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Pulsatile Fuel Cell Operation, 03-9049

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Principal Investigators
Craig M. Wall
Michael A. Miller

Inclusive Dates: 10/01/97 - Current

Background - Research originally intended to explore methods of enhancing proton exchange membrane fuel cell operation by exploiting transient surges during unsteady operation had a serendipitous outcome: it was discovered that adding an interposed metallic layer within the membrane itself conferred a pseudo-capacitive functionality on the cell. This capability allowed the cell to be charged with an input of electrical energy that could then be discharged at rates well above steady-state levels.

Approach - SwRI engineers, drawing on research into fundamental processes, attempted to understand the oscillating behavior sometimes seen in fuel cells undergoing progressive failure. After gaining some critical knowledge, engineers developed a new cell architecture that included a third electrode intended to be used as a gate, so that the cell operation could be controlled in a manner similar to transistors or vacuum tubes. Including a conducting metallic layer embedded within the membrane resulted in several novel and potentially beneficial properties.

Accomplishments - The most striking effect demonstrated to date has been the ability to operate the cell in a pulsatile mode, in which the discharge rate can be briefly raised to several times that normally discharged by the cell. This capability has important implications for vehicular applications. In addition, the interposed electrode enables direct electrical sensing of the membrane hydration, an increasingly useful ability as cells are pushed to higher current densities. Finally, direct control of the catalytic conditions on the anode and cathode by the use of the gate electrode has been demonstrated. Indeed, the third electrode architecture has made possible more accurate measurements and the construction of theoretical models not previously possible. 

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