Study On The Preparation Of Sb, Ce Doped SnO₂ Photoanode And Their Photoelectrocatalytic Activity For Degradation Of Organic Matter In Water

Metal ions doped SnO₂ is a new photocatalyst that shows strong oxidation activity in the organic wastewater treatment.It has drawn many investigator's attention because it can decompose organic pollutants that in air and water into CO₂ and H₂O under UV illumination.But,up to now,the degradation of organic pollutants in water by photoelectrocatalysis has not reported.As semiconductor catalytic materials,SnO₂ need a bias potential in photocatalytic application because of its wide-band gap and low position of conduction band. The bias potential can take away the photo-electrons and decrease the simple combination of electron-holes,consequently,increase the photoefficiency evidently.In this paper,we prepared the Sb doped SnO₂ and Ce doped SnO₂ photoanodes,by making full use of its feature of high evolution oxygen potential,good conductivity and stability for photoelectrocatalytic degradation the pollutants in water,the research results can provide theoretical foundation for this kind new photoanode in practical applications. Using metal salts SnCl₄·5H₂O and SbCl₃ as precursors,Sb-doped SnO₂ photo-electrodes were prepared by the sol-gel and dip coating method.We characterized the Sb doped SnO₂ thin film by XRD and SEM.Results showed that the SnO₂ thin film electrode was rutile with tetragonal structure and its surface have density fragment structure and regular cheched surface.Those fragments increase the surface area of the film,and the area could increase the amount of the activated adsorption spots.Therefore,this fragment structure has advantage to the catalytic reaction.At the same time,the Ce-doped SnO₂ photo-electrodes were also prepared using metal salts SnCl₄·5H₂O and Ce(NO₃)₃·6H₂O as precursors.The Ce doped SnO₂ thin film was investigated by XRD,and we found it also have the rutile structure.Change the temperature have no effect to the crystal structure,but have great effect to the grain size and performance of photoelectrocatalysis.In this paper,the Sb doped SnO₂ electrode was used as the working electrode,the gas diffusion electrode was used as the counter electrode.A 250W UV lamp(365nm)was used as side light-source,phenol as the objective oragnic substance,the effects of different preparation conditions of doping amount,coating layers,calcined temperature on the photoelectrocatalytic performance of Sb doped SnO₂ electrode were investigated.The results showed that the Sb doped SnO₂ electrode which doped 6%of Sb(the mol ratio of Sb and Sn atom),calcined at 450℃,coating with 5 layers,had the highest photoelectrocatalytic activity.After 3.0h reaction, the degradation rate of phenol(50mg/L,50mL)is 99.8%and the removal of TOC is higher than 80%.The degradation rate of phenol in different processes including direct photolysis,photocatalysis,electrocatalysis and photoelectrocatalysis were compared in the same condations of operation,and the results showed that the photoelectrocatalysis is higher than the sum of photocatalysis and electrocatalysis.Phenol and methyl orange were employed as model organic pollutants,the effects of some factors such as initial pH value of solution,operated voltage and initial concentration on the photoelectrocatalytic degradation performance of Sb doped SnO₂ electrode were also investigated.The Ce doped SnO₂ electrode was used as the working electrode,the gas diffusion electrode was used as the counter electrode.We studied the effects of the doping amount and calcined temperature on photoelectrocatalytic performance.The results showed Ce doped SnO₂ electrode which doped 1.0% of Ce(the mol ratio of Ce and Sn atom),calcined at 500℃had preferable performance of photoelectrocatalysis.In 60 min,the degradation rate of phenol reach 74.8%by Ce doped SnO₂ thin film electrode,and its degradation rate is better than that of Sb doped SnO₂ thin film electrode(65.1%),but the stability of Ce doped SnO₂ electrode is not good as the Sb doped SnO₂.