Neutral Electrocatalytic Ammonia Synthesis from Nitrate over a Cu2O-Co(OH)2 Composite Electrode

Electrocatalytic nitrate reduction reaction (NO3RR) provides a sustainable and carbon-neutral alternative to the energy-intensive Haber–Bosch process for ammonia production. Operating directly in neutral media is particularly attractive for practical implementation, as it avoids corrosive acids/alkalis and aligns with wastewater remediation scenarios, yet it suffers from sluggish reaction kinetics and poor product selectivity due to the competing hydrogen evolution and the multistep electron/proton transfer nature. In this study, a Cu2O-Co(OH)2 composite electrode supported on cobalt foam (Cu2O-Co(OH)2/CF) was constructed to enhance nitrate reduction under neutral conditions. The introduction of Cu2O promotes the initial activation of NO3− and facilitates its conversion to NO2−, while Co(OH)2 favors the subsequent hydrogenation of NO2− and other nitrogen-containing intermediates. At −1.0 V (vs. RHE), the Cu2O-Co(OH)2/CF electrode achieves an ammonia production rate of 1.1 mmol·h−1·cm−2. In situ infrared spectroscopy reveals that Cu2O enhances the evolution of intermediates associated with the initial nitrate reduction, whereas Co(OH)2 promotes the subsequent conversion of nitrogen-containing intermediates, which demonstrate that the synergistic regulation of different reaction stages by Cu2O and Co(OH)2 facilitates the stepwise reduction of NO3− to NH3. This work demonstrates that the staged catalytic functions, enabled by the spatially separated active sites, can successfully overcome the kinetic bottleneck of neutral NO3RR, offering a promising electrode design for practical ammonia synthesis.