Enhanced Photocatalytic Hydrogen Evolution via Optimized Coating Strategies for Photo Flow Reactors

The development of scalable and durable photocatalyst coatings is key to advancing solar-driven hydrogen production under continuous flow conditions. In this work, a slot-die coating method was applied to deposit uniform TiO₂ films with tunable porosity, adhesion, and optical properties. The addition of colloidal SiO₂ and CaCl₂ enabled mechanically stable coatings with enhanced light transmission and bubble release. Systematic variation of TiO₂ loading revealed a balance between light absorption and catalyst utilization: excessive loadings caused light shielding and recombination, whereas low loadings limited active sites for H₂ generation. The optimized coating, containing 2.5 µL mL⁻¹ LUDOX AS-40 and 0.6 mg mL⁻¹ CaCl₂, achieved a maximum hydrogen evolution rate of 7.3 g H₂ m⁻² h⁻¹ at a TiO₂ loading of 700 µg cm⁻² and a specific activity of 0.89 g H₂ gTiO₂⁻¹ h⁻¹. The reactor operated stably for over 100 hours with a quantum efficiency of 65 %, demonstrating both robustness and scalability. This study establishes direct correlations between coating composition, morphology, and photoactivity, providing a design framework for efficient photocatalytic flow reactors.