The Effect Of Vanadium Addition On The Photo Catalytic Performance Of TiO₂ Ceramic Coating Prepared By Micro-arc Oxidation

Photoanode is the key of photocatalysis technology,but at present,there are some problems in photoanode,such as poor binding of photocatalysis layer,small specific surface area,low photocatalytic efficiency of TiO₂ and so on.Multi-scale Ti-TiO₂ photoanode can be grown in situ on titanium substrate by micro-arc oxidation technology,but the photocatalytic efficiency of TiO₂ is still low.Based on this,in this paper,V-doped TiO₂ ceramic coating was prepared on TC4 titanium alloy by adding vanadate into the electrolyte and discussed the influence mechanism of V-element on the photocatalytic performancc of TiO₂ ceramic coating.The results are as follows:When the V addition amount was 12.60at%,the black ceramic coating dominated by amorphous TiO₂ can be formed.after annealing at 500?×1h,the Lab value of TiO₂ ceramic coating changed from 18.55 to 26.73,but it was still black,and the phases of the ceramic coating were mainly anatase and rutile TiO₂,with a small amount of V₂O₅.XPS analysis showed that the valence state of V element was not only V5+,but also V3+.Compared with the micro-arc oxidation TiO₂ ceramic coating,the absorption rate of V-TiO₂ ceramic coating was 95%in the UV-Vis region.The light wave response range expanded from ultraviolet region of 388.0nm to visible region of 733.7nm,therefore,it had good photocatalytic performance.Under the fluorescent light source of 400-760nm,the k value of V-TiO₂ ceramic coating was 0.06281 and t0.5 was 9.46,which was 14.67 times higher than that of TiO₂ ceramic coating.Under the UV light source of 200-400nm,the k value of V-TiO₂ ceramic coating was 0.1 1905 and t0.5 was 4.98,which was 4.37 times higher than that of TiO₂ ceramic coating.Under the xenon light source of 200-760nm,the k value of V-TiO₂ ceramic coating prepared on the foam titanium substrate was 0.32879 and t0.5 was 1.81,which was 1.23 times higher than the degradation rate of V-TiO₂ ceramic coating prepared on the smooth titanium substrate.When the V addition Ti-TiOw photoanode prepared on the foam titanium substrate was biased with 1.0v,the k value was 0.43877 and the t0.5 value was 0.91,which incrcascd the degradation rate of Ti-TiO₂ photoanode by 1.99 times compared with the V addition Ti-TiO₂ photoanode without bias.The mechanism of V addition to improve the photocatalysis of TiO₂ ceramic coating is as follows:V3+ replaced the position of Ti4+ in TiO₂ to form defective solid solution,the top position of the valence band of TiO₂ ceramic coating changed from 2.91eV to 1.41eV;the bottom position changed from-0.29ev to-0.28ev,thus reducing the forbidden band width of TiO₂ ceramic coating to 1.69 eV,to extend the absorbable wavelength to the visible light range,V5+formed TiO₂/V₂O₅ composite semiconductor with TiO₂ in the form of V₂O₅,In addition to TiO₂ semiconductor,V₂O₅ with conduction band?0.28ev?and valence band?3.00ev?also exists in the ceramic layer,so the photogenerated electrons with negative charge on TiO₂ migrated from the conduction band to V₂O₅ conduction band,while the photogenerated holes with positive charge on V₂O₅ migrated from the valence band to TiO₂ valence band,making the photogenerated electrons and holes on different semiconductors,effectively reducing the recombination of photogenerated electrons and holes,and improving the light quantum efficiency of V-TiO₂ ceramic coating.