SO2-4/CeO2-TiO2光催化材料的制备与光谱表征

采用溶胶-凝胶法结合硫酸浸渍法制备了SO2-4/CeO2-TiO2复合氧化物.利用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、吡啶吸附红外光谱(Py-FTIR)、紫外-可见光漫反射光谱(UV-Vis)、X射线光电子能谱价带谱(VB-XPS)及荧光光谱(PL)技术对样品的结构、性质进行了表征,以光催化分解水制氢为模型反应,评价了样品的光催化性能.XRD,FTIR结合PL结果表明CeO2与TiO2的复合形成了异质结构,有利于提高光生电子与光生空穴的分离效率,对催化剂活性的提高有促进作用;Py-FTIR谱图证明SO2-4/CeO2-TiO2复合氧化物在表面具有Lewis酸性,Lewis酸性位的产生是由于SO2-4在样品表面的配位吸附所致,S O— 的诱导效应增强了表面金属得电子能力,从而进一步提升光生载流子的分离效率;UV-Vis及XPS价带谱分析说明,半导体氧化物复合能够缩减带隙,拓宽光响应范围,Lewis酸性影响复合氧化物的能带结构,使其导带底位置向负向移动,利于光催化还原能力的提高,进而促进其光催化制氢活性.光催化分解水制氢实验结果表明,SO2-4/CeO2-TiO2复合氧化物具有优于纯氧化物CeO2,TiO2及未经硫酸浸渍的CeO2-TiO2复合氧化物的催化活性,5 h的产氢速率为1934.1μmol·g-1·h-1.光谱分析结果结合光催化制氢活性评价结果表明,SO2-4/CeO2-TiO2复合氧化物的异质结构与酸浸渍是影响样品光催化性能的主要因素.

Preparation and Spectral Characteristics of SO2-4 /CeO2-TiO2 Photocatalyst

SO2-4 /CeO2-TiO2 composite oxides were prepared with sol-gel and impregnation method.The struc-tures and properties of the as-prepared samples were characterized with X-ray diffraction (XRD),Fourier transform infrared spectroscopy (FTIR),pyridine adsorption infrared spectroscopy (Py-FTIR),UV-Vis dif-fuse reflectance spectroscopy (UV-Vis DRS),Valence band X-ray photoelectron spectroscopy (VB-XPS)and photo-luminescence(PL)spectroscopy.The photocatalytic activity of the samples was tested through the reac-tion of the hydrogen production from water splitting.The results of XRD and FTIR and PL revealed that the heterojunctions were formed into CeO2/TiO2 phase junctions,which was conducive to promoting the separa-tion of photo-generated electrons and holes.Py-FTIR spectra showed that Lewis acid site was formed on the surface of the SO2-4 /CeO2-TiO2 composite,while formation was attributed to the SO2-4 coordinated to metals on the sample surface.The induced effect of S O— led to an increase in the electron accepting ability of the surface metal ions and thereby further enhanced the separation of the photogenerated carriers.The UV-Vis and VB-XPS spectroscopy results showed that the semiconductor composites could narrow the bandgap and expend the light response range.The Lewis acidity affected the band structure of the composite oxide and made the position of conduction band minimum move to a more negative direction,which improved the photocatalytic re-ducibility of the catalyst and contributed to the improvement of hydrogen production activity.The results of hydrogen production from water splitting showed that the photocatalytic activity of SO2-4 /CeO2-TiO2 compos-ite oxide was better than that of pure CeO2 ,TiO2 and the CeO2-TiO2 composite oxide without the impregnation in sulfuric acid,and the average H 2 yield rate was 1934.1 μmol·g-1 ·h-1 in 5 h.The results of spectral a-nalysis combined with photocatalytic activity of hydrogen evolution showed that the synergetic effects of heter-ogeneous structure of SO2-4 /CeO2-TiO2 composite oxide and the acid impregnation promoted the photocatalyst activity.