Strain relaxation enhances ammonia electrosynthesis from nitrate on Cu/CuAu core/shell nanocrystals with ordered intermetallic layers

Recycling ammonia (NH₃) via the electrocatalytic nitrate reduction reaction (NO₃RR) offers a sustainable, energy-efficient solution for closing the nitrogen cycle while simultaneously treating nitrate-rich wastewater. In this work, we synthesized core/shell Cu/CuAu nanocubes with precisely controlled ordered intermetallic layers using a facile seed-mediated method. The compressive surface strain of the nanocrystals was finely regulated by adjusting the layers of the CuAu shell. Specifically, the strain-relaxed Cu/CuAu catalysts exhibit high NO₃RR performance for NH₃ production, achieving a Faradic efficiency of 89.9% at −0.5 V vs. the reversible hydrogen electrode (RHE) and an exceedingly high yield rate of 11.3 mol h⁻¹ g⁻¹ at −0.6 V vs. RHE. Furthermore, Cu/CuAu catalysts show catalytic stability over 10 consecutive cycles and 12-h electrolysis. This atomic-level control of thickness allows precise tuning of the intrinsic strain to optimize catalytic reactivity, offering a promising strategy to enhance the performance of electrocatalytic ammonia synthesis.