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利用红外光谱方法考察了在Pt/Al_2O_3催化剂上Pt晶粒大小和共吸附H_2O对CO吸附态的影响。共吸附H_2O可使CO在Pt/Al_2O_3上的线式吸收带产生远大于文献报道过的红移(△vco=40厘米~(-1) ),谱带宽化和强度增加,而在Pt/SiO_2催化剂上则没有发现类似的效应。还发现CO的吸收带位置因Pt粒子大小不同而异,当D_(pt)足够大时,在共吸附H_2O的作用下,CO在Pt/Al_2O_3上的线式吸收带分裂成双峰,其中高波数峰对H_2O的作用不敏感,低波数峰对H_2O的作用敏感。提出了Al_2O_3表面羟基可以和CO吸附态之间形成氢键的观点,可用以解释在Al_2O_3上高分散的Pt上和纯Pt金属表面上CO吸附态的不同特征。
The effect of Pt particle size and co-adsorption of H 2 O on the adsorption states of CO on Pt / Al 2 O 3 catalyst was investigated by infrared spectroscopy. The co-adsorption of H 2 O on the Pt / Al 2 O 3 linear absorption band is much larger than that reported in the literature (△ vco = 40 cm -1), broadening the band width and increasing the intensity. However, No similar effect was found on the catalyst. It is also found that the absorption band of CO varies with Pt particle size. When D pt is large enough, the linear absorption band of CO on Pt / Al 2 O 3 breaks into double peaks under the co-adsorption of H 2 O, The number of peaks is not sensitive to the effect of H_2O and the low wave number peak is sensitive to the effect of H_2O. The viewpoint that the hydroxyl groups on the surface of Al 2 O 3 can form hydrogen bonds with the adsorbed CO states can be used to explain the different adsorption states of CO on the highly dispersed Pt on Al 2 O 3 and pure Pt.