Matthew J. Watt-Smith

Determination of the electrochemically active surface area of Pt/C PEM fuel cell electrodes using different adsorbates

The characterization of fuel cell electrodes is paramount to the optimum design and performance of fuel cell systems. The specific electrochemical surface area and structural properties of two Pt/C fuel cell electrodes have been determined. Three different electrochemical adsorbates, namely, H2 (adsorption and desorption), CO and Ag (underpotentially deposited, UPD) have shown that the estimated surface areas and roughness factors vary. These variations were shown to be ca 100% between Ag and H2 adsorption for the high-loaded sample, whilst for the low-loaded sample the difference is ca 30%. The surface areas obtained show that the low-loaded Pt electrode possesses a higher specific surface area than the higher-loaded sample. The results illustrate the importance of using multiple adsorbates to accurately determine and understand the structure of complex, porous fuel cell electrodes.

Simulation of mercury porosimetry using MRI images of porous media

Abstract Models of the pore structure of pellets taken from a batch of sol-gel silica spheres have been constructed from magnetic resonance images of the macroscopic (∼0.04-1 mm), spatial distribution of spin density and spin-spin relaxation time within the material. Simulations of mercury porosimetry on these models gave rise to good predictions for the point of deviation of the intrusion and retraction curves, and the level of mercury entrapment, in agreement with those found by experiment. This finding suggested that mercury intrusion and retraction within the pellets are determined by the macroscopic structure of the material, as detected using MRI.