Photoelectric Properties And Band Modulation Of The Materials Based TiO₂ By Theoretical And Experimental Method

Here we explore the photoelectric properties and Band modulation of the materials based TiO2 by theoretical and experimental method in-depth. Firstly, we improve both the method, hydrothermal method and sol-gel method, to prepare TiO2 anatase phase. Anatase-to-rutile phase transition temperature of TiO2 is 750? to 850? confirmed by XRD. Then, we prepared non-metallic doped TiO2 by hydrothermal method and found that the annealing step can promote the crystallization of samples. However, the catalytic properties were not well. And we found that the I doped TiO2 showed strong catalytic ability, of which the catalytic rate can reach more than 80% for methyl orange in 30 min. The third step, we prepared rare earth elements doped TiO2 by solvent hot method and found that the rare earth ions inhibited the phase transformation and grain growth, which result in a decrease of grain size and a increase of the specific surface area, which significantly improve catalytic activity. Doped double degradation efficiency is superior to the single rare earth ions doped samples, the catalytic rate of doping TiO2 with 0.5 %La+0.5% Y reached 85.94% for methyl orange in 30 min. The fourth Step, the S2-, Fe3+ doped TiO2 were prepared by hydrothermal method, the synergy of metal and nonmetal elements were studied, we found that the particle size decreases, and the critical value of visible wavelength changed from near 387 nm to 400 nm, which suggests a decrease of the energy gap after doping. TiO2 with doped S and Fe can get further improvement for the degradation of methyl orange rate. Step 5, Pure_TiO2, N/Fe_TiO2, N/Fe /La_TiO2 powder material were prepared by sol-gel method, XRD shows the samples all were anatase phase, but the ionic lattice distortion is added and a smaller particles, and photoluminescence peak moved to 425 nm, energy gap decreases, which further proof that the synergy of N element and other metallic elements. And we fouhd the N/Fe/La_TiO2 photocatalytic degradation ability measured stronger than N/Fe TiO2.The complex energy level of 4f electronic structure of rare earth elements can further enhance the catalytic ability of TiO2.Step 6, the first-principles is used for calculation the crystal structure and electronic structure of the doped TiO2, we found that a distortion of doping TiO2 crystal lattice, the impurities result in electron orbital hybridization between the conduction band and valence band form the impurity level and reduce the width of the band gap of TiO2. the light absorption curve moved to the visible light region, which raising the utilization ratio of visible light and increasing the impurity level state density peak located on the top of the valence band of the TiO2 obviously and also increasing the electron transition probability, improving utilization of solar energy. To explains the reason of improving catalytic ability theoretically.