Hydrogen Production from Aqueous Glucose Solutions over g-C3N4/Pt/TiO2 Photocatalysts

Abstract

In this work, a series of composite photocatalysts based on graphitic carbon nitride and platinized titanium dioxide was synthesized and the reaction kinetics of photocatalytic hydrogen evolution from aqueous solutions of glucose under the visible light irradiation (440 nm) was studied. The graphitic carbon nitride was prepared by the thermal polycondensation of melamine at 600°C with the subsequent thermal exfoliation. The g-C₃N₄/Pt/TiO₂ composite photocatalysts were produced by the self-assembly of g-C₃N₄ and Pt/TiO₂. Varying the g-C₃N₄ content showed that the sample containing 10 wt % g-C₃N₄ had the highest activity. The dependence of the rate of hydrogen evolution on the initial glucose concentration obeyed the Langmuir–Hinshelwood equation; the adsorption constant was K_ads = 76 ± 14 M^–1, and the apparent rate constant was k_r = 0.69 ± 0.02 μmol/min. The photocatalyst 10% g-C₃N₄/1% Pt/TiO₂ was studied using X-ray photoelectron spectroscopy both before and after the reaction of hydrogen evolution. It was found that a portion of platinum in the initial photocatalyst was present in the oxidized state (+2), and platinum was completely reduced to a metallic state during the photocatalytic reaction. The activity of the photocatalyst 10% g-C₃N₄/1% Pt/TiO₂ under the solar simulator light irradiation (AM1.5G) was 560 μmol h^–1 g^–1.