Nanoscale current imaging of the conducting channels in proton exchange membrane fuel cells

FUEL 19

James R. O'Dea, jodea@chem.ucsb.edu1, David A. Bussian, dabus@lanl.gov2, Horia Metiu, metiu@chem.ucsb.edu1, and Steven K. Buratto, buratto@chem.ucsb.edu1. (1) Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106-9510, (2) Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545
The electrochemically active area of a proton exchange membrane in an operating fuel cell is investigated using conductive probe atomic force microscopy. A platinum coated AFM tip functions as a nanoscale cathode as it scans the surface of a membrane, the opposite side of which has been hot pressed to a gas diffusion electrode and is continuously exposed to hydrogen gas while imaging. This configuration allows investigation of proton conducting channels within the membrane, including their number, connectivity, and conductivity. Correlations and anti-correlations between hydrophilic surface domains and ion conductive channels are made by overlaying tapping mode and conductive AFM images taken on the same region of a given sample. Studies done on Nafion membranes indicate that a large number (~60%) of the aqueous domains present at the membrane's surface are electrochemically inactive, which may be due to a combination of limited aqueous domain connectivity and catalyst accessibility.
 

Fuel Cell Technology: Polymer Electrolyte Membrane Fuel Cell Systems
8:25 AM-12:00 PM, Sunday, August 19, 2007 Boston Park Plaza -- Cambridge Rm, Oral

Division of Fuel Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007