Covalency competition dominates the water oxidation structure-activity relationship on spinel oxides

• Main Authors: Sun, Yuanmiao, Liao, Hanbin, Wang, Jiarui, Chen, Bo, Sun, Shengnan, Ong, Samuel Jun Hoong, Xi, Shibo, Diao, Caozheng, Du, Yonghua, Wang, Jia-Ou, Breese, Mark B. H., Li, Shuzhou, Zhang, Hua, Xu, Jason Zhichuan
• Other Authors: School of Materials Science and Engineering
• Format: Article
• Language: English
• Published: 2021
• Subjects: Engineering::Materials; Electrocatalysis; Water Oxidation; Spinel Oxides; Covalency Competition
• Online Access: https://hdl.handle.net/10356/148451
• Institution: Nanyang Technological University

Spinel oxides have attracted growing interest over the years for catalysing the oxygen evolution reaction (OER) due to their efficiency and cost-effectiveness, but fundamental understanding of their structure–property relationships remains elusive. Here we demonstrate that the OER activity on spinel oxides is intrinsically dominated by the covalency competition between tetrahedral and octahedral sites. The competition fabricates an asymmetric MT−O−MO backbone where the bond with weaker metal–oxygen covalency determines the exposure of cation sites and therefore the activity. Driven by this finding, a dataset with more than 300 spinel oxides is computed and used to train a machine-learning model for screening the covalency competition in spinel oxides, with a mean absolute error of 0.05 eV. [Mn]T[Al0.5Mn1.5]OO4 is predicted to be a highly active OER catalyst and subsequent experimental results confirm its superior activity. This work sets mechanistic principles of spinel oxides for water oxidation, which may be extendable to other applications.