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

A high-aspect-ratio Ag/Co 3 O 4 nanowire array catalyst is fabricated via in-situ growth and interfacial engineering, forming a tandem catalytic system with synergistic Ag and Co active sites. • Ag loading promotes interface electron transfer and increases the proportion of Co 3+ to optimize the reaction pathway and suppress hydrogen evolution reaction. • The tailored interface provides abundant active sites and fast kinetics, leading to a record 94.2% FE at 800 mA·cm -2 . • Maintains >90% FE at 1 A·cm -2 , showcasing unmatched stability for scalable application. Electrocatalytic conversion of nitrate (NO 3 - ) to ammonia (NH 3 ) offers an beneficial route for green NH 3 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/Co 3 O 4 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 Co 3+ , which can promote yield improvement. Electrochemical tests show that in an H-cell, Ag/Co 3 O 4 achieves a Faradaic efficiency (FE) of 91.4% and NH 3 rate of 70.2 mg·h -1 ·cm -2 at −0.4 V vs . RHE. In a membrane electrode assembly (MEA) system, Ag/Co 3 O 4 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 Co 3+ active center, providing a novel strategy for designing high-performance and robust catalysts for the electrochemical nitrate reduction reaction (NO 3 RR) and advancing this technology toward industrial application. Download: Download high-res image (518KB) Download: Download full-size image