Unlocking Low-Temperature Ammonia Decomposition via an Iron Metal-Organic Framework-Derived Catalyst Under Photo-Thermal Conditions

Photo-thermal catalysis, leveraging both thermal and non-thermal solar contributions, emerges as a sustainable approach for fuel and chemical synthesis. In this study, an Fe-based catalyst derived from a metal-organic framework is presented for efficient photo-thermal ammonia (NH₃) decomposition. Optimal conditions, under light irradiation without external heating, result in a notable 55% NH₃ conversion. Mechanistic investigations reveal that the enhanced catalytic activity arises from the synergistic interplay between light-induced hot carriers and elevated temperatures during irradiation. Supported by density functional theory calculations, the findings elucidate the dual role of the catalyst. At lower temperatures, photo-generated electrons in the Fe₃O₄ phase serve to raise the energies of reaction intermediates, preventing the formation of a thermodynamic sink. Conversely, at higher temperatures, metallic Fe emerges as the predominant active phase, with thermal contributions prevailing. Overall, this work advances the understanding of the cooperative effects between light and heat in photo-thermal systems, paving the way for innovative applications in sustainable energy conversion.