Synthesis And Photocatalytic Hydrogen Production Performance Of S,N-doped 1D TiO₂ Nanomaterials

The increasingly serious energy crisis and the environmental contamination caused by the burning of fossil fuels have led to an aggressive search for renewable and environmental-friendly alternative energy recourses. Hydrogen energy has been recognized as a potentially significant alternative form of storable and clean energy for the future. Since the discovery of water photolysis on a TiO2 photoanode in the 1970s, TiO2 is regarded as a benchmark photocatalyst for hydrogen production through water splitting under ultravoilet irradiation. In order to narrow its band gap (3.2 eV) and extend its working spectrum to the visible light region, doping with non-metal elements has been used to tune TiO2 electronic structure, which builds acceptor states above the valence band from the p states of non-metal ions. Fortunately, it is demonstrated that one-dimensional (1D) nanostructures have the abilities to effectively inhibit the recombination of the electron-hole pairs due to the fact that the charge pairs can be spatially separated and the electrons are transported to the surface active sites rapidly.Based on the above comprehensive analysis, a facile sulfidizing approach has been developed for preparing a serial of 9 nm S-doped TiO2 nanotube photocatalysts with reduced band gaps, which have a highest H2-production rate of 9.61 mmol h-1 g-1 under visible-light irradiation and the quantum efficiency (QE) reaches 19.8% at the wavelength of 420 nm. In the products, except the function of S doping, the nanotube with layered-structure also provides a more optimized geometry with significantly shortened carriers paths and H2O molecules diff-usion in the tube-walls.Doping with non-metal dements has been used to tune TiO2 electronic structure,which builds acceptor states above the valence band from the p states of non-metal ions. At the same time, the doping also brings new charge-carrier trapping and recombination centres,which correspondingly results in the quantum efficiency losses caused by the charge pair recombination. Here, we report a mechanistic study on a novel nanotube structure that overcomes the drawback. Anatase N-dopd TiO2 nanotubes with two dominant surfaces of(101) and (001) facet exhibit enhanced photocatalytic activity, which have a higher H2-production rate of 10.87 mmol h-1 g-1 under visible-light irradiation. Furthermore, the mechanism for enhanced phtocatalytic abilities in the N-doped TiO2 nanotubes system has also been proposed.Although, N-doped TiO2 nanotubes with two dominant surfaces of (101) and (001)facet exhibit enhanced photocatalytic activity. However,with the increasing content of nitrogen, TiO2 nanotubes would be destroyed. Therefore, to enhance nitrogen content, the stable TiO2 nanobelts have been proposed. N-doped TiO2 nanobelts with two dominant surfaces of (101) and (001) facet exhibit enhanced photocatalytic activity, which have a higher H2-production rate of 670 ?mol h-1 g-1 under visible-light irradiation. Moreover, the mechanism for enhanced photocatalytic abilities in the N-doped TiO2 nanobelts system has also been proposed.