酸性溶液中Rh电极上CO孪生吸附态的FTIRS研究

FTIS Observation of Twin Adsorbates of CO on Rh Electrode in Acid Solution

采用现场多步ＦＴＩＲ光谱技术结合ＣＯ吸附分子探针方法，研究了Ｒｈ电极表面分子过程。在电化学处理后的光滑Ｒｈ电极表面上首次检测到两种ＣＯ孪生吸附态及其随电位变化过程。使用电位循环扫描方法改变Ｒｈ电极表面状态，在０．０５ｍｏｌ／ＬＨ２ＳＯ４酸性溶液中，选取－０．２７５至２．４Ｖ电位区间和１．５Ｖ／ｓ扫描速率对Ｒｈ电极进行循环扫描处理２ｍｉｎ，处理后的Ｒｈ电极表面积累一层氧化物，ＣＯ以孪生态吸附于表面Ｒｈ氧化物上，在２１６６和２１１２ｃｍ－１处给出一对宽的ＩＲ吸收峰；在负电位下，表面氧化物被还原生成表面Ｒｈ原子簇，ＣＯ仍以孪生态吸附于表面Ｒｈ原子簇上，在２１０２和２０３２ｃｍ－１处给出一对尖的ＩＲ吸收峰；表面Ｒｈ原子簇不稳定，随着电位正移分解和扩散形成平滑的Ｒｈ表面，此时ＣＯ则以线式和桥式吸附于平滑的Ｒｈ表面，分别在２０４８和１９１９ｃｍ－１处给出两个ＩＲ吸收峰。

Because of its great importance both in electrocatalysis and C1 chemistry applications, the adsorption of CO on metallic electrodes such as Pt, Pd, Au, Ag, RhF￣[1～2], etc. has been extensively studied by in situ infrared spectroscopy Since 1981. In all these studies only three types of CO adsorbates, i. e. , linear (2 090～2 000 cm￣(-1)), bridgrd (2 000～1 900 cm￣(-1)) or multi-bonded (1900～1 800 cm￣(-1)) species, were identified. A different absorbate, twin CO on rhodium ((Rh (CO)2) , does exist on the solid/gas interface of highly dispersed Rh or Rhn clusters[3～4] on supports,this species originating a doublet at 2100 and 2030 cm￣(-1) for its symmetrical and asymmetrical stretch modes, respectively. To our knowledge, this doublet has not been reported yet for the Rh/electrolyre interface.