Energy-Efficient Ammonia Synthesis from Nitrate via CoNi Alloys Incorporated in Carbon Frameworks

As a nitrogen-containing source, nitrate is regarded as a promising precursor for generating ammonia (NH 3 ) through electrochemical processes that can potentially mitigate the problem of groundwater contamination and the hydrogen-carrier energy crisis. Herein, we report a cobalt zeolitic imidazolate framework (ZIF-67)-derived catalyst of CoNi alloys incorporated in N-doped carbon frameworks for nitrate electroreduction. Computational results obtained using the density functional theory give a deep insight that the structure of CoNi alloys embedded in the N-doped carbon skeleton can inhibit the production of hydrogen and facilitate the hydrogenation of *NO intermediates. The enriched active sites from the ZIF-67-derived structure and the introduction of Ni in the catalyst afford desirable electrocatalytic performance. Finally, the optimized CoNi@NC hybrid can achieve an ammonia production of 168 mmol g cat –1 h –1 and a Faradaic efficiency of ∼93% at a potential as low as −0.1 V vs reversible hydrogen electrode (RHE). The highest yield rate of 1254 mmol g cat –1 h –1 can be detected at −0.6 V vs RHE. This study can inspire further development of non-noble metal-based hybrid electrocatalysts for nitrate reduction and also anticipation into sustainable synthesis of carbon-related fuels from CO 2 reduction.