Electrocatalytic nitrate reduction to ammonia at industrial current densities via interfacial tandem catalysis on Ag/Co3O4

Abstract

Electrocatalytic conversion of nitrate (NO₃⁻) to ammonia (NH₃) offers an beneficial route for green NH₃ synthesis, yet challenges such as complex reaction pathways and uncoordinated adsorption and conversion of reactive species hinder the enhancement of reaction kinetics. In this study, a high-aspect-ratio Ag/Co₃O₄ nanowire array catalyst was successfully fabricated on cobalt foam via an in-situ growth combined with an interfacial engineering strategy, constructing a tandem catalytic system with synergistic Ag and Co active sites. The results demonstrate that Ag loading promotes interface electron transfer and increases proportion of Co³⁺, which can promote yield improvement. Electrochemical tests show that in an H-cell, Ag/Co₃O₄ achieves a Faradaic efficiency (FE) of 91.4% and NH₃ rate of 70.2 mg·h⁻¹·cm⁻² at −0.4 V vs. RHE. In a membrane electrode assembly (MEA) system, Ag/Co₃O₄ exhibits a high FE of 94.2% at large-scale applicable current density of 800 mA·cm⁻² and maintains over 90% FE even at 1000 mA·cm⁻², along with excellent stability. This work elucidates the core mechanism involving tandem catalysis and the synergistic enhancement via interfacial electron transfer regulating Co³⁺ active center, providing a novel strategy for designing high-performance and robust catalysts for the electrochemical nitrate reduction reaction (NO₃RR) and advancing this technology toward industrial application.