Spin-Enhanced O-H Cleavage in Electrochemical Water Oxidation.

Herein we report the vital role of spin polarization in proton-transfer-mediated water oxidation over a magnetized catalyst. During the electrochemical oxygen evolution reaction (OER) over ferrimagnetic Fe3 O4 , the external magnetic field induced a remarkable increase in the OER current, however, this increment achieved in weakly alkaline pH (pH 9) was almost 20 times that under strongly alkaline conditions (pH 14). The results of the surface modification experiment and H/D kinetic isotope effect investigation confirm that, at weakly alkaline pH, during the nucleophilic attack of FeIV =O by molecular water, the magnetized Fe3 O4 catalyst polarizes the spin states of the nucleophilic attacking intermediates. The spin-enhanced singlet O-H cleavage and triplet O-O bonding occur synergistically, which promotes the O2 generation more significantly than the strongly alkaline case involving only spin-enhanced O-O bonding.