Preparation Of N/TiO₂ Photoelectrodes By Anodic Oxidation And Its Photoelectrocatalytic Degradation Of Dyes

Currently,the environment faces two major challenges:environmental pollution and energy shortages.The solar photocatalytic technology can directly use sunlight to photocatalytic degradation of pollutants,which not only solves the problem of environmental pollution but also alleviates the predicament of energy shortage.Therefore,it is very important to prepare a highly efficient photocatalyst with solar photocatalytic ability.Among many photocatalytic materials,TiO₂ has been extensively studied for its advantages of being non-toxic,low-cost,and highly efficient.However,the large band gap and high photogenerated electron-hole recombination rate of TiO₂ result in low solar energy utilization and low quantum yield,which hinders the application of TiO₂ in actual production.The band gap of pure TiO₂ is 3.2 eV,which results in that it can only use UV light with wavelength less than 388 nm.In this paper,two kinds of N-doped TiO₂ photocatalytic materials were prepared by anodizing in ammonium nitrate electrolyte:N/TiO₂ thin film photoelectrode and N/TiO₂powder photocatalyst.By controlling and optimizing the preparation parameters,two kinds of photocatalytic materials had high solar photocatalytic performance,and could degrade the dye?Methyl Orange or Methylene Blue?wastewater in a short time under simulated sunlight.And these N/TiO₂ catalysts were characterized and analyzed by conventional characterization,such as SEM,XRD,XPS,UV-Vis,electrochemical workstation,spectroscopic ellipsometer?SE?.The following are the main results.?1?The optimum preparation conditions of N/TiO₂ thin film electrode were determined through single factor discussion and orthogonal analysis of electrolyte concentration,anodic oxidation voltage,oxidation time,calcination temperature and lasting time.The titanium sheet was anodized in 0.05 mol/L ammonium nitrate aqueous solution at 20 V for 4 min.After being cleaned and dried,it was calcined at 600?for 1 h in muffle furnace.Under this condition,the prepared TiO₂ thin film electrode contained0.28 at%substituted nitrogen.It was a mixture of anatase and rutile.The surface bulged with porous particles.Therefore,it not only absorbed UV but also visible light and near infrared light near 1045 nm,showed high photocatalytic performance under solar light.?2?TiO₂ thin film electrodes prepared under different oxidation conditions showed different apparent features?colors and surface particles?,and showed different photocatalytic properties.The formation mechanism of the color was determined by the optical effects on the surface.It absorbed visible light of a certain wavelength and showed the complementary color.It reflected visible light of a certain wavelength and showed the corresponding color of the reflected light wavelength.The interference between reflected light would cause differences in color brightness.The light scattered effect would make it gray.In addition,the surface optical effects also affected the photocatalytic efficiency of the photocatalyst,directly.It was found that the apparent features and photocatalytic properties were affected by the surface structure,thickness and surface optical effects of the thin film.These yellow TiO₂ thin film electrodes with small particles had higher photoelectrocatalytic performance than that of others.?3?N/TiO₂ powders were obtained by cleaning and drying the falling film fragments.The powder before calcination had porous structure and showed certain adsorption capacity.High-temperature calcination resulted in collapse of porous structure and transformation of crystalline structure,as a result that the calcined powder had no adsorption capacity but photocatalytic capacity.The N/TiO₂ powder calcined at 700?for2 h was a mixed crystal structure contained 0.49 at%substituted nitrogen,and its photocatalytic rate was the fastest.After 20 min photocatalytic degradation under simulated sunlight,the removal rate of 20 ml,20 mg/L Methyl Orange and Methylene Blue reached 83%and 95%respectively.