Interface Engineering of NiO/CuO Heterojunction Enabling Built-In Electric Field for Efficient Electrocatalytic Ammonia Oxidation Reaction

Electrocatalytic ammonia oxidation reaction (AOR), as a promising energy conversion technology, also offers ideas for the synthesis of high-value nitrogenous compounds such as nitrites and nitrates. However, the sluggish kinetics of AOR at the anode leads to high overpotential and elevated energy consumption, necessitating advanced catalysts. Here, we engineer a NiO/CuO heterojunction on a copper mesh (NiO/CuO@Cu), which generates a robust internal electric field at the NiO–CuO interface. The built-in electric field facilitates interface electron redistribution and surface electronic state modulation, significantly enhancing the charge transfer and AOR kinetics. The NiO/CuO@Cu catalyst exhibits a low onset potential of 1.38 V vs RHE, along with 95.8% ammonia conversion efficiency and 90.6% nitrite selectivity during 8-h operation at 1.6 V vs RHE. Notably, the catalyst shows excellent operation stability for over 56 h. This work presents interface engineering through heterojunction design as an effective strategy for AOR enhancement, providing valuable insights for developing high-performance electrocatalysts in energy conversion technologies.