STRUCTURAL SENSITIVITY IN THE ELECTROCATALYTIC PROPERTIES OF Pt - 1. HYDROGEN ADSORPTION ON LOW INDEX SINGLE CRYSTALS AND THE ROLE OF STEPS.

Single crystal surfaces were used to examine the structure sensitivity of hydrogen chemisorption on Pt in dilute acid electrolyte. An electrochemical cell was coupled directly with an ultrahigh vacuum system, and low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) were used to determine the structure and composition of the electrode surfaces. Hydrogen adsorption was examined by triangular sweep cyclic voltammetry. Contributions to the multiple peaks observed in voltammograms of Pt due specifically to anions were deduced and the effects of surface geometry alone were determined. A difference in hydrogen bond energy (3. 4 kcal/mole) was observed for hydrogen on the (111)-(1 multiplied by 1) and the (100)-(1 multiplied by 1) surface.