Electrochemical ammonia synthesis from nitrite assisted by in situ generated hydrogen atoms on a nickel phosphide catalyst

Abstract

Investigating green and effective means for ammonia synthesis is an important but challenging task. Electrochemical ammonia synthesis (EAS) from an indirect route (N₂ → NO_x → NH₃) provides a feasible alternative strategy. The key step in this route is the reduction of NO_x to NH₃ instead of N₂, which requires the investigation of efficient catalysts with high selectivity of NH₃. Herein, we initially demonstrate a highly efficient electrochemical reduction of NO₂⁻ to NH₃ with nickel phosphide (Ni₂P) as the catalyst. The system exhibits low onset potential (0.2 V vs. RHE) and high faradaic efficiency (>90%) for EAS. Experimental results and theoretical calculations reveal that the in situ generated hydrogen atoms on the surface of Ni₂P greatly promote the reduction of NO₂⁻ to NH₃.