A Bi-Co Corridor Construction Effectively Improving the Selectivity of Electrocatalytic Nitrate Reduction toward Ammonia by Nearly 100%

Improving the selective ammonia production capacity of electrocatalytic nitrate reduction reaction (NO3RR) at ambient conditions is critical to the future development and industrial application of electrosynthesis of ammonia. However, the reaction involves multi-proton and electron transfer as well as the desorption and underutilization of intermediates, posing a challenge to the selectivity of NO3RR. Here the electrodeposition site of Co is modulated by depositing Bi at the bottom of the catalyst, thus obtaining the Co+Bi@Cu NW catalyst with a Bi-Co corridor structure. In 50 mm NO3-, Co+Bi@Cu NW exhibits a highest Faraday efficiency of approximate to 100% (99.51%), an ammonia yield rate of 1858.2 mu g h-1 cm-2 and high repeatability at -0.6 V versus the reversible hydrogen electrode. Moreover, the change of NO2- concentration on the catalyst surface observed by in situ reflection absorption imaging and the intermediates of the NO3RR process detected by electrochemical in situ Raman spectroscopy together verify the NO2- trapping effect of the Bi-Co corridor structure. It is believed that the measure of modulating the deposition site of Co by loading Bi element is an easy-to-implement general method for improving the selectivity of NH3 production as well as the corresponding scientific research and applications. A Bi-Co corridor-like structure is designed by exploiting the limited electron accessibility of Bi element to deposit Co to the bottom of the catalyst. During the electrocatalytic reaction, NO3- is preferentially adsorbed on the Co site , and part of the escaped intermediate NO2- will be captured and converted into NH3 by the outer Bi, thus improving the Faraday efficiency.image

Automated summary

This study demonstrates the improvement of selective ammonia production capacity in the electrocatalytic nitrate reduction reaction (NO3RR) by modulating the electrodeposition site of Co. The designed Bi-Co corridor catalyst exhibits high Faraday efficiency, ammonia yield rate, and repeatability, and the trapping effect of NO2- by the Bi-Co corridor structure is verified.