Resolving the HUPD and HOPD by DEMS to determine the ECSA of Pt electrodes in PEM fuel cells

Overpotential deposited hydrogen (H-OPD) and underpotential deposited hydrogen (H-UPD) are produced together on Pt in acidic media between 0 and 110 mV vs. SHE and cannot be resolved by cyclic voltammetry alone. Differential electrochemical mass spectrometry was demonstrated for the first time to resolve H-OPD and H-UPD by measuring the H-2 evolved from water by the hydrogen evolution reaction at the cathode (a Pt electrode) of a proton exchange membrane fuel cell (PEMFC). The H-UPD at the cathode was thus quantified and determined to form a saturated layer on the Pt surface when the lower potential limit of cyclic voltammetry is below about 70 mV vs. the anode, a dynamic hydrogen electrode. This amount of H-UPD can be used to measure the ECSA of a Pt electrode in PEMFC and avoid the error from including H-OPD. (C) 2011 Published by Elsevier B.V.