Electrochemical ammonia synthesis from nitrite assisted by <i>in situ</i> generated hydrogen atoms on a nickel phosphide catalyst
Xiao Yang, Lei Kang, Chuanjun Wang, Fulai Liu, Yong Chen
Abstract
Investigating green and effective means for ammonia synthesis is an important but challenging task. Electrochemical ammonia synthesis (EAS) from an indirect route (N2 → NOx → NH3) provides a feasible alternative strategy. The key step in this route is the reduction of NOx 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.