PtおよびPd表面上のCO酸化反応で生成した振動励起CO2分子の赤外発光測定
1991 年 12 巻 10 号 p. 635-640
詳細
1991 年 12 巻 10 号 p. 635-640
Vibrational energy distributions in CO2 molecules formed by the catalytic oxidation of CO on Pt and Pd surfaces have been measured by using infrared emission spectroscopy. The reactants (the total flux of CO and O2: 1.3×1019 molecules/cm2·s) were supplied to the surface through two free jet nozzle sources, while an FT-IR spectrometer was used to obtain the infrared emission spectra (4 cm-1 resolution) of the product CO2. For all the experimental conditions (surface temperature in the range of 650∼1150K and O2/CO ratio from 5/1 to 1/5), the emission spectra observed in the 2400∼2100 cm-1 region were significantly red shifted from the fundamental of the asymmetric streth at 2349 cm-1, indicating that the CO2 molecules were vibrationally excited substantially beyond thermal equilibrium with the surface. The surface coverage of oxygen on both Pt and Pd was varied by changing the O2/CO ratio and, in both cases, increasing oxygen coverage caused an increase in the average vibrational temperature. This is in stark contrast with that by Brown and Bernasek who reported that the average apparent CO2 vibrational temperature decreased with increasing surface oxygen coverage. The average vibrational temperature was much higher on Pd than on Pt. This is in good agreement with that by Coulston and Haller who suggested that the activated complex is bent more on Pd than on Pt.
