Study of the Hydrogen Electrode Reaction on Ruthenium Electrodes: Evaluation of the polarization resistence as a function of the proton activity

MARIA SOL RAU; PAOLA QUAINO; M. R. GENNERO DE CHIALVO; A. C. CHIALVO

Sevilla

Congreso; The 59th Annual Meeting of the International Society of Electrochemistry-ISE; 2008

The International Society of Electrochemistry - ISE

The kinetic parameters of the hydrogen electrode reaction (HER) can be evaluatedthrough the dependence of the equilibrium polarization resistence (Rp) with the proton activity (aH+) and/or the hydrogen partial pressure (PH2) under well-definedhydrodynamic conditions. In this context, the present work proposes a methodology for the evaluation of the kinetic parameters of the hydrogen electrode reaction for the Tafel-Heyrovsky-Volmer mechanism from experimental results corresponding to the evaluation of the current density dependences jexp(η,aH+,ω) around the equilibrium potential on a rotating disc ruthenium electrode. The experimental determinations were carried out in the overpotential range (-0.010 ≤ η / V ≤ 0.010) by the application of a program of overpotential pulses at different rotation rates (900 ≤ ω/ rpm ≤ 8100) and pH values (0.1 ≤ pH ≤ 2.0). The electrolyte solution was H2SO4 prepared with triply distilled water. Measurements were carried out at 30 ºC under hydrogen gas (99.999 % purity) bubbling at 1 atm, ensuring a continuous saturation of the electrolyte with molecular hydrogen. The equilibrium polarization resistence Rp(aH+) was obtained according to (1):lim (ω --infin)Rp(exp) (aH+,ω )= Rp (aH+)where the experimental polarization resistence (Rp(exp)=∂η/∂j|η=0) takes into account the diffusional and activated contributions and Rp(aH+) represents the condition in the absence of mass transport. Finally, the kinect parameters were obtained by the correlation of the dependence Rp(aH+) with theoretical expressions.