Durability of single-walled (SWCNT) and multiwalled carbon nanotubes (MWCNT) as Pt supports was studied using two accelerated durability tests (ADTs), potential cycling and potentiostatic treatment. ADT of gas diffusion electrodes (GDEs) was once studied during the potential cycling. Pt surface area loss with increasing the potential cycling numbers for GDE using SWCNT was shown to be higher than that for GDE using MWCNT. In addition, equilibrium concentrations of dissolved Pt species from GDEs in 1.0？M H2SO4 were found to be increased with increasing the potential cycling numbers. Both findings suggest that Pt detachment from support surface plays an important role in Pt surface loss in proton exchange membrane fuel cell electrodes. ADT of GDEs was also studied following the potentiostatic treatments up to 24？h under the following conditions: argon purged, 1.0？M H2SO4, 60°C, and a constant potential of 0.9？V. The subsequent electrochemical characterization suggests that GDE that uses MWCNT/Pt is electrochemically more stable than other GDE using SWCNT/Pt. As a result of high corrosion resistance, GDE that uses MWCNT/Pt shows lower loss of Pt surface area and oxygen reduction reaction activity when used as fuel cell catalyst. The results also showed that potential cycling accelerates the rate of surface area loss. 1. Introduction The durability of proton exchange membrane fuel cell (PEMFC) is a major barrier to the commercialization of these systems for stationary and transportation power applications. Gas diffusion electrodes (GDEs) of PEMFCs use electrocatalysts for the oxidation of hydrogen at the anode and reduction of oxygen in air at the cathode. Currently, Pt supported on high surface area carbons is the best feasible electrocatalyst for PEMFC systems [1]. Limiting the commercialization of PEMFCs, electrocatalyst durability is a factor for consideration [2–4]. The degradation mechanisms proposed include catalyst dissolution [5, 6] and carbon support corrosion [7]. Carbon supports corrosion in acidic electrolytes involves the general steps of oxidation of carbon in the lattice structure (Reaction (1)) followed by hydrolysis (Reaction (2)) and finally gasification of the oxidized carbon to (Reaction (3)), wherein the subscript ‘‘ ’’ denotes surface species [8, 9]: One strategy to decrease carbon support corrosion is to use carbon with high extent of graphitization, which is due to decreased defect sites on the carbon structure, where carbon oxidation starts [10, 11]. With the development of novel carbon nanostructure materials [12], for example,
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