Investigation On Fabrication And Performance Of Multilayer Nanostructure Electrodes With Rare Earth Doped Tin Dioxide Based On The TiO₂ Nanotubes

The research and development of electrocatalytic electrode materials has always been the focus of electrochemical water treatment technology.The electrocatalytic activity and stability are the two most important parts of electrode,which are closely related to the preparation process and electrode structure.The thesis focused on the preparation and performance evaluation of doped Ti/TiO₂-NTs/SnO₂-Sb electrode,carrying out research on preparation,parameters optimization and structure characterization of electrodes.The influence mechanism of surface coating with nanoscale particulates on the performance of the electrode was discussed detaily.It also revealed how the TiO₂-NTs substrate architecture affected the electrocatalytic activity and stability of the Ti/TiO₂-NTs/SnO₂-Sb electrode.Moreover,the synergistic mechanism of the multiple components in coating of the Ti/TiO₂-NTs/SnO₂-Sb electrode doped by rare earth?RE?was revealed and a study of electrochemical depth treatment of phenolic wastewater was investigated.The process of solvothermal synthesis method for preparing multilayer nanostructure coating Ti/SnO₂-Sb electrodes was investigated and the optimal technical parameters were ascertained.The results showed that the multilayer nanostructure coating displayed a sphere-stacked cluster structure and the particle distribution was uniform and compact.Compared with the non-nanostructure coating electrode?106 nm?,the multilayer nanostructure coating electrode had much smaller grain sizes?23 nm?,which increased the activity site.Due to the uni que morphology and structure of coating,it possessed a higher oxygen evolution potential and a lower charge transfer resistance,and the percentage of adsorbed oxygen containing species(O_ads)was 1.74 times higher than that of non-nanostructure coating.Therefore,the kinetic rate constant of electrochemical degradation of phenol(16.3×10^–3/min)accelerated service life of electrode?16 h?were 1.72 times and 8.9 times higher than that of non-nanostructure coating electrode.TiO₂-NTs array layer was generated in situ on Ti substrate surface by anodic oxidation method,and the influence of growth conditions on the performance of TiO₂-NTs array layer was investigated.The results showed that anodic oxidation voltage,as the main influencing factor of TiO₂-NTs array layer morphology and surface hydrophilia,could regulate the electrode surface activity sites and the catalyst loading.The degradation rate of phenol and the service life of Ti/TiO₂-NTs/SnO₂-Sb electrode can be significantly improved by TiO₂-NTs array layer prepared under appropriate growth conditions?anodic oxidation voltage:25 V,anodic oxidation time:2 h?.The influence of Ce,Nd,Gd and Ho doping on the catalytic active,morphology,element composition,crystal structure and particle size of Ti/TiO₂-NTs/SnO₂-Sb electrode was analyzed.The optimum heat treatment temperature and rare earth doping amount of each modified electrode were determined.Taking phenol as model pollutant,the influence of heat treatment temperature and rare earth content on the electrocatalytic activity of four rare earths?Ce,Nd,Gd and Ho?doped Ti/TiO₂-NTs/SnO₂-Sb electrodes was investigated and the optimal preparation conditions were obtained.SEM tests showed that proper doping of RE could improve anode's morphology.The element analysis of the anodes were obtained using EDS,indicating that introducing RE could lead to the enrichment of Sb element to electrode surface from substrate,and the RE had a enrichment tendency towards electrode surface.Introduction of four RE restrained the upgrowth of SnO₂on grains in different extent.Taking Gd as representatives,the effect of RE doping on electrochemical phenol degradation process at Ti/TiO₂-NTs/SnO₂-Sb anode was studied.XPS,EPR and the generation ability of active radical test were employed to study the composition and chemical state of different elements and oxygen vacancy concentration on electrode's surface.The influence of rare earth doping on the surface structure and properties of SnO₂ composite electrode and the mechanism of multicomponent interaction in the electrode coating were discussed.Taking Gd doped Ti/TiO₂-NTs/SnO₂-Sb anode as representatives,the study of the electrochemical depth treatment of phenolic wastewater was carried out.Taking effluent COD as indications,the main factors affecting the treatment effect,including current density?12.5 mA/cm²?and degradation time?4 h?were investigated and determined.With the optimum operating parameters,total phenolic be completely removed.The COD decreased from 115 mg/L to 27.4 mg/L,which not only meets the industrial emission standards,but also meets the recycling requirements of enterprises.The TOC?decreased from 50.38 mg/L to 21.9 mg/L?and TN?decreased from 53.4 mg/L to 11.6 mg/L?in the wastewater showed a significant decline.The change of main organic material before and after depth treatment was analyzed by GC-MS,which indicated that this electrocatalytic oxidation system could obviously reduce the quantity of organic pollutants,indicating that the rare earth modified multilayer nano-structure composite electrode had comparative advantages in electrochemical depth treatment of low-concentration refractory organic pollutants.