Synergy in Pd/Cu2O heteronanostructure boosts the electrochemical conversion of nitrate to ammonia

Developing highly selective and active electrocatalysts for the NO3− reduction reaction (NO3RR) has attracted significant interest. Here, we improved the catalytic performance via surface decorating the Cu2O catalyst with palladium (Pd) clusters, which are expected to facilitate the hydrogenation of NO3− due to their strong affinity for hydrogen. The prepared catalyst exhibited a high NH3 yield rate of 0.555 mmol h−1 cm−2 (2.79 mmol h−1 mg−1catalyst) and a remarkable faradaic efficiency (FE) of 95.8%, which is attributed to the numerous heterointerfaces between Cu2O and Pd clusters on the catalytic surface. Density functional theory calculations provided insights into the role of the newly introduced active sites in promoting NO3RR, thereby explaining the superior activity of the Pd cluster-decorated Cu2O catalyst. The formation of copper domains during the NO3RR also suppressed the competing reaction, the hydrogen evolution reaction, which has led to increased NH3 FE and NO3RR activity over multiple catalytic cycles.