Chemical modification of fuel cell catalysts and electrochemistry of proton exchange membrane fuel cell electrodes

One of the major goals of this research was to investigate ion transport within the catalyst layer of fuel cell electrodes and attempt to improve it. -- One method used to study ion transport within fuel cell electrodes was to incorporate electroactive metal complexes into the catalyst layer to act as a probe. It was found that a lower fraction of the complexes were electrochemically active in the cathode of an operating fuel cell, compared to similar electrodes in contact with an aqueous sulfuric acid solution. It is anticipated that in many cases, the method of electroactive probes will be more advantageous than (or complimentary to) standard methods. -- Electrochemical impedance spectroscopy was also used to study ion transport in fuel cell catalyst layers. It was found that limiting capacitance correlates with active area. Also, results indicate that the non-ideal impedance behavior of fuel cell electrodes is due to variation of their ionic conductivity with distance from the membrane. -- In order to increase proton conductivity in the catalyst layer, we have explored the attachment of a sulfonated silane directly to the catalyst surface. It was found that the modified catalysts outperformed the unmodified catalyst at low Nafion loadings (