The article discusses the development of a gas–liquid–solid triphase photocatalytic system to enhance the efficiency of the water-gas-shift (WGS) reaction for hydrogen production. Traditional challenges of mass transfer between gaseous CO and liquid H2O in photocatalytic reactions have led to the introduction of this innovative system. By utilizing Rh/TiO2 nanoparticles at the triphase interface, researchers achieved a remarkable H2 production rate of 27.60 mmol g−1 h−1, surpassing rates observed in traditional liquid–solid and gas–solid diphase systems. Finite element simulations supported the stability of CO and H2O concentrations at the gas–liquid–solid interface, indicating efficient mass transfer. This approach lays the groundwork for optimizing the photocatalytic WGS reaction by improving interfacial mass transfer and ensuring a consistent supply of reactants to the photocatalyst's surface, ultimately enhancing hydrogen production efficiency.