| TiO2 nanotube arrays prepared by electrochemical anodization have highly ordered tube structure,large specific surface area and many active sites,so they are widely used in the field of photoelectrocatalysis.However,as a wide band gap semiconductor,the utilization rate of solar energy in TiO2 is not high,so it is imperative to modify it in order to improve the photoelectric conversion efficiency.In this paper,TiO2 nanotube arrays were prepared on Ti substrate by electrochemical anodization method using titanium as titanium source.The effects of electrolyte system,anodizing times and annealing temperature on crystal structure,morphology and photoelectric response performance were investigated.TiO2 nanotube arrays were modified by N and WO3 binary modification to explore their effects on the photoelectrocatalytic performance of methylene blue.The results of this paper are as follows:（1）The titanium sheet reacted in the electrolyte with pure water/ethylene glycol/glycerol as solvent with ammonium fluoride as corrosion agent.The higher the viscosity of the electrolyte is,the slower the diffusion rate of fluoride ion is.The TiO2nanotube arrays formed in pure water are fragile at the top and difficult to fit with the titanium substrate at the bottom;the TiO2 nanotube arrays formed in ethylene glycol have a complete nanotube structure with smooth walls and long nanotubes;and the TiO2 nanotube arrays formed in glycerol are a porous structure and does not show the nanotubes.（2）The nanotube structure with more orderly arrangement was prepared by multiple anodization through the removal of oxide film.TiO2 nanotube arrays are classified as a double-layer structure of nanotubes in the upper and lower layers of nanopores,which has better photogenerated electron-hole separation ability,and photogenerated electrons and photogenerated holes move rapidly in the thin tube wall.（3）At appropriate temperature,the increase of annealing temperature is beneficial to the transformation from amorphous TiO2 to anatase phase,but if the temperature is too high,the anatase phase will transform into more stable rutile phase,and the anatase phase has the best catalytic performance.High content of anatase TiO2 can be prepared at 500℃.（4）The TiO2 nanotube arrays prepared by secondary anodization in ethylene glycol/ammonium fluoride electrolyte and annealed at 500℃have high photoelectric response ability and degradation efficiency of methylene blue,which are 48.5μA/cm2and 56.9%,respectively.When the WO3 recombination is carried out on this basis,the appropriate WO3 load is beneficial to the photoelectric response,but the excessive WO3 load will form a recombination center.The AMT solution with 10 m M/L as impregnation solution has the best performance,the photocurrent density can reach81.6μA/cm2,and the degradation efficiency of methylene blue is 81.9%.After N-doping by high temperature annealing under N2 protection,the N-TiO2/WO3composites can respond in the visible region,and the photoelectric response is obviously enhanced.The photocurrent density and degradation rate are 95.1μA/cm2and 89.5%,respectively.（5）The photoelectrocatalytic degradation of methylene blue by N-TiO2/WO3composite is significantly higher than the sum of electrocatalysis and photocatalysis,showing a good photocatalytic effect.（6）The applied voltage,the concentration of electrolyte and the initial concentration of methylene blue have certain influence on the catalytic effect.The best condition is 2 V applied voltage,0.1 mol/L Na2SO4 as electrolyte,and the initial concentration of methylene blue is 10 mg/L.In the kinetic analysis,it was found that all the materials were in accordance with the first-order kinetic equation,and after four cycle experiments,it was found that the material still maintained a high degradation effect,which could reach 75.4%. |
