The dynamics of CO oxidation on Pd, Rh, and Pt studied by high-resolution infrared chemiluminescence spectroscopy

Abstract

Hydrogen and CO spillover at Cu/Rh(100) bimetallic surfaces studied by highresolution electron energyloss spectroscopy J.Summary Abstract: Coadsorption structures of benzene and carbon monoxide on Rh(111) and Pt(111) by highresolution electron energy loss spectroscopy and lowenergy electron diffractionThe dynamics of carbon monoxide oxidation on Pd, Rh, and Pt foils were probed under nearly collision-free conditions using high resolution infrared chemiluminescence. Auger electron spectroscopy was used to verify the absence of impurities on the surfaces. The reactants were supplied to the surface through a free jet nozzle source, while a Fourier transform infrared spectrometer operating at 0.012 cm -I resolution was used to fully resolve the rotational structure of several vibrational transitions in the product CO 2 (22 in the case of Pd). In all cases, the product CO 2 is vibrationally excited and the apparent vibrational temperatures are in the same order as the peak reaction rates, i.e., Pd> Pt > Rh. The surface coverage of oxygen on Pd was varied by changing the CO:0 2 ratio and the surface temperature and, in both cases, increasing oxygen coverage causes an increase in vibrational excitation of product CO 2 , On Pt and Rh, the apparent temperatures of different vibrational modes are similar, while on Pd, those levels involved in Fermi resonances that are traditionally called the symmetric stretch levels are selectively populated. From these results, evidence that the activated complex is bent on Pd relative to Pt and Rh and, in all cases, is aligned more or less along the surface normal is presented.6932

Angular dependence of rotational and vibrational energies of product CO2 in CO oxidation on Pd(110)

“…After the CO 2 beam passed through two slits, the chemiluminescence from the CO 2 beam was detected in the same way as that for product states were expressed by rotational and vibrational temperatures. [13][14][15][16][17][18]23,[25][26][27] These expressions using temperatures may not be valid because previous works were conducted at high reactant pressures and population of rovibrational states of CO 2 after being scattered with reactants were studied. In order to obtain accurate populations of rovibrational states, state-resolved measurements should be conducted at low reactant pressures.…”

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] However, angle-resolved (AR) measurements [6][7][8][9][10][11][12] of internal energies have long been lacking in thermal surface reactions because of the difficulty in conducting such experiments, 18 although such measurements are required in order to obtain detailed structural information. In this paper, results of measurements of internal energies of AR product CO 2 in CO oxidation on Pd (110) are presented.…”

Surface species studied by angle-resolved product desorption: Emission mechanism and spatial distribution

“…In such a highly decreasing force field, the leaving molecule receives torque in a desorption event when it is inclined against the surface plane (Fig. 9d) [78]. The resultant desorbing molecule will have a small translational energy, yielding a broad angular distribution.…”

Internal-energy measurements of angle-resolved product CO2 in catalytic CO oxidation by means of infrared chemiluminescence

“…In each spectrum, a single broad peak appears in a range from 2400 to 2200 cm −1 , which consists of the contributions from a large number of transition lines corresponding to various initial rovibrational states. According to the previous measurements, [6][7][8][9][10][11][12] the populations of the vibrational and rotational states of product CO 2 are well expressed by the rotational and vibrational temperatures, T rot and T vib , in the frame of the Boltzmann distributions. For the present lowresolution spectra, the position of the broad peak shifts toward lower wave numbers as T vib increases.…”

“…Only the desorption process yielding products with hyperthermal energy can be examined as to the energy partitioning during the reaction event. [2][3][4] In fact, both the internal and translational energies of such hyperthermal products have been analyzed in some exothermic desorption processes, such as CO 2 in the CO oxidation 4,[6][7][8][9][10][11][12] and H 2 ͑or D 2 ͒ ͑Refs. [13][14][15][16][17] or N 2 ͑Refs.…”