Corrosion Behavior of Platinum in Aqueous H2SO4 Solution: Part 1—Influence of the Potential Scan Rate and the Dissolved Gas

Abstract

Research on the degradation of Pt materials is of high importance to the polymer electrolyte membrane fuel cells (PEMFCs) technology, since their degradation translates into irreversible materials loss and significant deterioration of the PEMFCs’ performance. Polycrystalline platinum (Pt(poly)) serves as a model system in research on Pt-based electrocatalysts for PEMFCs due to its randomly oriented grains separated by grain boundaries, and experimental studies using Pt(poly) create important background knowledge that may be used to identify and understand electrochemical and corrosion phenomena taking place in PEMFCs. In this contribution, we report new results on the corrosion behavior of Pt(poly) in 0.50 M aqueous H2SO4 solution saturated with a neutral (N2(g)) or reactive gas (O2(g) or H2(g)). We analyze the influence of the potential scan rate (s = 0.10, 0.20, 0.50, and 1.00 mV s−1) on the polarization behavior of Pt(poly) in anodic (positive-going) and cathodic (negative-going) directions. A comparative analysis of the impact of dissolved gases on the electrochemical and corrosion behavior of Pt(poly) is performed using cyclic voltammetry and potentiodynamic polarization. Their analysis reveals that the corrosion data obtained at the lowest potential scan rate (s = 0.10 mV s−1) are the most accurate and representative of the corrosion of Pt(poly) in 0.50 M aqueous H2SO4 solution. This is due to the fact that polarization measurements are designed to mimic steady-state conditions, which can only be achieved in the case of s = 0.10 mV s−1 or lower. A comparison of the corrosion data leads to the following observations: (i) Pt(poly) does not undergo corrosion in the electrolyte saturated with H2(g), (ii) it undergoes a slight corrosion in the electrolyte outgassed with N2(g), (iii) it undergoes a substantial corrosion in the electrolyte saturated with O2(g), and (iv) the corrosion rate is more significant in the case of the anodic transient than the cathodic ones (for the same dissolved gas).