Characterization of anodic fuel cell catalysts utilizing various surface sensitive techniques

The complete study of the interfacial properties of an electrocatalyst necessitates the use of multiple complementary surface sensitive techniques. The predominant tool to use in this study is electrochemistry. We used voltammetry and amperometry to study the deposition of nanoparticle catalysts onto inert working electrodes. We determined that spectroscopic grade graphite was a suitable substitute for commercially-obtained electrode supports, while Toray carbon paper was not suitable in the electrochemical testing environment. We also determined that the use of Nafion hindered the electrochemical response of nanoparticle electrodes for both hydrogen underpotential adsorption/desorption and fuel oxidation. There was a pronounced effect for formic acid oxidation on platinum/Nafion mixture, out of proportion to the surface area effects.; The spontaneously deposited Pt/Pd catalyst was optimized. The optimum palladium coverage for unsupported platinum black was theta = 0.79, whereas for carbon-supported platinum black it was theta = 1.39. The catalyst was also inspected via EC-IRAS, which indicated the presence of palladium on the surface and smaller particle sizes. It also revealed a potential tool for determining the poison from formic acid oxidation on palladium nanoparticles. Further, the efficacy of methyl formate oxidation on the catalyst was examined. This fuel was determined to hold no advantages over formic acid for oxidation with the Pt/Pd catalyst. This study also revealed the inadequacy of methanol oxidation on the Pt/Pd catalyst. Radiolabeling with electrochemistry was used to examine the poison/potential and poison/environment relationships. Poison from methanol and formic acid was determined to be strongly adsorbed CO, which was replaceable by CO passed through the electrolyte. The potentiometric differences between methanol and formic acid oxidation were also studied on a platinum black substrate. Formic acid oxidation was determined to go through the direct CO2 pathway, with poison buildup from CO formation only observed in a dynamic experiment in the HUPD region, indicating a reverse water-gas shift. Finally, we attempted to identify the poison species from formic acid oxidation on palladium. The experiments revealed that palladium is not significantly poisoned by carbon-containing species during formic acid oxidation.