High entropy borides as efficient catalysts for electrochemical reduction of nitrate to ammonia

Abstract

Electrochemical reduction of nitrate (NO3-RR) to ammonia has attracted great attention as a strategy for simultaneously achieving pollutant removal and economic product acquisition. To achieve high Faradaic efficiency of ammonia (FE) and ammonia selectivity, it is necessary to develop highly active catalysts with strong hydrogenation ability. In this work, we report high-entropy-borides (HEB) with tunable cation composition as high-performance catalysts for NO3-RR. Taking (TiVCrMo)B2 as the model material systems, we systematically investigate the effect of doping (Co, Fe, and Ni) on the activity of NO3-RR. Electrochemical test results show that the HEB doped with Co element exhibits the optimal performance, with a FE reaching 97.9 %. Combining several advanced spectroscopic techniques, we find that Co dopant can effectively facilitate the hydrogenation process of NO3-RR. This work demonstrates high-entropy ceramics as an excellent platform for rational design of highly active catalysts for energy and environmental applications.