Fe-2 Dimers for Non-Polar Diatomic O-2 Electroreduction

Non-polar diatomic molecule activation is of great significance for catalysis. Despite the high atomic efficiency, the catalytic performance of single-atom catalysts is limited by insufficient receiving sites for diatomic molecule adsorption. Here, Fe-2 dimers were successfully synthesized through precisely regulating the metal loading on metal-organic frameworks. The unique role of metal dimers in activating diatomic O-2 molecules was explored. In alkaline electrolytes, the specific oxygen reduction reaction activity of Fe-2 dimers was 7 times higher than that of Fe-1 counterparts. The hydrogen atom transfer probes indicated a different activation mode for O-2 on Fe-1 and Fe-2 dimers, respectively. Theoretical calculation results revealed that Fe-2 dimers opened up a new reaction pathway by promoting the direct breaking of O=O bonds, thus avoiding the usual formation of *OOH intermediates, which helped explain the lower H2O2 yield and higher specific activity.