Molecular Insights into Active Sites of Manganese Oxide Based Water Oxidation Eletrocatalysts

Abstract Manganese oxides (MnO x ) are promising candidates for water oxidation catalysts. However, the true active centers remain elusive due to the dynamic nature of MnO x during electrolysis and/or activation, hindering progress in catalyst design and optimization. Herein, we aim to address such a challenge by preparing a defective cubical tri‐manganese complex and a di‐manganese complex to mimic the in‐plane and on‐edge subunits of birnessite‐like heterogeneous MnO x electrocatalysts. Electrochemical results indicate that the defective cubical tri‐manganese complex is a robust molecular catalyst to facilitate 4e − water oxidation to produce O 2 with an optimal Faradic efficiency of 95% and an average rate of oxygen generation of 46.4 µmol h cm −2 , which is among the highest values of reported manganese‐based molecular catalysts and is comparable with representative heterogeneous MnO x systems. In contrast, the di‐manganese complex exhibits marginal catalytic activity. This work provides molecular insights into the true active centers of MnO x and aids in the precise design of more efficient MnO x water oxidation electrocatalysts.