Breaking scaling relations in nitrogen reduction with asymmetrical heterobimetallic FeCo sites to boost ammonia synthesis

Abstract

The electrochemical nitrogen reduction reaction (NRR) driven by renewable electricity is an up-and-coming method for sustainable ammonia production. However, since it is a multi-intermediate reaction, the inherent scaling relations between the adsorption energies of intermediates place restrictions on the overall performance. Herein, asymmetrical heterobimetallic sites are proposed to break the restriction of scaling relations on catalytic activity and boost ambient ammonia synthesis. According to density functional theory calculations, the heteronuclear FeCo dimer sites featuring a polarized surface with multielectron sites enable weakening of the NN bond and maximized activation of N₂. The optimization of the binding strength of certain intermediates thus becomes feasible, contributing to a significantly reduced energy barrier of the NRR. Experimentally, the asymmetrical heterobimetallic catalyst delivers a superior ammonia yield rate of 70.11 μg h⁻¹ mg⁻¹ with a corresponding Faradaic efficiency of 32.16%. This study suggests that the presence of asymmetrical heterobimetallic sites defines a special opportunity for breaking scaling relations to achieve efficient multi-intermediate electrocatalytic reactions.