Mesoporous SiO2-confined Pt-loaded dye-sensitized Nano-ZnO for visible-light H2 evolution

Introduction: Efficient visible-light-driven hydrogen evolution requires overcoming the intrinsic limitations of wide-band-gap semiconductors such as ZnO, particularly poor visible absorption and inefficient interfacial charge transfer. Engineering dye–semiconductor interactions within confined architectures offers a pathway to enhance photosensitization and catalytic performance. Hybrid photocatalysts for visible-light-driven hydrogen evolution were developed by integrating organic dyes (proflavine and hemicyanine LDS-698) with Nano-ZnO confined within ordered mesoporous silica matrices (MCM-41 and SBA-15). Materials and methods: Nano-ZnO were first introduced into the mesoporous frameworks through impregnation followed by hydrolysis-assisted formation, generating highly dispersed ZnO nanostructures within the mesoporous channels, followed by encapsulation of proflavine or LDS-698 dyes. Pt nanoparticles were subsequently photodeposited as cocatalysts. The resulting hybrid materials were systematically characterized using structural, spectroscopic, and microscopic techniques to confirm the successful incorporation. Steady-state and time-resolved fluorescence spectroscopy were employed to probe excited-state dynamics and charge transfer behavior. Photocatalytic hydrogen evolution was evaluated under visible-light irradiation using triethylamine as a sacrificial electron donor. Results: Characterization confirmed the formation of highly dispersed Nano-ZnO within intact mesoporous frameworks and successful dye incorporation. Confinement induced modifications in photophysical properties, including fluorescence quenching and prolonged excited-state lifetimes, indicating efficient electronic coupling and photoinduced electron transfer from dyes to ZnO. In contrast to solution-phase systems, confined architectures enabled effective dye–semiconductor interactions. The Pt-loaded, dye-sensitized hybrids exhibited significantly enhanced hydrogen evolution, achieving rates up to 112 µmol h−1 g−1, markedly higher than pristine ZnO. The use of Pt was intended to standardize the HER interface and isolate the effects of confinement and photosensitization. Conclusions: Mesoporous confinement effectively enhances dye-sensitized photocatalysis by promoting intimate dye–ZnO interactions, suppressing aggregation, and facilitating efficient charge injection, highlighting the potential of mesoporous hybrid systems for efficient solar-to-hydrogen energy conversion.