TPD and IR spectroscopic studies of CO, CO 2 and H 2 adsorption on LaCrO 3

Abstract

The surface interaction of H 2, CO and CO 2 with oxidized and reduced LaCrO 3 were studied by means of temperature programmed desorption and infrared spectroscopies. CO single adsorption at 298 K gave rise to CO TPD peaks (375–765 K) assigned to linear and bridged species and to CO 2 peaks (425–810 K) assigned to bidentate carbonates (infrared bands at 1655, 1625, 1290 and 1055 cm −1). CO 2 single adsorption yielded CO 2 TPD peaks (365–730 K) assigned to bidentate carbonates (infrared bands at 1615, 1310 and 1045 cm −1). CO and CO 2 desorption spectra after CO adsorption and after H 2CO successive adsorption on LaCrO 3 reduced at 923 K showed that hydrogen preadsorption does not affect in any significant way the subsequent CO adsorption. However, the TPD spectrum of H 2 obtained after H 2 adsorption is substantially modified by CO preadsorption (COH 2 sequence) or by CO subsequent adsorption (H 2CO sequence). Significant differences were also found in CO and CO 2 TPD spectra after CO single adsorption and after COH 2 successive adsorption. These differences are interpreted to be due to a strong interaction between CO and hydrogen in the adsorbed state. These results are consistent with the formation of an oxygenated surface species after the COH 2 adsorption sequence.