Emerging strategies for catalytic ammonia synthesis: novel energy-input pathways and regulation of catalyst electronic structure.

Conventional ammonia synthesis via the Haber-Bosch process is constrained by severe thermodynamic and kinetic limitations, motivating the development of alternative catalytic strategies under mild conditions. Although extensive efforts have been devoted to plasma-assisted catalysis, electrocatalysis, photocatalysis, and other alternative ammonia synthesis routes, existing reviews have primarily summarized these developments. However, the common physical principles underlying many emerging catalytic strategies remain insufficiently discussed. Here, we review recent advances from a mechanism-oriented physical perspective, organized into two categories: novel energy-input pathways, which deliver energy through mechanochemical activation, microdroplet interfacial electric fields, photothermal conversion, laser irradiation, and ionizing radiation; and regulation of catalyst electronic structure, which operates through spin polarization, color-center defect, and plasmonic excitation. We hope that it can provide a useful framework for understanding emerging ammonia synthesis strategies and for guiding the rational design of next-generation catalytic systems.