Design And Control TiO₂ Composites Nano Array And Study On Their Photoelectrochemical Water Splitting Performance

In recent years,the energy crisis and environment problems are becoming even worse.Seeking for alternative to traditional fossil fuel,sustainable and clean new energy is extremely urgent.Solar energy is one of the inexhaustible energy,whose exploitation and application is a new research field.Photoeletrochemical?PEC?cells are effective means to realize the transformation and utilization of solar energy.PEC water splitting device can convert solar energy into chemical energy and store it in hydrogen bonds,and eventually produce clean and efficient hydrogen energy.Semiconductor materials are often worked as photoanode in PEC device due to their special optical properties and unique band structures.Noble metal nanoparticles can effectively extend the absorption spectrum and improve the absorption factor of semiconductor materials for their surface plasma resonance effect.In this paper,a series of photoanodes were fabricated of transition metal oxides semiconductor materials with structure conditioning or noble metal modified.Then the photoelectrochemical properties of those photoanode were studied to research the influence of structure on the properties.The main research contents are as follows:?1?One-dimensional TiO₂ nanorod array was directly grown on the conductive glass substrate via hydrothermal method.The reaction times and the acetic acid content in the reaction precursors can influence the morphology,structure and properties of TiO₂ photoanode.Then use the photoreduction method to fabricate Au modified TiO₂ photoanode.The content of Au nanoparticles was adjusted by different irradiation times.The principle of surface plasma resonance effect for improving photoelectrochemical properties of photoanode is also studied.When the irradiation time of light was 10 min,the content of Au reached 2.36 wt%.The photocurrent density of Au/TiO₂-10 min photoanode?1.1 mA/cm2 at 1 V vs Ag/AgCl?was about 3.5 times as much as it of pure TiO₂?0.32 mA/cm2 at 1 V vs Ag/AgCl?.Because the SPR of Au nanoparticles can extend the absorption spectrum to visible light,improve electron transport rate and promote the separation of photogenerated electronic-hole on the surface.?2?Three-dimensional branched TiO₂ nanorod array was directly grown on the conductive glass substrate via two-steps hydrothermal method.The temperature and time of the second reaction had great influence on the morphology and structure of the branches.Au modified 3D-TiO₂ photoanode was fabricated via photoreduction method.The content of Au nanoparticles was adjusted by different irradiation times.3D-TiO₂ photoanode had better absorption efficiency and inversion efficiency than 1D-TiO₂ photoanode,because the branches of 3D-TiO₂ could increase the reflection times of irradiated light.The biggest photocurrent density was reached 2.65 mA/cm2 at 1.23 V vs RHE by Au/3D-TiO₂-10 min photoanode,which was as much as 2.4 times of pure 3D-TiO₂ photoanode?1.09 mA/cm2 at 1.23 V vs RHE?and about 3 times of 1D-TiO₂ photoanode?0.88 mA/cm2 at 1.23 V vs RHE?.?3?Three-dimensional ZnO branched-TiO₂ nanorod array was grown on the conductive glass substrate via two-steps hydrothermal method and a seeded process.First 1D-TiO₂ nanorod array was directly grown on the conductive glass substrate.Then dipped into ZnO sol and annealed to form ZnO seeded TiO₂ substrate.Finally through the second hydrothermal process to fabricated ZnO/TiO₂ naorod film.The different concentration of reaction precursors and reaction times of the second hydrothermal process could greatly influence the size and morphology of the ZnO branches.The photocurrent density of ZnO/TiO₂ photoanode is 1.39 mA/cm2 at 1.0 V vs Ag/AgCl,which is about 4 times as much as photocurrent density of TiO₂ photoanode?0.32 mA/cm2 at 1.0 V vs Ag/AgCl?.It was bigger than 3D-TiO₂ photoanode,because the band structure of ZnO and TiO₂ are different and the conduct band of ZnO is higher than that of TiO₂ leading to fast photogenerated electronic transport from ZnO to TiO₂.