Carbon Nanocage Confining CuCo Bimetallic Interface with Low Nitrate Adsorption Energy for Highly Efficient Electrochemical Ammonia Synthesis

This work aimed to improve the Faraday efficiency and formation rate of ammonia with a low reaction potential in the electroreduction of nitrate. For this purpose, CuCo bimetallic interface-rich catalysts confined in porous nitrogen-doped carbon nanocages (CuCo/NC) were designed. Results of in situ Fourier transform infrared spectroscopy suggested that the reaction path followed the sequence NO3- -> *NO3 -> *NO2 -> *NO -> *NOH -> *NH2OH -> *NH3 -> NH3. Density functional theory calculations revealed that the adsorption of nitrate over the CuCo bimetallic interface was thermodynamically favorable. CuCo bimetallic interface changed the rate-determining step of nitrate reduction at Cu sites from nitrate adsorption to *NO hydrogenation and promoted the continuous hydrogenation of nitrogen-related intermediates. Over the CuCo/NC catalyst, Faraday efficiency and formation rate of ammonia were 95.1% (at -0.59 V vs reversible hydrogen electrode (RHE)) and 9110.8 mu g h(-1) mg(cat.)(-1) (at -0.79 V vs RHE), which were higher than those over Cu/NC and Co/NC catalysts.