负载银纳米粒子的多酸银盐复合材料的可见光催化性能研究

Polyoxometalate silver salts loaded with silver nanoparticles as new photocatalysts under visible light

通过固相研磨法,选取具有不同中心杂原子的Keggin型多酸(H_3PW_(12)O_(40)、H_4SiW_(12)O_(40)、K_5BW_(12)O_(40))固体与硝酸银固体反应,制备得到了系列低溶解度的多酸银盐前驱体(Ag_nPOM).再以这类多酸银盐为基质,通过紫外光照,使其中部分抗衡阳离子Ag^+原位还原生成金属Ag纳米粒子,进而可获得一系列具有不同Ag纳米粒子负载量的Ag_x^0/Ag_n^IPOM复合材料.固体漫反射光谱表明,Ag纳米粒子的表面等离子体(plasmon)共振吸收导致复合材料在可见光区域的吸收明显增加.这类复合材料在可见光照射下对光催化降解甲基橙和光还原Cr(Ⅵ)展现出高效、稳定的催化活性.随着阴离子所带电荷的增加,Ag纳米粒子的负载量明显增加,可见光吸收增强,因此光催化活性越高.Ag_x^0/Ag_5~IBW_(12)O_(40)展现最佳的光催化活性.

A series ofpolyoxometalate silver salts （Ag,POM） with low solubility were prepared by mechanically grinding the dry solid mixture of Keggin-type polyoxotungstates with different central heteroatoms and the silver nitrate. The as-prepared AgnPOM solids were further UV-irradiated, resulting in the generation of metallic silver nanoparticles （NPs） on the surface of the AgnPOM salts. Thus, a series of composite AgnPOM materials loaded with different amount of Ag NPs （Ag^0x/Ag^1nPOM） were obtained. The UV-Vis diffuse reflectance spectra show that the intensities of absorbing bands of the composite materials in visible area have been enhanced due to the plasmon resonance ofAg NPs. Such composite materials exhibit enhanced visible light-driven photocatalytic performances for dye degradation and the reduction of Cr（VI）. Furthermore, the loading amount of Ag NPs on the photocatalysts can be tuned by changing the negative charge of POM anions. As a result, the relevant photocatalytic activity of such composite materials can be also adjusted. Keywords： polyoxometalate, silver nanoparticles, solid grinding method, photocatalyst, visible light-driven