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.