Synthesis of Pd-Integrated Carbon Dot@TiO2 Thin Film for Photocatalytic Glycerol Reforming Reaction for Producing Hydrogen.

Abstract

A series of thin-film photocatalysts comprising TiO₂ modified with carbon dots (CDs) dispersed either with palladium (Pd-CD/TiO₂) or nickel (Ni-CD/TiO₂) were synthesized via solid-state and wet-impregnation methods. Morphological characterization (HR-TEM, SEM-EDS) confirmed the anatase phase of TiO₂ and the atomic dispersion of metal-integrated CDs on its surface. UV-vis DRS and XPS analyses revealed a marginal red shift in band-gap and the presence of sp²-hybridized graphitic carbon, and metal-carbon interactions, indicating enhanced light absorption and charge separation through Schottky junctions. Under direct sunlight illumination, Pd-CD/TiO₂ thin film exhibited superior hydrogen yield (1167 µmol g^-1 h^-1) and maintained stability over 25 h, outperforming Ni-CD/TiO₂ (494 µmol g^-1 h^-1) and bare TiO₂ (166 µmol g^-1 h^-1) photocatalyst thin films. Concurrent glycerol oxidation at neutral pH (pH∼7) yields glycolaldehyde (41% selectivity), formic acid, and dihydroxyacetone as value-added products. Enhanced photocurrent density and lower impedance of Pd-CD/TiO₂ corroborate improved charge carrier separation and dynamics. The results demonstrate that Pd-CD synergistically improves the photocatalytic performance of the Pd-CD/TiO₂ for sustainable hydrogen generation and selective biomass valorization.