SiO_2担载的CuO_x纳米粒子量子尺寸效应的红外光谱研究

FTIR Spectroscopy Study on Quantum Size Effect of CuO_x Nanoparticles in CuO_x/SiO_2

以硝酸铜作为前驱体,利用尿素作为沉淀剂,采用均相沉积沉淀方法合成了具有纳米尺寸CuOx的CuOx/SiO2材料,并通过改变样品的焙烧温度,得到了一系列具有不同纳米尺寸CuOx的CuOx/SiO2材料.采用TEM和原位红外光谱技术对CuOx纳米粒子的形貌、尺寸以及CO吸附性能进行了表征.结果表明,随着样品焙烧温度的升高,球形CuOx纳米粒子逐渐聚集,其尺寸从3 nm增加到11 nm,CO在CuOx上吸附的红外峰峰强逐渐减弱,并且红外频率从2135 cm-1红移到了2120 cm-1.研究结果表明,随着CuOx纳米粒子尺寸的增加,吸附中心Cuδ+离子的正电荷密度逐渐减小,导致Cuδ+离子与CO分子之间的电场相互作用变弱,使得CO分子在Cuδ+离子上吸附的红外频率发生了红移.说明在这个纳米尺寸范围内,CuOx纳米粒子具有明显的量子尺寸效应,不同尺寸的CuOx纳米粒子,其电子结构性质明显不同.

The nanosized CuOx/SiO2 catalysts were prepared by homogeneous deposition method with urea as the deposition reagent.The sizes of CuOx nanoparticles were adjusted by changing calcination temperatures of CuOx/SiO2 samples.The size and morphology of CuOx nanoparticles were characterized by TEM,and the adsorption behavior of CO on CuOx nanoparticles was also studied by FTIR spectroscopy.With increasing the sizes of the spherical CuOx nanoparticles from 3 nm to 11 nm,the intensities of IR bands of adsorbed CO on Cu＋ ions are gradually decreased,and the frequencies of adsorbed CO are also red shifted from 2135 cm-1 to 2120 cm-1.It shows that the electronic properties of Cuδ＋ are changed with increasing the sizes of CuOx nanoparticles,namely,the quantum size effect controls CO adsorption on CuOx nanoparticles.