Pd Nanoparticle Size‐Dependent H* Coverage for Cu‐Catalyzed Nitrate Electro‐Reduction to Ammonia in Neutral Electrolyte

Abstract

AbstractElectrochemical conversion of nitrate (NO3−) to ammonia (NH3) is an effective approach to reduce nitrate pollutants in the environment and also a promising low‐temperature, low‐pressure method for ammonia synthesis. However, adequate H* intermediates are highly expected for NO3− hydrogenation, while suppressing competitive hydrogen evolution. Herein, the effect of H* coverage on the NO3RR for ammonia synthesis by Cu electrocatalysts is investigated. The H* coverage can be adjusted by changing Pd nanoparticle sizes. The optimized Pd@Cu with an average Pd size of 2.88 nm shows the best activity for NO3RR, achieving a maximum Faradaic efficiency of 97% (at −0.8 V vs RHE) and an NH3 yield of 21 mg h−1 cm−2, from an industrial wastewater level of 500 ppm NO3–. In situ electrochemical experiments indicate that Pd particles with 2.88 nm can promote NO3− hydrogenation to NH3 via well‐modulated coverage of adsorbed H* species. Coupling the anodic glycerol oxidation reaction, ammonium and formate are successfully obtained as value‐added products in a membrane electrode assembly electrolyzer. This work provides a feasible strategy for obtaining size‐dependent H* intermediates for hydrogenation.