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

As a nitrogen-containing source, nitrate is regardedas a promisingprecursor for generating ammonia (NH3) through electrochemicalprocesses that can potentially mitigate the problem of groundwatercontamination and the hydrogen-carrier energy crisis. Herein, we reporta cobalt zeolitic imidazolate framework (ZIF-67)-derived catalystof CoNi alloys incorporated in N-doped carbon frameworks for nitrateelectroreduction. Computational results obtained using the densityfunctional theory give a deep insight that the structure of CoNi alloysembedded in the N-doped carbon skeleton can inhibit the productionof hydrogen and facilitate the hydrogenation of *NO intermediates.The enriched active sites from the ZIF-67-derived structure and theintroduction of Ni in the catalyst afford desirable electrocatalyticperformance. Finally, the optimized CoNi@NC hybrid can achieve anammonia production of 168 mmol g(cat) (-1) h(-1) and a Faradaic efficiency of similar to 93% ata 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. Thisstudy can inspire further development of non-noble metal-based hybridelectrocatalysts for nitrate reduction and also anticipation intosustainable synthesis of carbon-related fuels from CO2 reduction. A hybrid structure of CoNi@NC with enrichedactive sitesand optimized electronic structure is synthesized for energy efficientlycatalyzing nitrate to ammonia.