Electrochemical corrosion studies of carbon supports and electrocatalysts and their effects on the durability of low-temperature PEM fuel cells

Performance of a PEM fuel cell relies heavily on the durability of the platinum and platinum-alloy based electrocatalysts supported on carbon blacks. Carbon corrosion has been widely accepted as an important issue affecting the degradation of the catalytic layer in PEMFCs. Traditional carbon blacks used in today's fuel cell industry are not tailored to suit the corrosive conditions encountered in PEMFCs.;Advanced carbon supports should have excellent electrochemical corrosion resistance, good conductivity, high surface area and optimum hydrophilic properties. The principal objective of this work is to investigate the corrosive behavior of carbon blacks and electrocatalysts supported on such carbon blacks in conditions that are typical for fuel cells. Physical and chemical changes during oxidation of these carbon blacks have been reviewed along with methodology for studying their corrosion in a low-temperature fuel cell environment. This study provides an ex-situ corrosion measurement protocol and a gas diffusion electrode half-cell setup to study the electrochemical oxidation resistance behavior of standard carbon blacks, modified carbon blacks, and advanced carbon supports in acid electrolyte at 25°C. Corrosion current-time relationships were evaluated and transient mode of corrosion study was employed to simulate automobile startup/shutdown. The effects of various surface modifications on carbon corrosion behavior have been studied in detail. The aggravated corrosion of carbon supports at potentials higher than the thermodynamic stable regime of water was investigated and a mechanism is proposed to address the same. The role of the metal phase on carbon corrosion at the catalyst-support interphase has also been investigated. The corrosion current dependence on the microstructure and nature of surface groups present on these carbons was examined.;Further, measuring carbon corrosion effects on the durability of a single membrane-electrode assembly (MEA) cathode with catalyst, air/nitrogen and NafionRTM system (in-situ) using an adapted durability protocol is a key contribution from this research. Multivariate analysis (MVA) has been used to correlate electrochemical behavior to physical, morphological and structural properties. Principal Component Analysis (PCA) was used to visualize the correlation between all relevant structural (XPS), microscopic (SEM), physical parameters and corrosion kinetics. Models have been proposed to predict corrosion behavior from structural and physical parameters.