Study On The Relationship Between Photoconductivity And Photocatalytic Performance Of TiO₂Films

TiO2has always been a research hotspot as a photocatalysis, while the complexity makes the performance hard to evaluate. Photoconductivity and photocatalysis are both related with photo-generated carriers.Phase composition, crystallite size, film thickness and ion doping influence photocatalysis, in order to make sure the integrity of samples for experiments, we prepared TiO2films with holding time, film thickness, annealing temperature and F-doping ratio on quartz glass by sol-gel spin-coating method. We used these samples to investigate the relationship between photoconductivity (Δσ) and photocatalysis (kapp) under UV365nm.The results showed that photocatalytic activity was better with higher photoconductivity, indicating there was some inherent relationship between photoconductivity and photocatalysis, providing experimental basis for the physical characterization of photocatalysis. The crystallite size was improved by increasing holding time, with greater Δσ and kapp kapp, kapp increased and then decreased with the increase in thickness of TiO2layer, its optimum value was331.5nm. Different annealing temperatures generated various TiO2crystal structures, rutile-anatase mixed phase (750℃) showed the best two properties, the600℃one with pure anatase was better than the550℃one, while the pure rutile (900℃) showed the worst, the sample annealed at400℃with amorphous structure showed no photoconductivity and photocatalysis at all. As for F-doping ratio, Δσ, kapp increased and then decreased with the increase F doped in TiO2layer, its optimum value was2%.To explore the inherent relationship between Δσ and kapp, we applied catalytic kinetic method and photo-generated holes were main oxidants in photocatalysis, proposed some assumptions, making the model for analyzing the mechanism more simple, acquired quantitative equation of Δσ-kapp. By plotting with (Δσ, kapp) under different light intensity of the same sample, applying the quantitative equation of Δσ-kapp as model, finding that a, b reflected the variation trend of Δσ-kapp. a, b illustrated photocatalysis was mainly affected by the carriers and adsorption characteristic on the surface.