Distorted spinel ferrite heterostructure triggered by alkaline earth metal substitution facilitates nitrogen localization and electrocatalytic reduction to ammonia

Abstract

Electrocatalytic nitrogen reduction reaction (NRR) is a promising strategy for green synthesis of ammonia. However, current system still suffers from weak reagent supply and high reaction barrier, and modulating the structural/electronic configurations of electrocatalysts with optimized properties plays a vital role for achieving efficient NRR. Herein, distorted spinel ferrite heterostructure is rationally designed via large-scale substitution of alkaline earth metal with large atomic radius, and serves as a highly active and selective NRR electrocatalyst. The distorted structure generates superior N2 affinity to realize its localization, which is beneficial for the following adsorption. Moreover, the number of electrons occupied at the Fermi level of active sites is greatly increased, so that the electron transfer to the adsorbed N2 is efficiently facilitated and the reaction barrier is significantly reduced. Such optimized electronic structure also dramatically increases the reaction barrier of hydrogen evolution reaction (HER), allowing H+ to preferentially participate in the nitrogen hydrogenation. With boosted NRR and suppressed HER, an outstanding NRR performance with a superior Faradaic efficiency of 76.7 % and a high NH3 yield rate of 36.4 μg h−1 mg−1 is achieved under ambient conditions. This work offers valuable insights into the rational design of spinel ferrite for efficient electrocatalysis.