One-pot photoassisted synthesis, in situ photocatalytic testing for hydrogen generation and the mechanism of binary nitrogen and copper promoted titanium dioxide

Abstract

For the sustainable production of hydrogen by photocatalysis, the use of renewable resources such as water, organic compounds from plant biomass and earth abundant metal promoters is desired. We herein describe the previously not reported “one-pot” photoassisted synthesis of a binary metal–nitrogen promoted Cu(0)–N-TiO₂ photocatalyst from a N-TiO₂ precursor by photodeposition of copper directly in the photocatalytic suspension. The N-TiO₂ contains nanocrystalline anatase as found by XRD and Raman spectroscopy. X-ray Photoelectron Spectroscopy (XPS) and Electron Spin Resonance (ESR) spectroscopy indicate that a nitrogen promoter is present as a substitutional site. The scheme of relaxation of a photoexcited charge through a substitutional nitrogen induced midgap states in N-TiO₂ is proposed. The binary promoted Cu(0)–N-TiO₂ photocatalyst prepared from N-TiO₂ by “one-pot” photodeposition of copper in the suspension showed a high activity in the in situ hydrogen generation under near-UV/visible light with glycerol in water, up to 675 μmol g⁻¹ h⁻¹. The “one-pot” photoassisted synthesis and mechanism of operation of the Cu(0)–N-TiO₂ photocatalyst are studied by the complementary in situ spectroscopic methods.