Adsorption and Electinoxidation of Carbon Monoxide on High-Index Pt Single Crystals as Model Electrochemical Catalysts

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In order to simulate the electrochemical reactions taking place on fuel cell catalysts, Pt(111), Pt(10 10 9), and Pt(20 19 19) surfaces were prepared, and the electroocidation reaction of carbon monoxide in perchloric acid solution was investigated by electrochemical measurements and scanning turnneling microscopy (STM). Stakes of single crystal electrodes ware prepared by annealing in a hydrogen flame and quenched in a pure water.On both Pt(111) and stepped surfaces, electrooxidation of carbon monoxide started at ca. 0.4 vs RHE, but the onset electrode potential shifted in the anodic direction as the potential was warmed between 0.05 and 12 V After the 30 cycles, the onset potential for the electrooxidation of carbon monoxide became ca. 0.7 V on all the surfaces By STM, it was revealed that the steps were initially smooth and round, but as the potential scan continues, the steps became mom straight-like Small atomic-high islands of Pt was also bind by STM. It was suggested that after the cycling, atomic defects, such as kinks and adatoms, were diffused on the surface and trapped by other defects to make less-defected Pt surface.When the surface was treated with IR heating method, steps were more orderly arranged, but the electrooxidation activity was not lowered, showing the existence of atomic defects on the surface.The investigation open up the new insight into the electrooxidation of carbon monoxide.