ELECTROCHEMICAL QUARTZ-CRYSTAL MICROBALANCE MEASUREMENTS OF CO ADSORPTION AND OXIDATION ON PT IN VARIOUS ELECTROLYTES

The adsorption behaviour of Pt was investigated with the electrochemic al quartz microbalance during potential scanning in acid electrolytes. From the mass increase with potential it is concluded that in the pot ential range of hydrogen desorption and double layer both water and an ions are adsorbed in H2SO4 and H3PO4, whereas in HClO4 there is only a dsorption of water molecules. The mass changes in the oxygen region in dicate that anions are included in the oxide layer. The Pt/COads syste m was studied in H2SO4, HClO4 and H3PO4. The presence of adsorbed CO i s observed as a mass increase with respect to the CO-free system. The results show that water is adsorbed on top of the adsorbed CO layer at low potentials. Moreover, it can be concluded from the mass-balance d ata that water molecules are attached to the hydrogen monolayer at 0.0 3 V vs R.H.E. in sulfuric and perchloric acid, but not in phosphoric a cid. (C) 1997 Elsevier Science Ltd.