纳米钯膜电极的制备、结构表征和特殊反应性能

Abstract

用循环伏安方法制备纳米钯膜电极,运用扫描隧道显微镜和原位红外光谱等方法研究其结构和反应性能.STM图像表明,制备的纳米钯膜具有特殊的层状结构,纳米级厚度的层状晶体由直径6nM左右的Pd微晶聚集而成.发现当钯膜厚度为几个纳米时,CO的吸附表现出异常红外效应,即红外谱峰反向和红外吸收显著增强(增强因子可达42.6).纳米钯膜电极对氢的反应也具有特殊的性能,与氢向钯晶格扩散吸收过程相比较,氢吸脱附的表面过程成为主要反应.研究结果还指出,纳米钯膜电极的异常红外效应和对氢反应的特殊性能与钯膜厚度密切关联,并可归结为钯膜材料的纳米尺度效应.

The Pd film nano materials supported on glassy carbon (nm Pd/GC) were prepared under conditions of electrochemical voltammetry.STM images illustrated that the Pd film consists of crystallites which are composed of nano particles of Pd with average size at around 6nm,and are of layer shapes.CO adsorption on nm Pd/GC electrodes manifested abnormal infrared effects (AIREs),i.e.,the inversion of IR band direction and the enhancement of IR absorption.In comparison with CO adsorption on massive Pd electrode,an enhancement factor at 42.6 was measured on a nm Pd/GC electrode of film thickness at 12.2nm.The nm Pd/GC electrode possesses particular properties for hydrogen reaction.It was revealed that,in contrast to hydrogen absorption by massive Pd electrode,the surface processes of hydrogen adsorption desorption become the dominant reaction on nm Pd/GC electrodes.The results demonstrated also that both the AIREs for CO adsorption and the particular properties for hydrogen reaction depend strongly on the thickness of Pd film,and can be consequently assigned to the nanometer size effect of Pd film materials.The present study has introduced important significance for further studies on surface electrochemistry and electrocatalysis.