEnglish
Pages (from-to)13295-13304
JournalJournal of Materials Chemistry A
Volume13
Issue number18
Online published25 Mar 2025
DOIs
Publication statusPublished - 14 May 2025

Funding

This work was funded by the \u201CNetwork Joint Research Center for Materials and Devices\u201D of the Ministry of Education, Culture, Sports, Science and Technology (MEXT). The first author was supported by the China Scholarship Council (CSC). Y. T. is grateful to JSPS KAKENHI Grant Numbers JP21K04996 and JP22H05146 (Grant-in-Aid for Transformative Research Areas (A) \u201CSupra-ceramics\u201D) and the computer facilities provided by the Research Institute for Information Technology, Kyushu University, at the Supercomputer Center, the Institute for Solid State Physics, the University of Tokyo, and at Cyberscience Center, Tohoku University.

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