• Andersen, Shuang Ma

Abstract

Accelerated stress test (AST) protocol meant to study the durability of catalyst support (carbon) for the state-of-the-art electrocatalyst used in the polymer electrolyte membrane fuel cells (PEMFCs), i.e., Pt nanoparticles supported on high surface area carbon (Pt/C) has been evaluated critically. For the Pt/C electrocatalysts, the AST meant to study the support durability consists of potentiodynamic treatment, e.g., potential cycling for the potentials > 1.0 V, where the Pt surface is passivated through surface oxides and the corrosion of support carbon is prominent degradation mechanism. We have observed that potential cycling between 1.0 and 1.6 V (vs. RHE) in sulfuric acid or perchloric acid electrolyte causes significant impact on the catalyst particles presumed to be passivated due to formation of oxide layer. X-ray diffraction (XRD) patterns of pre-AST and post-AST samples (Figure 1) suggest significant change in crystallite size during potential cycling between 1.0 and 1.6 V (vs. RHE), which may be considered to growth induced by dissolution/redeposition rather than particle growth through agglomeration due to support corrosion. Based on quantification of the degradation mechanisms,1, 2, significant (~50%) electrochemical surface area loss due to catalyst particle growth during support corrosion AST should be taken into account while development/screening of durable catalyst supports.

Topics

• nanoparticle
• impedance spectroscopy
• surface
• polymer
• Carbon
• corrosion
• x-ray diffraction
• durability