IN-SITU FTIRS STUDY OF THE ELECTROCATALYTIC OXIDATION OF CARBON-MONOXIDE AND METHANOL AT PLATINUM-RUTHENIUM BULK ALLOY ELECTRODES

The electro-oxidation of carbon monoxide and methanol on platinum-ruth enium bulk alloys was investigated by cyclic voltammetry and in situ F TIR reflectance spectroscopy. Electrochemical measurements revealed th at these two oxidation reactions are dependent on the ruthenium compos ition in the alloy. For CO oxidation, the alloy with an Ru concentrati on of 50 at.% allows this reaction to occur at lower potentials than o n pure platinum or pure ruthenium. Conversely, methanol electro-oxidat ion gives higher current densities on alloys, containing 10-15 at.% Ru . With FTIRS measurements, it was found that, during methanol oxidatio n on Pt-Ru alloys, CO, but also small amounts of HCHO and HCOOH, are f ormed, the surface distribution of which depend on the alloy compositi on. The COads absorption bands are quite absent in spectra correspondi ng to alloys with the optimum composition (15-20 at.% Ru). On the othe r hand, during the oxidation of gaseous CO on alloys with the optimum composition (Pt0.5Ru0.5), the CO2 formed is not adsorbed on the electr ode surface, the opposite of the other compositions. These results sug gest strongly that the rate determining step for both reactions is the formation of adsorbed OH on the ruthenium surface. (C) 1998 Elsevier Science S.A. All rights reserved.