利用多孔阳极氧化铝研究载体孔洞尺寸对负载银粒子团聚的影响

Study of Support Pore Size Dependence of Silver Particle Agglomeration by Applying Ordered Porous Anodic Alumina

利用阳极氧化方法制备了具有规整的可控孔洞尺寸的多孔Al2O3膜,并以此模拟实际的催化剂载体制备了负载银催化剂.采用扫描电镜、能量分散谱、透射电镜、X射线衍射和X射线光电子能谱等手段,研究了多孔阳极氧化铝的孔洞大小对负载的银粒子团聚的影响.结果表明,载体孔洞尺寸对银粒子团聚可能起到限制作用,而且这种限制作用随载体孔洞尺寸增大而减小.当载体的孔洞尺寸约为50nm时,随温度升高银粒子的团聚和生长都不明显;当载体的孔洞尺寸约为200nm时,随温度升高银粒子发生一定程度的团聚和生长,但孔洞尺寸的限制作用仍存在.这种载体尺寸的限制作用可以有效地阻止催化剂活性组分的团聚.

Ordered porous alumina films with a controllable pore size were fabricated by anodization and applied to simulate realistic catalyst supports. The support morphology dependence of the silver particle agglomeration on the Ag model catalyst loaded on this ordered porous anodic alumina was studied. Scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy were used to characterize the morphologies, compositions, and chemical properties of the model catalyst. When the average pore size of the alumina substrate is smaller than 50 nm, both the agglomeration and the growth of silver particles are suppressed greatly. But when the pore size is bigger than 200 nm, the agglomeration and growth of silver particles occur to some extent, while the confinement effect still exists. This confinement effect can efficiently prevent active components on catalysts from aggregation.