Hydrogen diffusion effects on the kinetics of the hydrogen electrode reaction. Part I. Theoretical aspects

GENNERO DE CHIALVO, MARÍA ROSA; CHIALVO, ABEL CÉSAR

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

Royal Society of Chemistry

Lugar: Londres; Año: 2004 vol. 6 p. 4009 - 4017

1463-9076

The effect of the hydrogen diffusion on the hydrogen electrode reaction has been studied and rigorous kinetic expressions for the Tafel-Heyrovsky-Volmer mechanism has been derived. The analysis of the dependences of the current density (j) on overpotential (h), particularly oriented to the hydrogen oxidation reaction (hor), leads to the following main results: (i) In the Tafel-Volmer (TV) route, the current density reaches a maximum value ( jmax) less or equal to the limiting diffusion current density ( jL); (ii) jmax is always equal to jL for the Heyrovsky-Volmer (HV) route; (iii) In the simultaneous occurrence of both routes (THV), the current density always reaches the jL value, although in the range of overpotentials of applied interest (0 £ h / V £ 0.6) the jmax value characteristic of the TV route can be also obtained.             The Levich-Koutecky plots have been also analysed and it has been demonstrated that the dependence j(h) for the hor under activated control cannot always be obtained from these plots.