Ab. Anderson et E. Grantscharova, CATALYTIC EFFECT OF RUTHENIUM IN RUTHENIUM-PLATINUM ALLOYS ON THE ELECTROOXIDATION OF METHANOL - MOLECULAR-ORBITAL THEORY, Journal of physical chemistry, 99(22), 1995, pp. 9149-9154
An atom superposition and electron delocalization molecular orbital (A
SED-MO) study has been made of the catalytic effect of Ru alloyed into
Pt electrodes on the oxidation of the adsorbed CO poison that is gene
rated during methanol fuel cell operation. Using cluster models of the
Pt(lll) surface, the Ru in Pt(111) alloy surface, and the Ru(0001) su
rface, it is found that the H2O adsorption energy to surface atoms inc
reases in the order Pt in Pt(lll) < Ru in Pt(lll) < Ru in Ru(0001). An
inverse relationship is found for OH activation energies: the stronge
r the adsorption, the more easily the reaction H2O(ads) --> OH(ads) H(ads) takes place. The values and potential dependencies of these act
ivation energies are consistent with OH(ads) being the oxidizing speci
es that removes the CO(ads) poison. Both the Pt and the alloy surfaces
are calculated to have increasing activation energies with increasing
potential for the CO(ads) oxidation step. In both cases high coverage
of coadsorbed CO, OH, or other species will. activate CO(ads) and OH(
ads) by weakening their chemisorption bond strengths.