Research and resources

Fuel cell and advanced battery materials laboratory

Principal investigator: Kenneth J. Wynne, Ph.D.

Phone: (804) 828-9303

Email: kjwynne@vcu.edu

Lab: Room 405

Acknowledgment: We are grateful for support of this research by NASA.

Proton exchange membrane fuel cells employ solid polymer electrolytes (typically Nafion) to provide ion (proton) transport from anode to cathode. A schematic and electrode reactions for hydrogen PEM fuel cells are shown in Figure 1.

Figure 1. Fuel cell schematic

The catalyst layer in PEM fuel cells usually consists of Nafion ionomer and carbon-supported Pt (or Pt alloy) catalyst. Previously, we developed a novel electrospraying technique to deposit catalyst layers on proton exchange membranes.¹ Fuel cells with e-sprayed catalyst layers exhibit state-of-the-art performance.

Recently, carbon “corrosion” during fuel cell operation was discovered. This oxidative degradation causes loss of fuel cell performance. To assess durability for carbon-supported Pt catalysts, we developed a TGA method. Figure 2 shows mass loss profiles for a number of carbon-supported Pt catalysts. This result clearly illustrates catalytic oxidation of carbon support by Pt. By assessing activation energies for different carbon substrates we plan to gain information important to understanding which substrates are most durable.

Figure 2. TGA curves for Vulcan XC 72 and 20, 40 and 46% Pt/Vulcan XC 72 in air.

References

1. O.A Baturina, G.E.Wnek, Characterization of Membrane-Electrode Assemblies Obtained by Electrostatic Processing. Electrochem. Solid-State Letters, 2005, 8(6), A267.

Material science for advanced Li batteries

Lithium solid polymer electrolyte batteries are rechargeable batteries that have technologically evolved from lithium ion/solvent batteries (Figure 1). Unlike solvent-based Li-Ion systems, lithium solid polymer electrolyte batteries contain a lithium salt electrolyte that is a soft hybrid polymer material. Advanced lithium-based chemistries coupled with polymer-based component concepts offer several important advantages. Unlike the organic solvent Li-Ion cells, SPE is not flammable. Thus these SPE-based batteries are less hazardous if mistreated. Another important advantage is the ability for making battery cells very thin, as SPEs do not require pressure applied to make cathode/anode laminates. Desired SPE characteristics are high ionic conductivity and excellent mechanical properties. The SPE ionic conductivity is strongly correlated to chain segmental motion; thus amorphous polymers with low glass transition temperatures (Tg) are sought.

Figure 1. Schematic concept of the lithium polymer battery. After 3M http://www.rqriley.com/images-spech/img007.jpg

Starting from the nanoscale, we are designing new Li-Ion SPEs that constitute a new approach to high conductivity and processability. These advanced materials are targeted to address the next generation of aerospace applications and space mission needs as shown in Figure 2.

Figure 2. A novel polymer material for use in lithium solid polymer electrolyte batteries. Courtesy NASA Glenn Research Center http://www.derallabs.org/newslink/nl200503_11.html

Equipment

• Scribner Associates fuel cell test station
• Solartron Model 1260 frequency response analyzer and Model 1286 electrochemical interface
• BAS CV-100 potentiostat/galvanostat
• Applied bioPhysics electric cell impedance sensor system