Preparation And Photocatalytic Performance Of Metal Ion And Non-metal Ion Co-doped TiO₂Film Electrodes Under Visible Light

This paper on how to prepare high stability and high photocatalytic activity ofimmobilized TiO2films electrodes and expand the light absorption from ultraviolet light tovisible light of the TiO2in the photocatalytic activity, to improve the ability of TiO2catalystresponse to visible light, LaxNy/TiO2/Ni and CuxNy/TiO2/Ti films electrodes were preparedand determined the best prepare technology. Immobilized TiO2onto the different substratesand choosing different techniques are used to various types of wastewater and improved theapplication of TiO2flm electrode in photoeletrocatalysis technology.La/N co-doped TiO2flm electrodes on Ni substrates were successfully prepared bysol-gel method and dip-coating method with the goal of enhancing the photoelectrocatalyticactivity under visible light. The morphology and composition of the La/N co-doped filmswere characterized using scanning electronmicroscopy (SEM), X-ray diffraction (XRD), andUV–Vis diffusion refection spectroscopy (UV–Vis DRS). The photocatalytic activities of theLa/N co-doped TiO2film electrodes were evaluated by the degradation of Malachite Green.The visible light photocatalytic degradation of Malachite Green (MG) was tested and La/Nco-doped TiO2flm electrodes showed the highest degradation efficiency up to82.6%afterthe treatment. It showed that La3+and NH4+co-doped TiO2flm significantly improves thephotocatalytic efficiency under the visible light. When+4.0V anodic bias potential andvisible light were simultaneously applied, the degradation effciency of Malachite Green overthe La/N co–doped TiO2flm electrodes was signifcantly improved.Malachite Green photoelectron-oxidation degradation was kinetically investigated in aphotoelectrocatalytic reactor, using LaxNy/TiO2/Ni film electrodes as the electrode which wasprepared by sol-gel method and dip-coating method. Results indicated that reaction rate andremoval efficiency were strongly depended on initial Malachite Green concentration, initialpotential bias, initial pH, and reaction temperature. The kinetic equation for Malachite Greenphotoelectron-oxidation under the conditions of10~50mgL-1of initial Malachite Green,3.0~9.0of pH,1-7V of potential bias,288~328K of temperature could be described using thechemical kinetics, which was fitted well with the experimental data, with average activation energy Ea=10.895×103J·mol-1. The reaction order of initial pH (1.595) is higher than that ofinitial concentration (0.462) and potential bias (0.953), which indicates that thephotoelectron-oxidation rate can be controlled efficiently through adjusted initial pH. Theexperiments demonstrated that initial pH would approach its statured value with increasinginitial pH.Cu/N co-doped TiO2flms on Ti substrates were successfully prepared byelectrochemical method with the goal of enhancing the photoelectrocatalytic activity undervisible light. The morphology and composition of the Cu/N co-doped films werecharacterized using feld emission scanning electronmicroscopy (FE-SEM), X-ray diffraction(XRD), energy dispersive X-ray (EDX), and UV–Vis diffusion refection spectroscopy(UV–Vis DRS). The photocatalytic activities of the Cu/N co-doped TiO2films were evaluatedby the degradation of humic acid. The visible light photocatalytic degradation of humic acid(HA) was tested and Cu/N co-doped TiO2flms showed the highest degradation efficiency upto41.5%after210minutes treatment. It showed that Cu2+and NH4+co-doped TiO2flmsignificantly improves the photocatalytic efficiency under the visible light. When+5.0Vanodic bias potential and visible light were simultaneously applied, the degradation effciencyof HA over the Cu/N co–doped TiO2flms was signifcantly improved to93.5%after210minutes treatment.Landfill leachate rejected by reverse osmosis (RO) oxidation degradation was kineticallyinvestigated in a photoelectrocatalytic reactor, using Cu-N co-doped TiO2/Ti photocatalyst asthe electrode which was prepared by anodized oxidation method. Results indicated thatreaction rate and removal efficiency were strongly depended on initial landfill leachateconcentration, initial potential bias, initial pH, and reaction temperature. The kinetic equationfor landfill leachate oxidation under the conditions of876~4378mgL-1of initial landfillleachate COD,2.0~8.0of pH,5-23V of potential bias,283~323K of temperature could bedescribed using the chemical kinetics, which was fitted well with the experimental data(R2=0.967~0.998), with average activation energy Ea=6.35×104J·mol-1. The reaction order ofinitial concentration (1.326) is higher than that of potential bias (1.102) and pH (0.074),which indicates that the oxidation rate can be controlled efficiently through adjusted initial concentration. The experiments demonstrated that potential bias would approach its staturedvalue with increasing potential bias.Using density function theory (DFT), the geometry, band structure and electronic densitystates of La0.25N co-doped TiO2、Cu0.0625doped TiO2; Cu0.125doped TiO2and Cu0.0625Nco-doped anatase titanium dioxides were studied at plane wave ultra-soft-pseudo-potential(PWPP) level. The conduction bands involve N-2p and Ti-3d electrons, and value bandsinclude O-2p and Cu-3d electrons in Cu/N-TiO2. The forbidden band becomes narrower, andthe Fermi energy becomes lower at the same time. It may lead us to the conclusion that thereshould be a red shift of the absorption band to enhance the visible-light photocatalytic activityof TiO2with the adulteration of La, Cu and N.