Triphase photocatalytic water-gas-shift reaction for hydrogen production with enhanced interfacial diffusion at gas-liquid-solid interfaces

The exothermic characteristic of the water-gas-shift (WGS) reaction, coupled with the thermodynamic constraints at elevated temperatures, has spurred a research inclination towards conducting the WGS reaction at reduced temperatures. Nonetheless, the challenge of achieving efficient mass transfer between gaseous CO and liquid H2O at the photocatalytic interface under mild reaction conditions hinders the advancement of the photocatalytic WGS reaction. In this study, we introduce a gas-liquid-solid triphase photocatalytic WGS reaction system. This system facilitates swift transportation of gaseous CO to the photocatalyst's surface while ensuring a consistent water supply. Among various metal-loaded TiO2 photocatalysts, Rh/TiO2 nanoparticles positioned at the triphase interface demonstrated an impressive H2 production rate of 27.60 mmol g-1 h-1. This rate is roughly 2 and 10 times greater than that observed in the liquid-solid and gas-solid diphase systems. Additionally, finite element simulations indicate that the concentrations of CO and H2O at the gas-liquid-solid interface remain stable. This suggests that the triphase interface establishes a conducive microenvironment with sufficient CO and H2O supply to the surface of photocatalysts. These insights offer a foundational approach to enhance the interfacial mass transfer of gaseous CO and liquid H2O, thereby optimizing the photocatalytic WGS reaction's efficiency.Keywords: Water-gas-shift; Photocatalysis; Triphase interface; Hydrogen evolution; TiO2.