Revealing and modulating catalyst reconstruction for highly efficient electrosynthesis of ammonia.

Electrocatalytic nitrate reduction (NORR) is a promising route for sustainable ammonia synthesis under mild conditions. The widely studied Co-based catalysts undergo significant reconstruction due to nitrate oxidation and electric-field reduction during NORR, leading to activity degradation. To address this issue, we develop a CoNi heterostructured catalyst that consists of interlaced metallic Co and Ni domains. Operando X-ray absorption spectroscopy and other in-situ characterization techniques, in conjunction with theoretical calculations, demonstrate that Ni domains function as electron reservoir, which transfer electrons to Co and prevent the accumulation of high-valence Co. Besides, the abundant Co/Ni interfaces also facilitate the NORR process, thereby achieving a NH Faraday efficiency of 99.21%, a NH yield rate of 93.55 mg h cm, and a NORR stability of 120 h. Our analyses delve into the underlying causes of the observed stability of metallic Co in CoNi and provide compelling evidence that the discrepancy between the adsorption quantity of NO on catalyst surface and the corresponding electron supply is a pivotal factor influencing the reconstruction process.