Influence of rare-earth metals on adsorption and oxidation of carbon monoxide on rhodium

The presence of gadolinium, cerium, and lanthanum in rhodium catalysts vapor-deposited as films or prepared on silica supports enhances rhodium catalytic activity toward oxidation of CO at 370-670 K. The IR and X-ray photoelectron spectra of chemisorbed CO and the conductometric titration and thermodesorption data show that the promoting action of rare-earth metals is explained by an increase in the total amount of adsorbed CO, a decrease in the fraction of geminal and linear adsorbate forms and predominance of the bridge form at the temperature of catalysis, the formation of carbonate and carboxylate structures, change of the sign of polarization of adsorbed CO molecules, a decrease in the strength of bonds between CO and the catalyst, and a change in the oxidation state of rhodium caused by interaction with oxide forms of rare-earth metals.