Preparation And Photoelectrochemical Performance Study Of High-energy Surface Exposed Titanium Dioxide Nanosheet Array Film

Titanium dioxide(TiO₂)is a photoelectric functional material with many excellent properties such as good stability,low cost,and good carrier transport performance.It is widely used in many green energy utilization and environmental protection fields such as photoelectrochemical solar cells,photocatalysis and optoelectronic devices.Related research pointed out that the different crystal faces of anatase TiO₂ have different surface states,which show different physical and chemical properties.Among them,the(001)crystal plane has high photoreactivity due to its relatively high surface energy,and has a good application prospect in photoelectrochemistry.In this paper,firstly by adjusting the concentration of hydrochloric acid in the precursor of the hydrothermal reaction,anatase phase TiO₂ nanosheet array film with the high-energy face(001)crystal face as the main exposed face was prepared,and the influence of adding different amounts of hydrochloric acid on its morphology was explored.,To study its growth mechanism.In order to further improve the photoelectric performance of the TiO₂ film,the continuous ion layer adsorption reaction(SILAR)method was used to sensitize it to CdS quantum dots to prepare a CdS/TiO₂ composite film,and its photoelectrochemical performance was studied.Finally,the photoelectrochemical performance of the CdS/TiO₂ composite film was improved by changing the deposition sequence of anion and cation and alkali treatment of TiO₂.This article is mainly divided into the following parts:1.Research on the controllable preparation and mechanism of TiO₂nano-films with different morphologies.The TiO₂ film was prepared on FTO by hydrothermal method,and the concentration of the reactant hydrochloric acid(HCl)was adjusted to explore the influence on the morphology of the TiO₂ nano-film.With the increasing concentration of HCl,the TiO₂ morphology gradually changed from spherical nanoparticles to angularity Obviously,until it evolves and grows into a TiO₂ nanosheet with a higher active surface(001)exposed.Through the analysis of morphology and crystal structure data,the process and principle of the morphology evolution of TiO₂ nanocrystals are obtained.They also tested their photoelectrochemical characteristics.Among them,the performance of the exposed TiO₂ nanosheet array film on the highly active surface(001)was the best,and the short-circuit current relative to the reference electrode was 0.114 m A cm^-2.2.Preparation of TiO₂ composite films with different morphologies sensitized by cadmium sulfide(CdS)quantum dots and their photoelectrochemical properties.Using TiO₂ nanostructures with different morphologies as the substrate,using cadmium nitrate(Cd(NO₃)₂·4H₂O)as the cadmium source,and sodium sulfide nonahydrate(Na₂S·9H₂O)as the sulfur source,the above-prepared TiO₂ film was CdS by the SILAR method.Quantum dot sensitization improves the photoelectrochemical performance of TiO₂nano-films.Among them,the CdS quantum dot-sensitized TiO₂ nano-sheet array film has the best performance,and the short-circuit current relative to the reference electrode is 2.25m A cm-2.,The relative increase of nearly 20 times before sensitization.3.The effect of anion and cation deposition sequence on the performance of CdS/TiO₂composite film.Taking the CdS quantum dot sensitized TiO₂ nanosheet array film as the research object,the sensitization sequence of two anions and cations was designed in the sensitization process of SILAR method,namely"sulfur followed by cadmium"and"cadmium followed by sulfur".Experimental data shows that the sensitization sequence does not change the crystal structure,but has a great influence on the deposition amount of CdS quantum dots.The performance of the CdS(S-Cd)7c/TiO₂photoanode prepared by sulphur first and then cadmium is significantly better than the CdS(Cd-S)7c/TiO₂photoanode prepared by cadmium first and then sulfur.The short-circuit current density of the former relative to the reference electrode is 4.5 m A cm^-2,which is twice the photocurrent density of the latter.4.The effect of alkali treatment of TiO₂ on the performance of CdS/TiO₂ composite film.The TiO₂ nanosheet film is immersed in a 0.1 M sodium hydroxide(Na OH)aqueous solution at a constant temperature of 30?for different time(0h?0.5h,1h,1.5h),and then subjected to CdS quantum dot sensitization(first cadmium and then sulfur)),and study the photoelectric properties of the obtained composite film.The data shows that alkali treatment increases the oxygen vacancies on the TiO₂ surface,which is beneficial to the growth of CdS quantum dots.Therefore,the performance of the composite film after alkali treatment is better than that of the TiO₂composite film without alkali treatment.Moreover,with the prolongation of the alkali treatment time,the photoelectric performance showed a rule of first increasing and then decreasing.When the alkali treatment was carried out for 1hour,the performance of the obtained photoanode was the best,and the current density reached 5.25 m A cm^-2,which was not alkali-free.2.3 times of the processed TiO₂composite film.5.Combining the advantages of the deposition sequence and alkali treatment of TiO₂,the TiO₂ after alkali treatment is sensitized with CdS quantum dots.The data shows that after alkali treatment for 1 hour,the order of sulfur followed by cadmium is used for CdS sensitization.The photocurrent density of the sample CdS(S-Cd)7c/TiO₂(1h)reaches the maximum value in the series of experiments in this paper,which is 6m A cm^-2.It shows that the alkali treatment on the oxide surface modification and the sensitization sequence change have a great influence on the performance of the quantum dot sensitized composite film prepared by the SILAR method.