Insight into the Catalytic Activity of Amorphous Multimetallic Catalysts under a Magnetic Field toward the Oxygen Evolution Reaction.

Slow kinetics in the oxygen evolution reaction (OER) remains a Gordian knot to develop an efficient and cost-effective electrocatalyst in electrochemical water splitting. In recent studies, either a synergistic effect on multimetallic catalysts or spin polarization in ferromagnetic materials is considered as a desirable way to improve water electrolysis. Herein, the OER performance of amorphous FeNiCo-based multimetallic catalysts with adjustable composition was investigated from the perspective of atomic structure. Mössbauer spectra results demonstrate that the OER activities exhibit a significant dependence on the local structure of catalysts in which a catalyst with a high content of Fe clusters of low coordination numbers tends to obtain higher activity. Furthermore, benefiting from the spin polarization of these ferromagnetic catalysts, the OER activity is notably enhanced in the presence of a magnetic field. In particular, overpotential reduction exceeding 20 mV (above 100 mA cm-2) in alkaline OER performance is observed for strong ferromagnetic catalysts in comparison with the weak ferromagnetic ones. An increment of 65.2% in turnover frequency is achieved for the catalyst with the strongest ferromagnetism. This magnetic enhancement strategy affords an effective way of improving the water oxidation performance on amorphous ferromagnetic catalysts.