Boosting Electrocatalytic NO Reduction via Intermediate Adsorption Modulation on Synergistic CuCo Bimetallic Oxide Catalysts

Abstract

Cobalt-based catalysts are extensively employed in the electrocatalytic nitric oxide reduction reaction (NORR) for ammonia synthesis due to their superior ammonia selectivity. However, their practical implementation is significantly hindered by insufficient adsorption capacity toward NO and critical intermediates. To address this limitation, we strategically integrated copper (Cu) into a cobalt (Co) matrix through hydrothermal synthesis followed by controlled annealing, resulting in a well-dispersed CuCo bimetallic catalyst (CuCo₃O_x-650). This catalyst exhibits exceptional electrochemical performance, delivering an NH₃ generation rate of 312.1 μmol h^-1 cm^-2 at -0.5 V with a Faradaic efficiency (FE) of 90.8%. Density-functional-theory analysis indicates that Co atoms serve as the principal conduits for charge transfer during NO adsorption on CoCuO₂, while Cu incorporation induces supplementary electron redistribution, upshifting the d-band center and strengthening the binding of NO and intermediates (e.g., *NH_x). Remarkably, the adsorption energy of *H on CuCo₃O_x-650 is merely 1/7 that for NO, effectively suppressing the competing hydrogen evolution reaction (HER) by minimizing parasitic *H accumulation. The synergistic interplay between Co and Cu optimizes both the activity and selectivity for NO-to-NH₃ conversion. Furthermore, when a Zn-NO battery is operated with the cathode, CuCo₃O_x-650 achieves a peak power density of 5.57 mW cm^-2 and an ammonia production rate of 438.44 μg h^-1 cm^-2, showcasing its dual functionality in energy conversion and environmental remediation.

Keywords: Ammonia synthesis; CuCo bimetallic catalyst; Electroreduction process; Intermediate adsorption; NO reduction.