Effect of the crystallographic orientation of Ag single crystal face electrodes on the kinetics of proton discharge

Proton reduction from acidic solutions has been investigated on Ag single c rystal faces by means of capacitance curves, slow potentiodynamic measureme nts, and impedance. Both low-index and high-index faces have been studied. The reaction has been found to proceed with a Tafel slope close to 120 mV a nd a reaction order of 1. The overpotential is higher for Ag than for Au, w hile the crystal face sequence is just the opposite. The data have been dis cussed in terms of ion adsorption, as well as competition between water and hydrogen intermediate adsorption. (C) 1999 Elsevier Science S.A. All right s reserved.