Wide-Ph-Range Adaptable Ammonia Electrosynthesis from Nitrate on Cu-Pd Interfaces

Ammonia production via electrochemical nitrate reduction is essential for environmental protection and the hydrogen economy. However, high Faradaic efficiencies (FE) of NH3 cannot be obtained under strong acid or alkaline conditions due to the uncontrollable adsorption energy and coverage of hydrogen species (H*) on active sites. This paper describes the design and fabrication of a copper-palladium (Cu-Pd) alloy nanocrystal catalyst that inhibits H2 and nitrite generation in electrolytes with different nitrate concentrations and varied pH. The interfacial sites of Cu-Pd alloys could enhance the adsorption energy and coverage of H* while increasing the reaction rate constant of NO2*-to-NO*, which achieves a rapid conversion of NO2* along with a decreased FE of NO2-. Under ambient conditions, optimal FE(NH3) is close to 100% at a wide pH range, with a solar-to-chemical conversion efficiency of 4.29%. Thermodynamics and kinetics investigations offer new insights into the reduction mechanism of NO2* for further research.