Unlocking the Potential of Mn‐based Catalyst for Durable Two‐electron Oxygen Reduction in Acid at High Current Densities

Electrochemical synthesis of H2O2 by two‐electron oxygen reduction (2e− ORR) often shows limited stability at high current densities in acidic media. Mn‐based catalysts have been demonstrated highly stable for four‐electron ORR thanks to their intrinsically low rate constant for Fenton‐like reactions. However, their activity toward acidic 2e− ORR remains low because of too strong adsorption to *OOH. Here, we report a diatomic Mn catalyst with high‐spin MnII centers to enable high onset potential (0.69 V), high selectivity (> 90%) and outstanding stability (240 h under 300 mA cm−2) towards H2O2 electrosynthesis in acid. Theoretical calculations and in situ spectroscopies reveal that the diatomic Mn sites have downshifted d‐band center and thus weakened adsorption strength for *OOH. Moreover, the inertia of the MnII sites toward the troublesome Fenton‐like reactions leads to the long‐term stability at high current densities. We further demonstrate the functionalization of waste polyethylene (PE) using the high‐concentration H2O2 as produced, which provides a sustainable route toward on‐site upcycling of plastic waste.