Preparation And Photoelectrochemical Properties Of Blackened TiO₂/B-BTO/CdS Ferroelectric Composite Film By Al-reduction

In this world,energy crisis intensifies,seeking sustainable clean energy has become an urgent problem to be solved.Hydrogen production by photoelectrochemical（PEC）water splitting has become an effective method to exploit and utilize solar energy.The design of semiconductor photoelectrode with excellent performance is the key to hydrogen production by PEC.It is an effective way to enhance the PEC performance of photoanode by improving the utilization rate of light and promoting the efficient carrier separation.In this paper,TiO₂/B-BTO/Cd S photoelectrode was prepared successfully based on the good PEC performance of TiO₂ semiconductor,the unique spontaneous polarization of Ba TiO₃（BTO）and the excellent light absorption capacity of Cd S.The spontaneous polarization field of BTO improved the interfacial carrier separation,and the oxygen vacancy generated by Al-reduction enhanced the visible light absorption of TiO₂/B-BTO.By depositing Cd S nanoparticles,the photoresponse of TiO₂/B-BTO/Cd S can be significantly enhanced in the visible region.The synergistic effect significantly enhanced the PEC performance of the TiO₂/B-BTO/Cd S photoelectrode.The effects of Al-reduction temperature and Cd S loading on optical and PEC properties of the samples were systematically studied.The specific research content is as follows:（1）The blackened TiO₂/TiO_2-x nanorod arrays were successfully fabricated by combining the hydrothermal route and Al-reduction method.The effect of Al-reduction temperature on the structure morphology,optical and PEC properties of blackened TiO₂/TiO_2-x nanoarray was studied.The results showed that Al-reduction was a secure-safe and effective method to improve the PEC performance for semiconductor.After Al-reduction,the light absorption of oxygen-deficient TiO₂/TiO_2-x was enhanced to the visible region.Without bias voltage,TiO₂/TiO_2-x photocurrent density reached the maximum at 350℃Al-reduction temperature,which was 9.9 times of pure TiO₂（2）TiO₂/BTO nanoarrays were prepared by secondary hydrothermal method using TiO₂nanoarray as precursor.The blackened TiO₂/B-BTO nanoarrays were regulated by Al-reduction method at different reduction temperatures.The crystal structure and surface valence state of the samples were confirmed by X-ray diffraction,scanning electron microscopy and X-ray energy dispersion spectroscopy.The photoelectrochemical test of the photoelectrode was carried out using an electrochemical workstation.The results showed that the TiO₂/BTO photocurrent was improved by the spontaneous polarization field of BTO,and the formation of oxygen vacancy in BTO caused by Al-reduction enhanced the visible light absorption of TiO₂/B-BTO,thus improving the photoelectrochemical properties of TiO₂/B-BTO.The photocurrent density of TiO₂/B-BTO at 400℃reached the maximum（0.84 mA/cm²）,which was 4.2 times that of TiO₂/BTO.（3）TiO₂/B-BTO/CdS composite films were prepared by chemical bath deposition on the basis of optimal TiO₂/B-BTO sample.The loading of Cd S was regulated by different deposition times.The morphology and light absorption of the samples were tested by scanning electron microscopy,UV-vis and other characterization instruments.The results showed that the optical response range of TiO₂/B-BTO/Cd S was greatly broadened than that of TiO₂/B-BTO.The photoelectrochemical test of the photoelectrode with different deposition times was carried out under unbiased voltage.TiO₂/B-BTO/Cd S-5 was up to 7.14 m A/cm²,which is 8.5 times higher than that of TiO₂/B-BTO and 2.2 times higher than that of pure Cd S-5.The effective separation and transfer of charge carriers and the broadening of the photoresponse range were responsible for the significant improvement of the PEC performance of TiO₂/B-BTO/CdS-5.