Synergistic composition-structure engineering in PdCu nanoalloys for efficient ammonia electrosynthesis from nitrate...

Electrocatalytic nitrate reduction reaction (NitrRR) has emerged as a promising sustainable alternative for ammonia synthesis via wastewater remediation. However, its practical implementation remains challenged by sluggish reaction kinetics and limited selectivity. Herein, we demonstrate a microfluidic strategy to achieve the synergistic composition-structure engineering of the ultrasmall (∼24 nm) PdCu nanoparticles (NPs). The well-designed PdCu NPs exhibit exceptional NitrRR performance, achieving an ammonia yield of 89.70 mg h^-1 mg_cat.^-1 at -0.8 V vs RHE. The synergistic electronic interaction within the bimetallic system, involving electron transfer from Cu to Pd, optimizes intermediate adsorption and thereby lowers the energy barrier of the rate-determining step (RDS, *NO→*HNO) by up to 0.17 eV. The composition-dependent trade-off was further elucidated, with Pd-rich sites favoring the competing hydrogen evolution reaction while Cu-rich sites required higher overpotentials. An optimal balance between these effects was struck, achieving a Faradaic efficiency of 92.03 %. Moreover, the engineered pore-channel network significantly enhances mass transport and active site accessibility, accelerating ammonia production kinetics. These findings establish fundamental design principles for advanced NitrRR electrocatalysts, thereby paving the way for sustainable solutions to pressing environmental and energy challenges.