CuO/Bi₂CuO₄ Heterostructured Electrocatalyst for the Efficient Reduction of Nitrate to Ammonia

The electrochemical reduction of nitrate to ammonia (NH₃) not only provides an effective approach to balance the perturbed nitrogen cycle for addressing environmental issues but also provides a potential technology for green NH₃ synthesis. However, the process is limited by the produced intermediate-nitrite that tends to accumulate on cathode surfaces and multiple competing reactions. Herein, CuO/Bi₂CuO₄-450 heterostructures are reported as efficient electrocatalysts for the nitrate reduction reaction with extraordinary catalytic activities and selectivities for NH₃ production. The optimized catalyst achieves a remarkable Faradaic efficiency (96.49%) and exceptional NH₃ yield rate (9.17 mg h^-1 mg_cat.^-1) at -0.5 V versus RHE, surpassing most of the reported Cu-based catalytic systems. The characterization results and theoretical evidence reveal that the interface effect originating from the strong interaction between Bi₂CuO₄ and CuO tunes the electronic structures of the Cu and Bi active sites for optimized intermediate adsorption and lowers the rate-determining step reaction barriers, resulting in improved catalytic performance. This work offers a strategy to flexibly develop catalysts to promote electrocatalytic techniques for NH₃ production by electrochemical nitrate reduction.