Enhanced Electrochemical Reduction of N-2 to Ammonia over Pyrite FeS2 with Excellent Selectivity

Electrochemical reduction of N-2 reaction (NRR) into NH3 promises a sustainable and environmentally friendly technology at ambient temperature. However, high energy barrier and the competition with the hydrogen evolution reaction result in poor NH3 yield and low faradaic efficiency (FE) of NRR. Herein, the FeS2 catalyst was synthesized via a one-step hydrothermal method for NRR. In the N-2-saturated Na2SO4 electrolyte, this catalyst exhibited superior catalytic performance to achieve a high NH3 yield (37.2 mu g h(-1) mg(cat.)(-1)) and FE (11.2%) with high stability and selectivity at -0.5 V versus the reversible hydrogen electrode, outperforming other NRR catalysts. According to experimental results, a preferable associative distal pathway was proposed. Density functional theory calculations revealed that the NRR process can proceed preferably on Fe atoms instead of S atoms, and the conversion of *NH2 to *NH3 was the potential-determining step with an energy barrier of 0.45 eV. Therefore, this work offers a new avenue to prepare high-efficiency and highly selective transition-metal-based catalysts for NRR under ambient conditions.