Study On TiO₂ Nanotubes Based Photoelectrode With Enhanced Visible-Light Activity: Preparation And Properties

It has been well recognized that TiO₂ nanotube arrays (NTs) are of a promising material with application prospect in solar cells, dye-sensitized solar cells, biomedicine, environmental purification, photolysis water, and gas sensor , due to their unique chemical and physical properties. The precisely oriented nature of the crystalline (after annealing) nanotube arrays brings about excellent electron percolation pathways for vectorial charge transfer between interfaces。Considering what mentioned above, in the present work, ZnFe₂O₄,CdS,Pt,ZnFe₂O₄/CdS and Pt/CdS loaded TiO₂NTs were successfully prepared and characterized. Meanwhile, the photoelectrochemical activities were measured. Some key results were obtained as follows:(1) ZnFe₂O₄ and CdS nanoparticles were loaded onto TiO₂ nanotube (NT) layers formed on Ti-5Zr alloy. The ZnFe₂O₄ and CdS nanoparticles were obtained by h electrodeposition and chemistry bath deposition methods, respectively. Meanwhile, Fe/Zn ion ratio in the electrolyte determined the composition of Fe-Zn alloys, optimum electrodeposited Fe-Zn alloys for ZnFe₂O₄ formation were obtained by tuning the deposition variables. The prepared results indicated that the prepared samples were highly ordered TiO₂ nanotube composite with ZnFe₂O₄ and CdS nanoparticles loading on. We discussed the effect of depositing voltage and time on the morphology of ZnFe₂O₄ nanoparticles. The size of the CdS nanoparticles can be adjusted. The best process: Thiourea 1 mM, CdCl2 1 mM, pH adjusted to 9 by ammonia, deionized water 20 mL, 180 mL ethanol. The CdS-TiO₂NTs photoelectrode exhibited a higher photocurrent than pure TiO₂NTs.(2) The photoactivity of the Pt-TiO₂ photoelectrode depended on the amount of Pt namoparticles. When the loading amounts of Pt nanoparticles were appropriate, the photocurrent of the Pt-TiO₂ electrode was 2 times higher than the pure TiO₂ electrode. It was attributed to the enhanced separation ability of photogenerated electrons and holes. The photocurrent response of the CdS/Pt-TiO₂ electrode was 8 times higher than the pure TiO₂ electrode. It was attributed to the synergistic activity between the Pt,CdS nanoparticles and TiO₂NTs.