Comparative Activity of (111), (100), (110), and Polycrystalline Platinum Electrodes in H2-Saturated 1M H[sub 2]SO[sub 4] under Potentiostatic Control

Abstract

Potentiostatic measurements of the three principle faces of oriented single Pt crystals and polycrystalline Pt showed some interesting comparisons. True areas are based on Pt atom densities, and under the electrochemical treatment used, no changes in these areas were found once the initial surface cleaning was completed. The hydrogen overvoltage was independent of crystal orientation or other metallurgical factors; however, the passivation of the hydrogen oxidation reaction and the oxygen generation reactions were different for each single crystal orientation with a large difference between these faces and a polycrystalline bead electrode. Steady‐state relations between potential and amounts of associated H atoms and number of sites available for coverage with O atoms were determined also. These steady‐state values are generally less than the comparative amounts found under transient conditions. Oxygen evolution on the Pt faces was not observed below a potential of 1.8V. It appears that grain boundaries, stress, and impurity inclusions may have more effect in determining the catalytic activity for some reactions than does the actual atomic density or geometry of Pt atoms.