Investigation On Photoelectrocatalytic Properties Of TiO₂ Nanotube Arrays Film-based Composite Materials

Converting solar energy into storable fuel has great significance to achieve CO₂ reduction targets,to get rid of reliance on fossil fuels and environmental protection.Using photoelectrocatalytic technology to conversion solar energy into hydrogen is one of feasible ways to solve the above problems.Building low-cost and high-efficiency photoelectrodes are the focus of current research.Titanium dioxide?TiO₂?-based photoelectrodes have been extensively studied due to abundant reserves,good chemical stability,and non-toxicity.Enhancing their optical and electrical properties and improving their photocatalytic activity are the focus of current research.In this work,TiO₂ nanotube arrays film?TiO₂ NTAs?was used to enhance its photoelectrochemical performance by loading carbon materials,noble metal nanoparticles,and narrow band-gap semiconductors.The main research contents and results are as follows:?1?First,the two-step anodic oxidization method was used to obtain the TiO₂ nanotube arrays film.Then,the carbon membrane?approximately 3 nm?on TiO₂ NTAs was coated by the hydrothermal method.The introduction of the carbon membrane can effectively expand the photoresponse range of TiO₂,and the carbon membrane can generate photo-generated carriers and inject to TiO₂ under irradiation due to its photosensitivity,which greatly increases the density of photo-generated electrons.The photocurrent density of the optimal sample?0.54 m A/cm²?was 3.9 times greater than that of pure TiO₂ NTAs?0.14 m A/cm²?under 300 W Xe lamp irradiation.Meanwhile,C/TiO₂ NTAs has higher carrier separation efficiency and lower carrier transmission impedance,indicating carbon membrane can effectively enhance the generation,separation and transmission of photo-generated carriers.?2?The carbon membrane and Au nanoparticles were combined to construct two different ternary nanostructures by hydrothermal and photochemical deposition processes over TiO₂ nanotube arrays film?TiO₂ NTAs?.One was carbon membrane bridged Au nanoparticles and TiO₂ nanotube arrays?Au/C/TiO₂ NTAs?,while the other was Au nanoparticles sandwiched between carbon membrane and TiO₂ nanotube arrays?C/Au/TiO₂ NTAs?.The two structures exhibited enhanced visible light harvesting ability,but they showed distinctly different photoelectric properties.Under the irradiation of the 300 W Xe lamp,the photocurrent density of Au/C/TiO₂ NTAs reached 0.984 m A/cm²,which was 3.74 times higher than that of C/Au/TiO₂ NTAs?0.263 m A/cm²?.By comparing and analyzing the lifetime of photogernerated electron and photoelectric response of the two samples,the mechanism of carriers separation and migration was revealed.In the C/Au/TiO₂ NTAs system,Au nanoparticles may become carriers recombination centers,which were related with much more reduction of the electron cloud density for Au nanoparticles and responsible for its poor photoelectrochemical performance.However,the multiple carriers transport paths make efficient utilization of the localized surface plasmon resonance effect of Au nanoparticles and the sensitization of carbon membrane in Au/C/TiO₂ NTAs,resulting in superior ability of photoelectrocatalytic water splitting.?3?Zn Se nanocrystal was deposited on the surface of C/TiO₂ NTAs by an in-situ growth method to construct Zn Se/C/TiO₂ NTAs system.The carbon membrane bridged Zn Se and TiO₂ composite showed enhanced visible light harvesting ability,and possessed the lowest charge carriers transfer resistance,the Rp resistance of Zn Se/C/TiO₂ NTAs?677.6 ??was lower than that of TiO₂ NTAs?6834 ??.The recombination of the photogenerated carriers of Zn Se/C/TiO₂ NTAs was also significantly reduced.Meanwhile,the ternary composite exhibited excellent H₂ evolution activity.The H2 evolution rate of Zn Se/C/TiO₂ NTAs?866.76 ?mol/cm²?was about 6.95 times higher than that of pure TiO₂ NTAs?124.64 ?mol/cm²?after 300 W Xe lamp irradiation for 200 min.The photoelectrochemical performance of Zn Se/C/TiO₂ NTAs clearly indicates the Zn Se and carbon membrane can increase the density of chage carriers,and the introduction of carbon membrane can greatly facilitate the separation and transmission of photo-generated carriers.