Accelerated entry of hydrogen into iron from NaOH solutions at low cathodic and low anodic polarisations

• DOI: 10.1016/j.electacta.2006.09.030
• Publication Date: 2006-10-15T06:45:08Z
• Authors: I. Flis-Kabulska; T. Zakroczymski; J. Flis
• Keywords: 02 engineering and technology; 0210 nano-technology

Abstract Hydrogen entry into iron from NaOH solutions and from 0.05 M H 2 SO 4 during voltammetric cycling was studied with the electrochemical permeation technique. Measurements were carried out on 35-μm thick membranes at 25 °C. Accelerated entry of hydrogen was revealed by peaks of hydrogen permeation rate (HPR) which occurred at low cathodic and low anodic polarisations in NaOH solutions, but not in 0.05 M H 2 SO 4 . In cathodic scans the HPR peak occurred at potentials of an oxide reduction, probably of Fe 3 O 4 to Fe(II), whereas in anodic scans this peak appeared at potentials of the oxidation of iron to Fe(II) and to Fe 3 O 4 , and it was distinct especially at high scan rates. X-ray photoelectron spectroscopy (XPS) surface analysis indicated that the fraction of Fe 3 O 4 in the surface film during cathodic scans was at the potential of HPR peak significantly larger than that at a nobler potential. It is suggested that the occurrence of HPR peaks can be due to a partial removal of surface layers and to the formation of species promoting the hydrogen entry, supposedly Fe 3 O 4 without or with Fe(II). Possibly, these species might be effective by hindering the recombination of H ads or by blocking adsorption sites.