Hydrogen adsorption on single-crystal platinum electrodes in alkaline solutions

Abstract Hydrogen adsorption on single-crystal platinum low-index and stepped surfaces was studied in 0.1 M and 0.01 M NaOH solutions. A strong dependence on the crystallographic orientation of the electrode surface was found. The multiple states of hydrogen were correlated with the symmetry of surface sites. The data for the stepped surfaces were found to be useful in explaining the nature of processes occurring on the low index surfaces. Several strong indications were found for the nature of the so-called “butterfly” peak, indicating that it is due to adsorption of the hydroxil species rather than to hydrogen adsorption. Indications for hydrogen adsorption on Pt(111) in the H2 evolution region was found by impedance measurements. An effort was made to identify the multiple adsorption states for Pt(100). Hydrogen adsorption on the step sites for surfaces from all three crystallographic zones was identified and found to be proportional to the step density. A comparison with hydrogen adsorption in acid solutions was made for some surfaces.