Selective Electrochemical NO_x Reduction to N₂ for Sustainable Ammonia Energy Systems

Ammonia-based energy systems offer a pathway toward carbon-free energy, yet NO_x emissions from ammonia combustion hinder the realization of a sustainable closed-loop. Electrochemical NO_x reduction reaction (eNO_xRR) provides a promising route to convert NO_x to benign N₂ under mild conditions. However, under the low NO_x concentrations typical of practical exhaust streams, N₂ selectivity is limited by competing hydrogenation, hydrogen evolution, and inefficient intermediate utilization. Here, we present a mechanistic perspective on selective NO_x-to-N₂ conversion, highlighting that eNO_xRR proceeds through *NO-mediated pathways with N₂O as a key intermediate, while low surface coverage restricts N-N coupling. We propose that integrating tandem catalysis with interfacial microenvironment regulation offers a unified strategy to enhance N₂ selectivity. Finally, we outline key challenges for practical implementation under gas-phase and dilute conditions, providing design principles for efficient electrochemical denitrification. This framework has the potential to enable scalable NO_x removal and support a closed-loop ammonia energy system.