Photocatalytic generation of H2 by photoreforming of organics in aqueous suspension of Nb2O5/C3N4 composites

Bare and composite materials based on C3N4 and Nb2O5 have been used as photocatalysts for the photoreforming of aqueous solutions of oxygenated compounds. Both Nb2O5 and Nb2O5/C3N4 composites have been prepared by hydrothermal synthesis and all of them were physical-chemically characterized. In this work two different carbon nitride species i.e. graphitic (g-C3N4) or thermo-etched (TE-C3N4) were used both alone or coupled with Nb2O5. The photo-reforming activity has been measured under UV irradiation by using the semiconductors in the presence of Pt as co-catalysts and, in the case of the best material, it was, for the first time, measured and compared also under natural solar irradiation. It was found that the highest activity was achieved with the Nb2O5/TE-C3N4 10:1-200 photocatalyst for which the hydrogen formation under UV irradiation resulted of ca. 46 mmol·h-1·g-1 with an apparent quantum yield of ca. 14 %. The maximum solar hydrogen productivity was 1.8 mmol·kJ-1·g-1 or 0.81 mmol·h-1·g-1.