Electrocatalytic water oxidation with manganese phosphates

• Published in: Nature communications Vol. 15; no. 1; p. 1410
• Main Authors: Yang, Shujiao, Yue, Kaihang, Liu, Xiaohan, Li, Sisi, Zheng, Haoquan, Yan, Ya, Cao, Rui, Zhang, Wei
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15.02.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 140/133; 140/146; 140/58; 147/135; 147/143; 147/3; 639/638/161/886; 639/638/77/886; Bonding; Catalysts; Coordination; Electrocatalysts; Homology; Humanities and Social Sciences; Manganese; multidisciplinary; Oxidation; Phosphates; Reaction mechanisms; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-45705-1

As inspired by the Mn 4 CaO 5 oxygen evolution center in nature, Mn-based electrocatalysts have received overwhelming attention for water oxidation. However, the understanding of the detailed reaction mechanism has been a long-standing problem. Herein, homologous KMnPO 4 and KMnPO 4 •H 2 O with 4-coordinated and 6-coordinated Mn centers, respectively, are prepared. The two catalysts constitute an ideal platform to study the structure-performance correlation. The presence of Mn(III), Mn(IV), and Mn(V) intermediate species are identified during water oxidation. The Mn(V)=O species is demonstrated to be the substance for O−O bond formation. In KMnPO 4 •H 2 O, the Mn coordination structure did not change significantly during water oxidation. In KMnPO 4 , the Mn coordination structure changed from 4-coordinated [MnO 4 ] to 5-coordinated [MnO 5 ] motif, which displays a triangular biconical configuration. The structure flexibility of [MnO 5 ] is thermodynamically favored in retaining Mn(III)−OH and generating Mn(V)=O. The Mn(V)=O species is at equilibrium with Mn(IV)=O, the concentration of which determines the intrinsic activity of water oxidation. This study provides a clear picture of water oxidation mechanism on Mn-based systems. Understanding water oxidation on Mn-based catalysts remains a long-standing challenge. Here, the authors use homologous KMnPO 4 and KMnPO 4 •H 2 O as model catalyst to show that Mn(V)=O is responsible for O−O bond formation and its concentration determines the intrinsic activity.