Electrochemical Ammonia Synthesis from Nitrite Assisted by In-Situ Generated Hydrogen Atoms on Nickel Phosphide Catalyst

Abstract

Exploring green and effective means for ammonia synthesis is an important but challenging task. Electrochemical ammonia synthesis (EAS) from 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 exploration of efficient catalysts with high NH3 selectivity. Herein, we initially demonstrate 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 faradic efficiency (>90%) for EAS. Experimental results and theoretical calculations reveal that in-situ generated hydrogen atoms on Ni2 P surface greatly promote the reduction of NO2 - to NH3. This work sheds important light on metal phosphides catalyzed EAS through nitrite reduction and will inspire further interest on ammonia synthesis.