Enhancement of hydrogen production of a Cu–TiO2 nanocomposite photocatalyst combined with broad spectrum absorption sensitizer Erythrosin B

Abstract

A broad spectrum absorption photocatalytic system has been expected for a long time, especially for catalysts where the absorption mainly concentrates on the ultraviolet region, like TiO₂. Here, dye sensitization was used to realize this expectation for TiO₂. Anatase TiO₂ was prepared by a hydrothermal method and then modified with Cu nanoparticles (NPs) by chemical reduction reaction. The highest H₂ production rate was 3.33 mmol g⁻¹ h⁻¹ for Cu(3%)–TiO₂ (content of Cu NPs was 3 wt%) and for pure TiO₂ was only 0.356 mmol g⁻¹ h⁻¹. Next, the Cu(3%)–TiO₂ photocatalyst was sensitized with various amounts of Erythrosin B (ErB) and the highest H₂ production rate was 13.4 mmol g⁻¹ h⁻¹ with 3 mg of ErB in the photoreaction system. Under monochromatic light irradiation (500, 550, 600 and 650 nm), no photocatalytic activity was detected for Cu(3%)–TiO₂ and some photocatalytic activities were obtained for sensitized Cu(3%)–TiO₂, indicating that ErB sensitization can extend the visible light harvesting ability efficiently. Through photoelectrochemical analysis, electron–hole separation and transfer processes were promoted significantly by modification with Cu NPs and then sensitization by ErB. A possible ErB sensitization mechanism is proposed between ErB and Cu–TiO₂ for the improvement of the photocatalytic activity.