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

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 degrees 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 mu mol/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 mu mol h(-1) g(-1).