Influence of the Working and Counter Electrode Surface Area Ratios on the Dissolution of Platinum under Electrochemical Conditions

Abstract

The potential variation of a Pt counter electrode (CE) in a three-electrode configuration is monitored as the potential of a Pt working electrode (EWE) follows a triangle-shaped program in 0.5 M aqueous H2SO4. The spontaneously adopted CE potential (ECE) is reported for different values of the ratio of geometric surface areas of WE and CE (Ageom,WE/Ageom,CE). The ECE versus time (t) transients are nonlinear and resemble charging/discharging curves. In the case of Ageom,WE > Ageom,CE, ECE adopts higher values than EWE and vice versa. In the case of Ageom,WE/Ageom,CE = 10/1, the values of ECE are 0.3–0.4 V higher than the highest values of EWE. The high ECE values give rise to the development of a thick surface oxide that undergoes subsequent dissolution. A novel three-compartment electrochemical cell is employed to examine simultaneously the dissolution of WE and CE and to monitor their potentials; the amount of dissolved Pt is quantitatively analyzed using inductively coupled plasma mass spectrometry. The...