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Kinetic Studies and Electrochemical Processes at Fuel Cell Electrodes

Stuckey, Philip A.
http://rave.ohiolink.edu/etdc/view?acc_num=case1322675454

Abstract Details

2011, Doctor of Philosophy, Case Western Reserve University, Chemical Engineering.
Kinetic parameters that describe the operating efficiency and rate of a reaction are revealed in situ by applying normal pulse voltammetry to normally operating proton exchange membrane fuel cells. The Tafel slope for the oxygen reduction reaction is directly extracted from the steady state chronoamperometric response. Conditioning potential, temperature, and relative humidity are varied independently to observe their effect on the Tafel slope. Aqueous ex situ techniques commonly used to collect kinetic data only mimic the conditions within fuel cell and are unable to capture true operating processes, especially the effects of relative humidity. The observed Tafel slopes are 47-62 mV/decade for oxide covered platinum indicating a smaller activation overpotential than that for oxide free platinum with Tafel slopes of 91-119 mV/decade in initial studies. High temperature operation at 120°C showed no kinetic or mechanistic benefit compared to fuel cell operation at 80°C. If high efficiency is desired, the fuel cell should be operated in a potential range where oxide is present on the platinum surface. A novel technique is presented using pulse voltammetry measure platinum oxide coverage in situ on PEMFC electrodes. A linear logarithmic rate was noticed for oxide conditioning times longer than 1 second. Extended testing of relative humidity effects at 80 °C, combined with electrochemical active surface area measurements to normalize the oxide growth, showed a growth rate of 28 μC cm-2 (log s)-1 and also provided the ability to monitor platinum dissolution from the electrode. Concepts from both these projects are assimilated to develop novel pulse voltammetry waveforms that are applied in situ on normally operating proton exchange membrane fuel cells to reveal Tafel kinetics with control of adsorbed oxide on platinum. The results show that the Tafel slope decreases with increasing platinum oxide coverage on the electrode. The oxidation of higher order polyols such as glycerol would have profound impacts in the fuel cell arena considering the abundance of glycerol and its low price in the marketplace. Glycerol would provide a fuel with higher energy density than hydrogen. Preliminary results from glycerol oxidation studies on Pt, Pt-Ru, and Pt-Cr are reported.
Thomas Zawodzinski, Jr. (Advisor)
Jay Mann, Jr. (Committee Chair)
Mohan Sankaran (Committee Member)
David Schiraldi (Committee Member)
Alternative Energy; Analytical Chemistry; Chemical Engineering; Energy; Engineering; Mechanical Engineering
Fuel cell; electrochemistry; pulse voltammetry; Tafel slope; oxygen reduction reaction; platinum; oxide; in situ; kinetics; proton exchange membrane fuel cell; normal pulse voltammetry; chronocoulometry; chronoamperometry; glycerol; hydrogen

Recommended Citations

Citations

  • Stuckey, P. A. (2011). Kinetic Studies and Electrochemical Processes at Fuel Cell Electrodes [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1322675454

    APA Style (7th edition)

  • Stuckey, Philip. Kinetic Studies and Electrochemical Processes at Fuel Cell Electrodes. 2011. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1322675454.

    MLA Style (8th edition)

  • Stuckey, Philip. "Kinetic Studies and Electrochemical Processes at Fuel Cell Electrodes." Doctoral dissertation, Case Western Reserve University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1322675454

    Chicago Manual of Style (17th edition)

case1322675454
3,180
© 2011, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.
Release 3.2.12