Recent advances in photocatalytic ammonia synthesis: materials design and mechanistic insights

Ammonia, a core raw material for the global agricultural and chemical industries, faces serious challenges in its conventional synthesis process (the Haber-Bosch method) due to its high energy consumption, high carbon emissions and dependence on fossil fuels. Photocatalytic ammonia synthesis technology provides a revolutionary solution for green ammonia economy by realizing efficient nitrogen reduction under mild conditions with solar energy as the driving force. In this study, we systematically review the mechanism of photocatalytic nitrogen reduction reaction, focusing on the adsorption activation of nitrogen molecules, electron transfer pathways, and intermediate product regulation strategies, and review multiple types of photocatalyst systems including metal oxides, sulfides, bismuth-based materials, and carbon-based materials. Modification strategies such as defect engineering, single-atom modification, heterojunction design and plasma effect can significantly optimize the light absorption range, suppress the carrier recombination and enhance the active site density. It is further pointed out that the existing catalytic systems still face bottlenecks such as low quantum efficiency, photocorrosion, and scale-up reactor design, and future studies are needed to promote the photocatalytic synthesis of ammonia from the laboratory to the industry through multiscale synergistic innovation. This study provides theoretical guidance and a practical framework for the design and development of an efficient and stable photocatalytic ammonia synthesis system, which is scientifically important for achieving the goal of carbon neutrality.