Preparation And Photocatalysis Properties Of Nonmetal Self-doping （C,S）-TiO₂

With the rapid progress of science and technology, energy andenvironmental pollution problems are becoming increasingly severe.Photocatalysis has attracted great attention due to its potentialapplications in pollutant degradation and solar fuel production. TiO2has been most frequently employed as the photocatalyst owing to itslow cost, nontoxicity, and high stability. However, TiO2becomesactive only under ultraviolet light irradiation because of its large bandgap (anatase3.2eV, rutile3.0eV), which limits its applications forsolar energy harvesting. In order to improve its photoreactivity and toextend the absorption edge into the visible-light region, Nonmetalself-doping (C, S)-TiO2were prepared by sintering and hydrothermalmethods. XRD, XPS, BET, Raman, SEM, TEM and UV-vis were appliedto characterize the crystallinity, elements combined state, surfaceareas, optical property, surface structure morphology and thephotocatalytic degradation was also analyzed. Moreover, the different reaction mechanisms were revealed based on themicrostructure analysis. The results are as follows:(1) TiS2and TiC were chosen as the precursor to synthesizenonmetal S-TiO2and C-TiO2by heating TiS2and TiC separately in air.The best preparation conditions are also discussed. Thephotodegradation of rhodamine B was studied. It can be concludedthat the photodegradation ratio of the samples prepared by sinteringmethod can be achieved to about60%. However, the hightemperature is not favorable to retain dopant atoms in the TiO2lattice.Moreover, uniform doping is not easy to obtain under this reactionconditions.(2) Hydrothermal oxidation of TiS2and TiC were used to obtainnonmetal S-TiO2due to the lower temperature advantage ofhydrothermal reaction. On one hand, lower reaction temperature canprovide a mild condition to retain much higher doping concentrationin TiO2during the oxidation process. On the other hand, the synthesisis more environmentally friendly than other methods mentionedbecause it is unnecessary to introduce a new precursor as dopingsource. Therefore, it is a simple and effective approach to obtainnonmetal S-TiO2with S substituting O sites. According to thecharacterization, it can be concluded that the high crystalline TiO2nanoparticles were formed at a low temperature without further calcination at high temperature. Comparing with other lowtemperature preparation method, this method was simple and theexpensive equipment was no necessary. It can be concluded that thephotodegradation ratio of the hydrothermal method preparedsamples to rhodamine B can achieved about80%. Comparing withother TiO2catalyst prepared in different methods, it showed higherphotocatalytic activity.(3) Hydrothermal oxidation of TiC was used to obtain nonmetalC-TiO2. Formation of the hollow core ball structure has the largerspecific surface area, which makes the photocatalytic reaction morefully. It can be concluded that the photodegradation ratio of thehydrothermal method prepared samples to rhodamine B can achievedabout60%. Comparing with other TiO2catalyst prepared in differentmethods, it showed higher photocatalytic activity.In conclusion, we realized the preparation of nonmetal dopingS-TiO2and C-TiO2nanocatalyst with higher photocatalytic activity bythe sintering process and hydrothermal method. The research resultshave the vital significance to other semiconductor oxide doping infield of photocatalysis and bandgap engineering.