M/TiO2 (M = Fe, Co, Ni, Cu, Zn) catalysts for photocatalytic hydrogen production under UV and visible light irradiation

Abstract

In order to improve the photocatalytic response of TiO2 to UV and visible light for hydrogen photoproduction, low cost M/TiO2 semiconductor catalysts were prepared by the impregnation method of five different first row transition metals (M = Fe, Co, Ni, Cu or Zn) on a commercial titania support. The maximum hydrogen production efficiency was achieved for the Cu/TiO2 photocatalyst, with ∼5000 and ∼220 μmol h−1 g−1 H2 production rates for UV and visible irradiation, respectively. Ni/TiO2 and Co/TiO2 also showed a significant photocatalytic activity when UV light was used. The best performing catalyst, Cu/TiO2, was characterized by TEM and XPS measurements. The data showed that Cu was highly dispersed over the TiO2 support and the copper species existed as both reduced Cu0/Cu+ and oxidized Cu2+ on TiO2. Besides, during the hydrogen production reaction, the reduced Cu was partially oxidized to Cu2+ by the transfer of photogenerated holes under UV or visible light irradiation. With UV and visible lamps, the H2 production rates were higher than those obtained with non-impregnated TiO2 by factors of 16 and 3, respectively. These results demonstrated that a Cu/TiO2 photocatalyst could be considered a promising low-cost alternative to the well-known Pt/TiO2 system for hydrogen production, making the Cu-based catalyst an ideal cost-effective candidate for this reaction