Perovskite oxide electrocatalysts for selective NO x reduction to ammonia: Material design, reaction mechanisms, and beyond

Abstract

Electrocatalytic NOx reduction, particularly nitrate reduction (NO3RR), has emerged as a promising waste-to-value strategy that simultaneously mitigates nitrogen pollution and enables sustainable ammonia (NH3) synthesis under ambient conditions. Among the various catalyst families, perovskite oxides (ABO3) have attracted considerable attention because their structural flexibility and compositional tunability enable precise regulation of surface electronic structure, defect chemistry, and reaction pathways. In this review, we establish a unified mechanistic framework that links the elementary processes of NOx reduction with rational perovskite design. This framework highlights how symmetry polarization, electronic structure regulation, and hydrogen management collectively govern nitrate activation, intermediate evolution, and selective NH3 formation, and discusses how these mechanistic principles are translated into advanced materials-design strategies, including cation and defect engineering, phase and spatial decoupling, and in situ exsolution of catalytically active nanoparticles. We further emphasize that practical NOx valorization depends not only on catalyst optimization but also on integrating catalyst design with reactor engineering and emerging waste-to-energy electrochemical systems. Finally, we discuss key opportunities for advancing the field through operando characterization, predictive design descriptors, standardized catalyst evaluation, and data-driven materials discovery. This review provides a unified perspective for the rational development of next-generation perovskite electrocatalysts for efficient NOx-to-NH3 conversion, with particular emphasis on nitrate reduction.