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

Abstract

AbstractManganese oxides (MnOx) are promising candidates for water oxidation catalysts. However, the true active centers remain elusive due to the dynamic nature of MnOx 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 MnOx electrocatalysts. Electrochemical results indicate that the defective cubical tri‐manganese complex is a robust molecular catalyst to facilitate 4e− water oxidation to produce O2 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 MnOx systems. In contrast, the di‐manganese complex exhibits marginal catalytic activity. This work provides molecular insights into the true active centers of MnOx and aids in the precise design of more efficient MnOx water oxidation electrocatalysts.