The investigation of the kinetics and mechanism of hydrogen evolution reaction on tin

The mechanism and kinetics of the hydrogen evolution reaction (HER) on tin electrode in 0.1 M H2SO4 solution were studied using the methods of steady-state polarization and electrochemical impedance spectroscopy. The simulation of the data obtained from these two methods, using nonlinear fitting procedure allowed us to determine the rate constants of Volmer, Heyrovsky and Tafel steps associated with the mentioned reaction. The kinetic results indicate that HER mechanism at low negative potentials is a serial combination of Volmer step and parallel Tafel and Heyrovsky steps. At high negative potentials where the hydrogen coverage reaches its limiting value, a Tafel line with the slope of - 126 mV dec(-1) is obtained. In this potential region the mechanism of the HER follows Volmer-Heyrovsky while the Tafel step has negligible contribution. The kinetic studies indicate that the rate of HER is controlled by the Volmer step. (C) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.