Advances and Mechanistic Studies of Cu-Based Heterostructures for Nitrate Reduction

Ammonia is a carrier of high-energy density and a key component of agricultural fertilizers. Conventionally, the large-scale Haber-Bosch synthesis of ammonia necessitates harsh temperatures and pressures in excess of >500 °C and >200 atm, respectively, leading to considerable greenhouse gas emissions. Simultaneously, the intense use of nitrogen fertilizers and their discharge as agricultural waste have resulted in widespread nitrate accumulation in aquatic environments, posing serious risks to human health and ecological balance. To mitigate these challenges, the nitrate reduction reaction (NO₃RR) to ammonia has become an attractive green alternative, offering the dual benefits of pollutant remediation and decentralized, sustainable ammonia production. Among various materials, copper-containing electrocatalysts stand out because of their favorable electronic structure, which promotes efficient nitrate adsorption and reduction while suppressing the competing hydrogen evolution reaction (HER). Furthermore, the construction of Cu-based heterostructures introduces interfacial effects that can modulate electronic configurations and optimize the distribution of active sites, thereby enhancing the catalytic activity and selectivity. This review discusses exclusively copper-based electrocatalysts and systematically highlights recent progress in heterostructure design for the NO₃RR. We provide a critical overview of the reaction mechanisms, interfacial engineering strategies, and structure-activity relationships that are most valuable for the judicious construction of next-generation Cu-containing heterostructures as efficient electrocatalysts for sustainable ammonia production.