Electrocatalytic Conversion of Nitrate Into Ammonia Through Heterogeneous Catalysis of NiMoO₄ and Cu/Cu₂O

Abstract

Abstract Facilitating equilibrium in the nitrogen cycle, electrochemical nitrate reduction (NitRR) to ammonia stands as a carbon‐free method for ammonia synthesis. Copper‐based catalysts, renowned for NitRR, face a hurdle in supplying sufficient hydrogen radicals (*H) for efficient hydrogenation of NitRR intermediates. Addressing this, NiMoO 4 is leveraged as an excellent *H donor, synergistically coupling it with a copper‐based catalyst. The work introduces a high‐performance NiMoO 4 /CuO nanowire (NW)/Copper foam (CF) catalyst for NitRR, achieving a remarkable Faraday efficiency (FE) of 98.8% and a yield of 0.8221 mmol cm −2 h −1 . Operating at −0.2 V versus reversible hydrogen electrode (vs RHE) in an H‐type electrolytic cell, the catalyst demonstrates exceptional stability over 20 h. Additionally, coupling NitRR with an air stripping process enables efficient collection of NH 4 Cl products, offering a practical avenue for converting waste nitrates into valuable ammonia products. In‐depth in situ electrochemistry and density‐functional theory (DFT) calculations affirm the transformation of CuO into Cu/Cu 2 O during the electrocatalytic reduction process. Cu/Cu 2 O catalyzes nitrate conversion to nitrite, while NiMoO 4 , serving as a *H donor, facilitates deoxidation and hydrogenation of other N intermediates on the Cu/Cu 2 O surface, effectively driving the reduction of nitrate to ammonia.