Spin unlocking oxygen evolution reaction on antiperovskite nitrides

Abstract

An efficient and low-cost oxygen evolution reaction (OER) electrocatalyst is key for electrochemical energy conversion and storage technologies. However, there is a lack of a strategy to guide the development of cost-effective antiperovskite nitrides with composition-sensitive function adjustability. Herein, we triggered the low-spin to high-spin transition of Fe³⁺ in Cu_0.5NFe_3.5 by partially doping Ni at the Fe sites, enabling Cu_0.5NFe₃Ni_0.5 to significantly accelerate the oxidation of the in situ electrochemically formed amorphous FeNi (oxy)hydroxide redox couple, an initial water oxidation step, as well as subsequent water oxidation. Theoretical calculations indicated that the high-spin Fe³⁺ induces the formation of a paramagnetic FeNi (oxy)hydroxide catalytic layer on the ferromagnetic Cu_0.5NFe₃Ni_0.5 core to accelerate the OER kinetics, thus Cu_0.5NFe₃Ni_0.5 displays an overpotential of 244 mV at 10 mA cm⁻² as an outstanding OER electrocatalyst, outperforming the benchmark IrO₂ catalyst. Our findings are expected to unlock the potential of designing ideal antiperovskite-based electrocatalysts with adjustable spin states for use in the energy conversion and storage fields.