Interfacial Synergistic Hydrogen Spillover and Electron Transfer for Boosting Electrocatalytic Nitrate Reduction to Ammonia.

Abstract

Nitrate overabundance in wastewater brings environmental pollution and health risks, while the traditional Haber-Bosch process for ammonia production is accompanied by huge energy consumption and carbon emissions. Electrocatalytic nitrate reduction reaction (NO₃ ^-RR) can use renewable energy to produce green ammonia and provide a sustainable route for wastewater treatment. Electrochemical NO₃ ^-RR process involves multiple proton-coupled-electron steps; however, simultaneous optimization of proton and electron transfer is still challenging, leading to poor selectivity for ammonia production. Here, the interfacial synergism of hydrogen spillover and electron transfer is demonstrated to boost electrocatalytic nitrate reduction to ammonia. Experimental and theoretical calculation results show that the interface hydrogen spillover of CoNi-layered double hydroxide (LDH) accelerates the hydrogenation step of NO₃ ^-RR, while the electron transfer to Cu₂O promotes the reduction of adsorbed NO₃ ^-. Benefitting from the interfacial synergistic hydrogen spillover and electron transfer, the CoNi-LDH@Cu₂O catalyst achieves a remarkable Faradaic efficiency of 97.8% at -0.3 V versus RHE, and a high NH₃ yield rate of 75.2 mg h^-1 cm^-2 at an industrial-relevant current density ≈1 A cm^-2. This work provides insights into the interface design strategy to enhance NO₃ ^-RR performance for waste nitrate treatment and green ammonia synthesis.