Background

Fuel cells offer the promise of a clean energy source for stationary power generation. They produce energy from hydrogen, natural gas, alcohol, or other readily available hydrocarbon fuels. Fuel cells date back to the nineteenth century when Grove, in 1839, first published his work on the generation of electricity by partially immersing two platinum electrodes and separately supplying oxygen and hydrogen to them.1 There is considerable current interest in fuel cells as an environmentally clean alternative to fossil-fuel-burning power sources.
Catalysts for Fuels Cells

Platinum is the most common catalyst for fuel cells; however, due to its high cost it is often doped with palladium, ruthenium, cobalt/nitrogen complexes, or more recently iridium or osmium. In addition to its high cost, platinum is also quite rare. In fact, there is not enough platinum in the world to equip every vehicle in use today with a traditional (Pt-catalyst) proton exchange membrane (PEM) fuel cell. For this reason, new catalysts, doped-platinum catalysts, and new platinum-deposition techniques are all being developed to reduce the amount of platinum needed for fuel cell catalysts.
Conducting Polymers

The discovery over twenty five years ago of relatively high electrical conductivity (~103 S/cm) of doped polyacetylene sparked extensive research in the application of conjugated polymers in such diverse fields as electronics, energy storage, catalysis, chemical sensing, biochemistry, and corrosion control. Unfortunately, the conducting polymers were found to be unstable in air and difficult to process. Significant advances in improving the desired electrical, optical, and mechanical properties, while simultaneously enhancing processability and stability, have been realized by cross-disciplinary collaborations between chemists, physicists, materials scientists, and engineers.
Polyaniline

Polyaniline is becoming the conducting polymer of choice in many applications for several reasons: its electronic properties are readily customized; it exhibits excellent chemical stability, and is the least expensive of the conducting polymers.
Polythiophenes

Polythiophenes have been studied extensively for use in light emitting diodes, among other applications, due to the chemical variability offered by substitution at the 3- and 4- positions. The regularity of the side-chain incorporation strongly affects the electronic band gap of the conjugated main chain and is critical to device performance. Sigma-Aldrich offers highly regiocontrolled alkylsubstituted polythiophenes (P3AT): almost completely regioregular head-to-tail (HT) P3AT and regiorandom (1:1 HT/HH) P3AT.10
Solid Polymeric Electrolytes (SPE)

NASA's jet propulsion laboratory is currently investigating SPEs formed by reacting lithium salts (e.g. LiClO4, LiPF4, and LiCF3SO3) with cyanoresins for rechargeable batteries and electrochemical cells. Specifically, SPEs would be used as separators between carbon composite anodes and cathodes. It has been proposed that these batteries would have an energy density of 80 W.h.lb-1 and be viable for 1000 recharge cycles. Polyacrylonitrile, polyvinyl pyrrolidone, and polyethylene have dielectric constants between 4 and 5 and lithium-ion conductivities between 10-6 and 10-5 S.cm-1. Unfortunately these room-temperature conductivities are too low for effective power generation. SPE's formed from amorphous cyanoresins such as cyanoethyl polyvinyl alcohol (CRV), cyanoethyl pullulan (CRS), and cyanoethyl sucrose (CRU) have dielectric constants as high as 20 or more and lithium-ion conductivities 100 times greater than conventional SPEs.
Nafion Resins

Sigma-Aldrich also carries a complete line of Nafion® resins. Nafion® resins are perfluorinated ion-exchange materials composed of carbon-fluorine backbone chains and perfluoro side chains containing sulfonic acid groups. Solid polymer fuel cells for pulse power delivery are based on Nafion® solid polymeric electrolytes.