POTENTIAL DEPENDENCE OF CO OXIDATION BY H2O ON A PT ANODE - A MOLECULAR-ORBITAL THEORY

The electrochemical oxidation of CO on Pt anodes by water has been studied with the atom superposition and electron delocalization molecular orbital (ASED-MO) theory. By using a Pt cluster to represent the Pt(111) surface and then shifting the Pt valence band down in energy to represent the result of applying a positive potential to the electrode, a potential step for the overall anodic process H2O+CO --> CO2+2H++2e- has been found. This corresponds to the debonding of an H2O..CO intermediate from the electrode surface with the simultaneous loss of 2H+ to the solution and 2e- to the anode, releasing CO2. Formation of this intermediate itself is calculated to have an activation barrier with insignificant potential dependence.