P掺杂量对纳米TiO2结构及其光催化甘油水溶液制氢性能的影响

以钛酸丁酯为前驱体,以NaH2PO4为掺杂离子给体,采用溶胶-凝胶法制备了系列P掺杂的TiO2光催化剂,运用N2吸附-脱附、透射电子显微镜、X射线衍射、傅里叶变换红外吸收光谱、激光拉曼光谱、紫外-可见光漫反射等技术对催化剂进行了表征.结果表明,适量掺杂的P可以进入TiO2骨架中,而掺杂量过高时,P将溶解于TiO2晶格间隙中;P掺杂后的TiO2均为具有介孔结构的锐钛矿晶型纳米颗粒,其晶粒变小,分散度明显提高.适量P掺杂增大样品的比表面积,并使得TiO2禁带内引入杂质能级,降低了禁带能量,增加了光生电子和空穴的分离性能,提高了TiO2的吸光性能.光催化甘油水溶液制氢反应结果表明,P掺杂的TiO2表现出远高于纯TiO2的光催化活性;5%P掺杂样品在紫外光和模拟太阳光辐射下,其最高产氢速率可分别达1838和209μmol/(g.h).这与掺P后晶粒变小、比表面积增大、禁带能量降低以及光生电子和空穴的分离性能增加有关.

Effects of P Doping Amount on Structure and Photocatalytic Performance of TiO2 for H2 Production from Glycerol Solution

Using tetrabutyl-titanate and sodium dihydrogen phosphate as raw materials,TiO2 and P5+-doped TiO2 semiconductors were prepared by the sol-gel method.Their pore distribution,crystal structure,surface compositions,and photoabsorption properties were investigated by N2 adsorption-desorption,X-ray diffraction,Fourier transform infrared spectroscopy,FT-Raman,transmission electron microscopy and UV-Vis diffuse reflectance spectrum.The results show that P5+-doped TiO2 exists in nano-particles of anatase phase with mesoporous structure.P5+-doped TiO2 samples exhibit much smaller crystallite size and much higher specific surface area than pure TiO2.P-doped TiO2 samples show an extension of light absorption into the visible region,which mainly originates from the doping process with the formation of new energy level of P5+ between conductor band and valence band of TiO2 to reduce the energy gap and the electron-hole recombination rate.The P5+-doped TiO2 samples display improved photocatalytic activity for H2 production from glycerol solution,and 5% P5+-doped TiO2 shows a maximum H2 production rate of 1838 μmol/(g.h) under UV irradiation and 209 μmol/(g.h) under simulated-solar irradiation,respectively,which is related to the decrease of crystal particles,increase of specific surface area,and the reduce of the energy gap and the electron-hole recombination rate.