Electrochemical surface reconstruction of amorphous Co-based boride for nitrate reduction process.

The development of efficient catalysts for nitrate reduction to ammonia is crucial for sustainable nitrogen cycle management. In this study, we introduce an amorphous multimetal borides (CoFeNiB) catalyst that demonstrates exceptional performance in the electrochemical reduction of nitrate to ammonia. X-ray photoelectron spectroscopy (XPS) and in-situ Raman spectroscopy reveal that the catalyst exhibits a unique surface reconstruction during the reaction, leading to the formation of CoOOH, where Co ions can serve as active sites, significantly enhancing the adsorption of nitrate ions and atomic hydrogen, thereby promoting the reduction reaction. Specially, besides the activity enhancement of CoFeNiB compared with CoFeB and CoB, the stability of it can be markedly improved by the synergistic effect of Ni and Fe in the catalyst. Consequently, the CoFeNiB catalyst achieves a stable Faradaic efficiency above 90 % across a broad voltage range of 0 ∼ -0.6 V vs reversible hydrogen electrode (RHE) and an ammonia yield peaked of 3961.4 mmol g h at -0.6 V vs RHE. The CoFeNiB catalyst offers a promising avenue for the efficient and stable synthesis of ammonia from nitrate, addressing key challenges in environmental sustainability and nitrogen management.