Study On Preparation And Properties Of RuO₂-load B/TiO₂ Nanotube Arrays

Titanium dioxide?TiO₂?is an important inorganic semiconductor material of n-type broadband gap,which has been widespread applications in many fields such as photocatalysis,gas sensor,air purification,self-clean materials,solar cells and other fields due its outstanding photocatalytic activity and environmental friendly features.Among various kinds of morphology,nanotubes have attracted special attention due to its high surface area,surface energy and adsorption capacity.However,wide band gap and easy ocurring of photogenerated electrons-holes of TiO₂ nanotubes cause the low utilization efficiency for visible light,which limits its applications in visible light region.In this research,our efforts are made to prepare B-dope and RuO₂ loaded TiO₂nanotube arrays by combining anodic oxidation with electrolytic and impregnation method.Microstructure,structure,surface chemical state and functional group are characterized by Field emission scanning electron microscope?FE-SEM?,energy dispersive spectroscopy?EDS?,transmission electron microscope?TEM?,X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?,UV-Vis absorption spectroscopy and Fourier transform infrared Spectrum techniques.Moreover,the photocatalytic degradation properties of methylene blue solution were investigated for all samples under visible light irradiation.The main research results are as follows:RuO₂ loaded TiO₂ nanotube arrays photocatalyst was fabricated by combining anodic oxidation with electrolytic method and impregnation method.Results reveal that under the applied 0.85 electrolyzedvoltage,Ru ion in the impregnating solution existed in form of+2 valence state.Only when the Ru³⁺was reduced to Ru²⁺in the impregnation solution,Ru element could be loaded onto the TiO₂ nanotubes surface and disperse uniformly in form of RuO₂ on the surface of TiO₂ nanotubes after the calcination.RuO₂/TiO₂ nanotubes were still characterized by the structure of unloaded TiO₂nanotubes,and the crystal structure was not changed by RuO₂ loading.The loading of RuO₂ will not increase the number of hydroxyl on the surface of TiO₂ nanotubes.In the0.0030 mol/L ruthenium chloride solution and under the 0.85 Velectrolytic voltage,RuO₂/TiO₂ nanotube arrays achieve the optimal photocatalytic activity,where The 2 h visible-light photocatalytic degradation rate of methylene blue was increased from37.50%for pure TiO₂ nanotubes to 66.67%for RuO₂/TiO₂ nanotube arrays.The enhanced photocatalytic activity of RuO₂/TiO₂ nanotube arrays could be attributed to the effective separation of photogenerated electrons and holes,which is related RuO₂captured the holes.B/TiO₂ nanotube arrays photocatalyst was fabricated by adding NaBF₄ in anodic oxidation process and its impacts of different quantity of NaBF₄ on the formation of nanotube are also investigated.Results indicate that B element could be incorporate into TiO₂ lattice and forms B-O-Ti bond,increasing the number of hydroxyl on the surface of TiO₂ nanotubes,reducing optical band gap,and causing the redshift of light absorption threshold value.When NaBF₄ optimum adding amount was fixed 0.6 wt%,B/TiO₂nanotube arrays photocatalyst achieve the optimal photocatalytic activity,where B ions concentrations and redshift of light absorption threshold value reached the maximum value of 2.24%and 412 nm respectively,the optical band gap reaches the minimum value of 3.01 and the 2 h visible-light photocatalytic degradation rate of methylene blue was increased from 37.50%for pure TiO₂ nanotubes to 75.15%for B/TiO₂ nanotube arrays.Via anodic oxidation methodby combined with electrolytic and impregnation methods,RuO₂-load B/TiO₂ nanotube arrays photocatalyst was fabricated by appropriating different contents of NaBF₄.Results showed that:RuO₂ easily deposited on the surface of B/TiO₂ nanotube and Ru element existed in form of RuO₂ and little RuO_x/Ru in RuO₂-load B/TiO₂ nanotube arrays where the formation amounts increase with the increasing B doping contents.The existence of RuO_x/Ru sharply reduces the contents of hydroxyl on the surface of nanotube.In comparison with the RuO₂-load or B-dope TiO₂ nanotube arrays,for RuO₂-load B/TiO₂ nanotube arrays,the band-gap energy increases and the blue shift of light absorption threshold valve occures.,which eventually induces the its equally or lower photocatalytic activity as pure nanotube.