ADSORPTION OF HYDROGEN ON PLATINUM SINGLE-CRYSTAL ELECTRODES IN ACID AND ALKALI SOLUTIONS

The electrochemical behaviour of hydrogen and oxygen adsorption on platinum low- and high-index planes was examined in acid and alkali solutions. The features varied systematically with the surface structure and the pH of solution and are discussed in terms of steps and terraces of the respective surfaces. With respect to adsorbed hydrogen, Pt(111) provides mainly a long-range ordered adsorption site, Pt(100) both long-range and short-range ordered sites and Pt(110) mainly a short-range ordered site, respectively. The hydrogen wave observed on Pt(111) from 0.05 to 0.35 V has a very flat shape, like a platform, and is common in H2SO4, HClO4 and NaOH solutions. A monoatomic (111) step was confirmed to provide (110) sub-step sites along the step. With respect to adsorbed oxygen species, two peaks, PO,1 and PO,2, are observed at Pt(111) only in alkali solution. They are attributed to the adsorption of OH from water and O from OH, respectively. Interestingly, these species do not affect the surface structure, leaving the original surface when they are removed. © 1990.