Studies On Photoelectrical Catalytic Hydrogen Generation Of CdS/TiO₂ Nanotubes

With the gradual depletion of fossil fuel and environmental pollution caused by fuel burning, hydrogen as an ideal clean energy sources has driven an increasing concern. Photocatalytic degradation of pollutants and hydrogen generation has provided a new way to alleviate the energy crisis and environmental problems. As the key to the photocatalytic technology, development of stable and efficient response to visible light catalytic material is a priority of this issue. CdS/TiO₂ nanotube electrode was fabricated by electrochemical anode oxidation and cathode reduction in this paper. We have achieved a good effect by using CdS/TiO₂ nanotube electrode to treat pollutants and generate hydrogen.CdS/TiO₂ nanotube electrode is a complex of CdS nanoparticles and TiO₂ nanotube array. TiO₂ nanotube arrays consist of nanotube layer, barrier layer, and titanium basement. The inner diameter of TiO₂ nanotube is 80-100 nm and the length is approximately 550 nm. TiO₂ is a mixed crystal phase with anatase and rutile phase after annealing at 550℃. The size of CdS particle is about 50 nm and the CdS is a mixed crystal phase with cubic and hexagonal phase.The absorption edge of CdS/TiO₂ nanotubes shows an obvious red-shift and the corresponding wavelength of absorption edge extends to 550 nm. The average photocurrent intensity of CdS/TiO₂ nanotubes electrode is approximately 424.9μA/ cm². The light conversion efficiency(Eeff) is calculated to be about 2.68%.Using Xe lamp as light source and 0.1 mol/L Na₂S as electro donors, photocatalytic hydrogen generation of CdS/TiO₂ nanotubes is about 1.23 ml in 2 hours. The photoelectrocatalytic hydrogen generation effect of CdS/TiO₂ nanotubes was also investigated. By optimizing conditions of bath voltage, pH values and the concentration of Na₂S, the photoelectrocatalytic hydrogen generation of CdS/TiO₂ nanotubes was more than 30 ml within 2 hours, which indicated that CdS/TiO₂ nanotubes electrode prepared in this experiment has high activity of photoelectrocatalytic hydrogen generation. The hydrogen generation activity of CdS/TiO₂ nanotubes used repeatedly for 5 times keeps higher, which indicates that catalyst has a better stability.Using acid orange 7 or methyl orange as the electron donors, CdS/TiO₂ nanotubes was used to photoelectrocatalytic degradation of dye and hydrogen generation. The results indicated that the dye as the electron donors has ability to capture the photogenerated holes, promote the separation of the photogenerated electrons and holes and enhance the efficiency of photoelectrocatalytic hydrongen generation.