可见光下高催化活性不同结构Sr/TiO_2催化剂的制备和表征

Preparation and Characterization of Sr/TiO_2Catalysts with Different Structures and High Photocatalytic Activity under Visible Light

采用分步沉积法制备不同Sr/Ti摩尔比例的Sr/Ti O2催化剂,以X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、傅里叶变换红外(FT-IR)光谱、紫外-可见漫反射光谱(UV-Vis RDS)等手段对样品进行了表征,以可见光催化降解亚甲基蓝为模型反应考察样品光催化活性.结果表明,催化剂的活性和结构随Sr/Ti摩尔比(n(Sr)/n(Ti))的变化而变化,当n(Sr)/n(Ti)≤3/2时,催化剂呈由Ti O2和Sr Ti O3组成的球状结构;而当n(Sr)/n(Ti)在3/2与4/1之间时,催化剂呈片状结构,且随着n(Sr)/n(Ti)增大,催化剂组成由Sr Ti O3和Sr2Ti O4变为Sr2Ti O4和Sr(OH)2H2O;当n(Sr)/n(Ti)=9/1时,催化剂呈以Sr(OH)2H2O为主的针状结构.其中,n(Sr)/n(Ti)=4/1的样品表现出最高的光催化活性,一级反应速率为Sr Ti O3钙钛矿催化剂的5.0倍,商用P25的86.7倍.

Sr/TiO2 catalysts with different Sr/Ti molar ratios （n（Sr）/n（Ti）） were synthesized by fractional precipitation. The samples were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, Fourier transform infrared （FT-IR） spectrometry, and ultraviolet-visible diffuse reflectance spectrophotometry （UV-Vis RDS）. The photocatalytic activity of the samples under visible light was determined using the photocatalytic degradation of methylene blue. The photocatalytic activities and structures of the catalysts changed with n（Sr）/n（Ti） molar ratio. When n（Sr）/n（Ti）≤3/2, the catalysts, which were composed of TiO2 and SrTiO3, showed a globular structure. When n（Sr）/n（Ti） was between 3/2 and 4/1, the catalysts had a flaky structure. As the n（Sr）/n（Ti） increased, the composition of the catalysts changed from SrTiO3 and Sr2TiO4 to Sr2TiO4 and Sr（OH）2？H2O. When the n（Sr）/n（Ti） ratio was 9/1, the catalyst mainly consisted of Sr（OH）2？H2O and exhibited an acicular structure. The sample with n（Sr）/n（Ti）=4/1 exhibited the highest photocatalytic activity;its first-order reaction rate constant was 5.0 times as high as that of the perovskite catalyst SrTiO3 and 86.7 times as high as that of the commercial Ti photocatalyst P25.