Advanced photocatalysis enabled by water-state-driven interface design

Photocatalytic conversion of abundant gaseous small molecules on Earth (such as CO₂, N₂, and O₂) into high-value chemicals is a promising strategy for renewable fuel production and environmental remediation. However, conventional gas–liquid photocatalytic interfaces face three unavoidable bottlenecks. Poor utilization of solar energy, rapid charge carrier recombination, and sluggish mass transfer limit the efficiencies of solar-to-fuel processes and the widespread application of photocatalysis in industry. Recent advances in water-state interface engineering, namely utilizing liquid, microdroplet, and vapor phases, have demonstrated unprecedented performance enhancements for earth-abundant gas conversions. This review critically analyzes mechanistic principles of phase-tailored photocatalyst design, elucidates interfacial charge and mass transfer dynamics, and discusses structure–activity relationships in CO₂ reduction, N₂ fixation, and H₂O₂ synthesis. Supported by recent experimental data, we highlight emerging opportunities in metastable interface engineering, offering actionable insights to overcome limitations in bi-phase systems. These innovations are critical for scalable solar chemical production, advancing the industrialization of photocatalytic technologies.