Descriptor-guided atomic-scale engineering of single-atom catalysts for electrochemical nitrogen reduction.

Abstract

Electrochemical nitrogen reduction reaction (eNRR) offers a sustainable pathway for ammonia synthesis under ambient conditions; however, its practical implementation remains hindered by the inertness of the NN bond, limited N2 activation, and the competing hydrogen evolution reaction (HER). Single-atom catalysts (SACs), comprising isolated metal atoms anchored on engineered supports, have emerged as a promising platform due to their maximum atomic utilization, well-defined active sites, and tunable electronic structures. In this review, we systematically summarize recent advances in atomic-scale engineering strategies-namely coordination engineering, heteroatom doping, defect engineering, and strain modulation-that govern the activity and selectivity of SACs for eNRR. These approaches collectively regulate the geometric and electronic environments of active centers, influencing charge redistribution, orbital hybridization, N2 adsorption, and reaction energetics, while also enabling suppression of HER. Importantly, we highlight the growing role of descriptor-based design principles in establishing unified structure-activity relationships. By correlating geometric descriptors (e.g., coordination number, bond length, and local symmetry) and electronic descriptors (including d-band center, charge transfer, spin state, and adsorption-free energies of key intermediates) with catalytic performance, a predictive framework for rational SAC design is established. Furthermore, the importance of realistic theoretical modelling of the electrode-electrolyte interface is emphasized, as it provides deeper insight into potential-dependent mechanisms, interfacial effects, and dynamic evolution of active sites under operating conditions. Finally, key challenges-including catalyst stability, scaling limitations, HER competition, and synthesis scalability-are critically discussed, along with future directions integrating advanced synthesis, operando characterization, and data-driven modelling. This review provides comprehensive guidelines for the rational development of efficient, selective, and durable SACs toward practical electrochemical nitrogen fixation.