From the Haber–Bosch Process to the Green Ammonia Production: Advances and Challenges in Photocatalytic Ammonia Synthesis

ABSTRACT As a basic industrial material and a promising green energy carrier, ammonia (NH 3 ) is widely utilized in agriculture, chemical industry, and energy sector. Nevertheless, the traditional Haber–Bosch process continues to encounter sustainability bottlenecks. It operates under extreme temperature and pressure conditions, leading to intensive energy demands and high carbon emissions. In recent years, photocatalytic ammonia synthesis has emerged as a sustainable alternative to the Haber–Bosch process. This article provides a systematic review of the reaction mechanisms of pNRR, theoretical and experimental research methods, catalyst design strategies, the application of AI, as well as experimental reaction systems and detection methods. Furthermore, this work provides a systematic evaluation of analytical methods, including indophenol blue, Nessler's reagent, ion chromatography, and NMR, by quantifying their susceptibility to interferences from sacrificial agents, metal ions, and sulfide species. A practical method‐selection framework is established to guide researchers in matching detection protocols to specific reaction configurations. This review aims to provide an overview of recent advances and challenges in photocatalytic ammonia synthesis and ideas for the development of industrial green ammonia production.