Selective Electrochemical NO _x Reduction to N ₂ for Sustainable Ammonia Energy Systems

ABSTRACT 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 x RR) provides a promising route to convert NO x to benign N 2 under mild conditions. However, under the low NO x concentrations typical of practical exhaust streams, N 2 selectivity is limited by competing hydrogenation, hydrogen evolution, and inefficient intermediate utilization. Here, we present a mechanistic perspective on selective NO x ‐to‐N 2 conversion, highlighting that eNO x RR proceeds through *NO‐mediated pathways with N 2 O 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 N 2 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.