Gas- and Liquid-Phase Catalysts for Solar-Driven Catalytic Ammonia Decomposition

As the transition toward a carbon-neutral hydrogen economy gains increasing attention, photocatalytic ammonia decomposition has received growing interest as a clean and scalable method for hydrogen production. This review critically summarizes recent progress in catalyst development, mechanistic understanding, and performance optimization for solar-driven ammonia decomposition. Photocatalytic systems are categorized by reaction phase (liquid phase and gas phase), and key strategies are discussed, including bandgap tuning, active site engineering, and cocatalyst integration. In addition, emerging approaches such as photothermal enhancement, single-atom catalysis, and machine learning-guided catalyst screening are examined. Current challenges, particularly catalyst deactivation, system-level integration, and scalability, are also highlighted, with a strong emphasis on the scalability of this method. Finally, perspectives are provided for future research aimed at bridging fundamental insights with practical applications. This work offers guidance for the rational design of efficient photocatalysts and contributes to the broader goal of sustainable hydrogen production via solar energy, providing reassurance about the practicality of this approach.