The Study On The Construction And Photoelectric Conversion Properties Of TiO₂ Photoanode

With the rapid development of China’s industry,the demand for energy is increasing.Relying on international energy trade and importing energy from other countries is not conducive to economic internal circulation and industrial upgrading.Therefore,there is an urgent need to develop a green and sustainable energy source.Solar energy,as one of the natural resources that mankind depends on for survival,has attracted much attention because of its inexhaustible supply.Photoelectrochemical（PEC）water splitting technology is considered to be one of the most effective and clean solar energy conversion technologies.The photoelectrochemical water splitting process includes the oxidation of water on the photoanode to produce oxygen and the reduction of water on the counter electrode to produce hydrogen.The water oxidation process includes a continuous four-charge transfer reaction,which has a higher activation energy.Therefore,the water oxidation process on the anode is the main factor affecting water spliting.Significant results have been achieved in realizing efficient water splitting,through metal oxide semiconductor photoanodes such as TiO₂,Fe₂O₃,WO₃ and BiVO₄.TiO₂（rutile）has attracted people’s attention because of its low price,non-toxicity,wide application range,and strong light corrosion resistance.However,the PEC performance of TiO₂ is still subject to many limitations.For example,a wider band gap（3.0 e V）limits the generation of photo-generated carriers,a lower electron mobility(1 cm²v^-1s^-1),and a shorter space.Hole diffusion length（10～100 nm）.In this paper,a simple hydrothermal method is used to prepare a TiO₂ photoanode,and then the PEC performance of TiO₂ is improved by controlling the morphology,constructing a heterostructure,and loading catalysts.The main contents are as follows:1.Preparation,characterization and photoelectric conversion properties of Co-doped TiO₂ photoanode modified by nickel-iron double hydroxideThe in-situ cobalt-doped titanium dioxide photoanode（Co-TiO₂）was prepared by a simple one-step hydrothermal method,and then an ultra-thin nickel-iron double hydroxide layer（NiFe LDH）was electrodeposited as an oxygen release catalyst to obtain nickel-iron double hydroxide modified cobalt-doped titanium dioxide photoanode（NiFe LDH/Co-TiO₂）.The NiFe LDH/Co-TiO₂ photoanode has a photocurrent of 1.66 m A/cm² at 1.23 V vs.RHE,which is 1.66 times that of basic titanium dioxide.This is mainly due to the fact that cobalt doping effectively increases the concentration of carriers and enhances the electrical conductivity of the photoanode,while the electrodeposited nickel-iron double hydroxide can effectively reduce the electron-hole recombination and promote the surface oxygen evolution reaction.Furthermore,the photoelectrochemical performance of the titanium dioxide photoanode is significantly improved.2.Preparation,characterization and photoelectric conversion performance of NiOOH modified Al₂O₃ passivation branched TiO₂photoanodeThe titanium dioxide photoanode was prepared by hydrothermal method,and then branched titanium dioxide（B-TiO₂）and ultra-thin Al₂O₃ modified titanium dioxide（Al₂O₃/B-TiO₂）were obtained by immersion method,and finally NiOOH was electrodeposited to the surface of the branched titanium dioxide photoanode passivated by the ultra-thin Al₂O₃ layer to obtain NiOOH/Al₂O₃/B-TiO₂.The photocurrent of the NiOOH/Al₂O₃/B-TiO₂photoanode has a significant increase at 1.23 V vs.RHE,reaching 1.42m A/cm².Branched titanium dioxide has a larger specific surface area,which can effectively enhance light absorption and carrier transport.The ultra-thin Al₂O₃ passivation layer can reduce surface defects.Modified NiOOH can significantly improve the electron-hole transport efficiency of the electrode,thereby increasing the solar light-to-hydrogen conversion efficiency of the titanium dioxide photoanode.