Abstract:

Ammonia is an essential chemical feedstock; however, its conventional synthesis via the Haber-Bosch process is associated with high energy consumption and substantial carbon emissions. Developing green and efficient electrocatalytic routes for ammonia synthesis is therefore of significant importance. To overcome sluggish reaction kinetics and limited electron transfer, 26-faceted Cu₂O polyhedra were synthesized using a template-free chemical precipitation method, followed by the deposition of Ag particles onto the Cu₂O surface via photoreduction. This catalyst design optimizes the electronic structure, facilitates interfacial charge transfer, and enhances the intrinsic activity for converting key reaction intermediates (such as *NO₂ and *NH₂OH) into NH₃. As a result, the hydrogen evolution reaction and by-product formation are suppressed, leading to improved electrocatalytic performance for nitrate reduction to ammonia. Electrochemical evaluations demonstrate that Ag-Cu₂O exhibits excellent catalytic activity for the nitrate reduction reaction, achieving a Faradaic efficiency of up to 88%, which outperforms Au-Cu₂O and pristine Cu₂O, while generating lower amounts of the nitrite by-product and the competing hydrogen product. The catalyst maintains effective performance across a wide range of nitrate concentrations, supporting its potential applicability in nitrate wastewater treatment with varying pollutant levels. This study provides new insights into the rational design of high-performance and durable electrocatalysts for nitrate reduction and offers a valuable reference for advancing electrocatalytic technologies in wastewater treatment and green ammonia synthesis.

Key words: electrocatalysis, nitrate reduction to ammonia, photoreduction, silver, copper oxide