Preparation And Photoelectrochemical Performance Of TiO₂-based Nanostructured Photoanod

Developing renewable energy for sustainable development is increasingly important.Photoelectrochemical（PEC）water splitting to produce hydrogen by photoanode is a promising technology.Among the many semiconductor materials that can be used for PEC water splitting for hydrogen production,TiO₂ has received a lot of attention from researchers because of its non-toxic,stable properties and low cost.However,TiO₂ suffers from defects such as low optical energy utilization,high photogenerated carrier complexation chance,and slow hole transfer kinetics at the photoanode-electrolyte interface,which seriously restrict the further development of TiO₂.In this paper,TiO₂ nanorod arrays were synthesized by hydrothermal method as the substrate.A simple impregnation method was used to load Mg Al-layered double hydroxides（Mg Al-LDH）nanofilm on the surface of TiO₂ nanorods,and the composite photoanodes with core-shell structure were synthesized.The effects of impregnation time on the structure and photoelectric properties of TiO₂/Mg Al-LDH photoanodes were studied.The results show that the photovoltaic performance of TiO₂ nanorods loaded with Mg Al-LDH nanofilm is greatly enhanced compared with pure TiO₂,in which the photoanode TL8with 8 h impregnation time reaches a photocurrent density of 1.16 m A/cm² at 1.23 V（vs.RHE）,which is 116 times higher than that of the TiO₂ photoanode.The heterogeneous structure formed inside the TiO₂/Mg Al-LDH photoanode can effectively improve the separation efficiency of photogenerated carriers and ultimately enhance the photoelectrochemical performance of the film.TiO₂/Bi₂S₃ composite photoanodes were prepared by hydrothermal method.Bi₂S₃nanofilms with different morphologies were obtained by controlling the concentration of precursor solution.The effect of precursor concentration on Bi₂S₃ nanostructure was investigated and the growth mechanism of Bi₂S₃ nanofilms was proposed.Meanwhile,the photoelectric properties of TiO₂/Bi₂S₃ composite photoanodes with different morphologies were systematically investigated.The results show that the precursor solution concentration can affect the structural transition of Bi₂S₃ nanofilms from two-dimensional to three-dimensional to one-dimensional,in which the TiO₂/Bi₂S₃ photoanode（TBS2）with three-dimensional flower-like structure has the best photoelectrochemical performance,reaching a photocurrent density of 0.25 m A/cm² at 1.23 V（vs.RHE）,which is five times higher than that of the TiO₂ photoanode.Compared with the lower dimensional nanosheet and nanowire structures,the three-dimensional flower-like TiO₂/Bi₂S₃ nanostructures can not only improve the optical energy utilization of the electrodes,but also the heterogeneous structure formed inside them can effectively improve the interfacial charge transfer and separation of photogenerated carriers,and ultimately enhance the photoelectrochemical performance of the films.In this paper,TiO₂-based composite photoanodes with different dimensions of nanomaterials were prepared on TiO₂ nanorod arrays,and the effects of dimension and structure of nanomaterials on their photoelectrochemical properties and mechanism were systematically studied.