The electrochemical nitrate reduction reaction (NitRR) affords a sustainable way for nitrate mitigation and ammonia synthesis, but there are still some problems such as poor nitrate conversion, low ammonia selectivity, and slow reaction kinetics. A clear structure-performance relationship is essential for designing efficient catalysts and understanding the reaction mechanisms. Herein, ultrathin nickel metal–organic framework (Ni-MOF) nanosheets supported on Ni foam featuring a well-defined stable structure, large electrochemically active surface area, and low electron transport resistance were prepared by a one-step solvothermal process. At −1.4 V, the nitrate reduction, rate constant, ammonia selectivity, and yield reached 96.4%, 0.448 h⁻¹, 80%, and 110.13 ug·h⁻¹·cm⁻², respectively. Experimental and theoretical studies demonstrated that the hydroxyl-ligated Ni atoms exhibited higher nitrate adsorption properties and lower activation energy towards NitRR compared to carboxylic acid-ligated Ni atoms. Mechanism investigations revealed a nitrate-to-ammonia reaction pathway involving multiple intermediate species on Ni-MOF nanosheet catalysts. This work offers a new avenue to construct highly efficient electrocatalysts for the selective transformation of nitrate to valuable ammonia.

电化学硝酸盐还原反应（NitRR）为硝酸盐减排和氨合成提供了一种可持续的途径，但仍存在硝酸盐转化率低、氨选择性低和反应动力学慢等问题。清晰的结构-性能关系对于设计高效催化剂和理解反应机理至关重要。在此，通过一步溶剂热法制备了负载在泡沫镍上的超薄镍金属-有机骨架 (Ni-MOF) 纳米片，该纳米片具有明确的稳定结构、大的电化学活性表面积和低电子传输阻力。在-1.4 V 时，硝酸盐还原率、速率常数、氨选择性和产率分别达到96.4%、0.448 h ^-1、80% 和110.13 ug·h ^-1 ·cm ^-2， 分别。实验和理论研究表明，与羧酸连接的镍原子相比，羟基连接的镍原子对 NitRR 表现出更高的硝酸盐吸附性能和更低的活化能。机理研究揭示了硝酸盐到氨的反应途径，涉及 Ni-MOF 纳米片催化剂上的多种中间体。这项工作为构建用于将硝酸盐选择性转化为有价值的氨的高效电催化剂提供了一条新途径。