Advances in electrocatalytic nitrate reduction to ammonia over Cu-based catalysts

Ammonia (NH₃) is a critical basic material for both the agricultural and pharmaceutical industries. Traditionally, NH₃ synthesis has relied on the Haber-Bosch process, which is characterized by high greenhouse gas emissions and stringent reaction conditions. As a more sustainable and cost-effective alternative, electrocatalytic NH₃ synthesis has gained increasing attention. Nitrate (NO₃^-), a common pollutant in water and soil, is considered a promising nitrogen source for NH₃ production due to its high solubility and relatively low N=O bond dissociation energy. This makes it particularly suitable for electrocatalytic nitrate reduction to ammonia (NRA), a process with significant potential for addressing nitrate pollution while contributing to NH₃ production. However, challenges such as slow reaction kinetics and poor product selectivity persist in the NRA process. To overcome these challenges, the selection and optimization of catalysts are crucial for improving NRA performance. Among the various catalysts explored, copper-based (Cu) catalysts have attracted widespread attention due to their unique electronic structure and outstanding catalytic performance. This review provides a comprehensive analysis of the application and reaction mechanisms of Cu-based catalysts in NRA, along with an overview of testing systems and evaluation metrics used in the field. Additionally, it highlights current challenges and outlines future research directions to support the continued development of Cu-based materials for NRA applications.