火焰辅助热解方法制备Ag_2O/TiO_2及其光催化制氢性能

Facile Synthesis and Photocatalytic Activity for Hydrogen Evolution of Ag_2O/TiO_2

以钛酸丁酯和硝酸银为前驱体,采用一步火焰辅助热解法制备了Ag_2O/TiO_2光催化剂并研究了样品在紫外-可见光照射下的光催化制氢性能。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis DRS)对样品进行了表征。XRD结果表明TiO_2均为锐钛矿晶型,Ag的引入对XRD结果无明显影响。SEM图显示未修饰的TiO_2是微球形貌,随着引入Ag含量的增加,微球减少直至消失。通过XPS分析和化学沉淀法表明样品中Ag的存在形式为Ag_2O。UV-Vis DRS测试发现引入Ag后提高了样品的光吸收。前驱体中Ag的量影响样品的光催化活性,最高的光催化制氢的活性可以达到相同条件下的P25的15倍。对光催化反应后的样品进行分析,认为在光催化过程中部分Ag_2O通过光生电子转化为Ag形成Ag/TiO_2,进一步提高光催化制氢活性。

The AgzO/TiO2 composite was synthesized via a facile flame thermal method using tetrabutyl orthotitanate and AgNO3 as precursors. The samples were characterized with X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS）, ultraviolet- visible diffuse reflectance spectroscope （UV-Vis DRS） and photoeatalytic hydrogen evolution under UV-Vis light irradiation. XRD results showed that anatase TiO2 was obtained directly and no obvious effect on the crystal structure was observed with the introduction of desired amount of Ag. SEM images show microspherical morphology for the as-synthesized samples without Ag and irregular morphology for those with higher content of Ag. XPS and chemical precipitation method results indicated that Ag existed in the forms of Ag20 in the resulted samples. UV-Vis DRS showed that the introduction of Ag could enhance light absorption. The highest photocatalytic hydrogen generation rate of sample was about 15 times as high as that of P25. The sample after photocatalytie reaction was chemically analyzed and it is assumed that the Ag20 was partly photoreduced to Ag, which further benefits the photocatalytic hydrogen production from Ag/TiO2 heterostructures.