The Preparation Of Metal Oxide Photocatalysts And Their Application In Degradation Of Waste Gas And Water Splitting

Photocatalysts were widely used in environment protection,water splitting and photovoltaic cell. Much research set focus on metal oxide photocatalysts because of their stability. In our experimens, a variety of metal oxide photocatalysts were prepared and their photocatalytic performance was investigated.At first, the tubular TiO₂ photocatalysts were successfully synthesized by hydrothermal method. The external tube diameters fall in 8 and 12nm and the internaldiameters are between 5 and 8nm. Moreover, the lengths of the nanotubes are up to 500nm and the specific surface area is approximately 200 m2·g^-1 (the largest can up to 330m2·g^-1), while TiO₂ powders are 78 m2·g^-1. Methylcyclohexane (MCH) was selected as the target pollutant to investigate the photocatalytic performance. The results indicate that TiO₂ nanotubes accelerate the degradation of MCH under the same conditions, comparing with TiO₂ nanoparticles. Finally, the degradation reaction shows a first order kinetics, which was consistent with Langmuir-Hinshelwood equation. Furthermore, many kinds of metal ions were doped into TiO₂ nanotubes. The result showed that the doping of W⁶⁺ can accelerate the rate of photocatalytic oxidation of toluene, and the performance of the photocatalysts would be better than pure TiO₂ nanotubes when W⁶⁺ and TiO₂ mixed with a specific ratio.For enhancing the photoactivity of photocatalysts, assorted metal oxides arrays were prepared by dispensing metal precursor solutions onto fluorine-doped tin oxide-coated glass followed by annealing at 500°C for 3h ( heating rate: 1°C·min^-1). These were screened by scanning electrochemical microscopy with a scanning optical fiber (diameter: 400μm) and the results showed that all Sn-doped Cd-In-Bi, Zn-In, and W-Cd oxide photocatalysts produced enhanced photocurrents for specific metal ratios in 0.1mol·L^-1Na₂SO₃/0.1mol·L^-1Na₂SO₄ electrolyte solution under UV-vis and visible light irradiation, respectively. The products of the photoelectrochemical (PEC) reaction could be detected electrochemically by a Au ring on the optical fiber in 0.1mol·L^-1 Na₂SO₄ soultion. The results show that OH- ions were photooxidized O₂ in this process.Then the spray coating method was selected to synthesize the photocatalyst film electrodes on FTO. The photoelectrochemistry (PEC) properties of larger film electrodes were investigated in 0.1mol·L^-1Na2SO4 electrolyte solution. Under UV-vis light irradiation, the results showed that Zn-In and W-Cd oxide photocatalysts gave a much higher photoactivity than Sn-doped Cd-In-Bi. Moreover, Zn-In and W-Cd oxide showed good visible light response for water oxidation to oxygen. At last, their incident photon-to-electron conversion efficiency (IPCE), band gap and band position were investigated in 0.2 mol·L^-1 NaOH solution.