The air electrode, which reduces oxygen (O2), is a critical component in energy generation and storage applications such as fuel cells and metal/air batteries. The highest current densities are achieved with platinum (Pt), but in addition to its cost and scarcity, Pt particles in composite electrodes tend to be inactivated by contact with carbon monoxide (CO) or by agglomeration. We describe an air electrode based on a porous material coated with poly(3,4-ethylenedioxythiophene) (PEDOT), which acts as an O2 reduction catalyst. Continuous operation for 1500 hours was demonstrated without material degradation or deterioration in performance. O2 conversion rates were comparable with those of Pt-catalyzed electrodes of the same geometry, and the electrode was not sensitive to CO. Operation was demonstrated as an air electrode and as a dissolved O2 electrode in aqueous solution.

A new synthetic route to poly-3,4-ethylenedioxythiophene (PEDT) with a conductivity exceeding 1000 S/cm is described. The method is based on base-inhibited vapor-phase polymerization, where a surface covered with ferric p-toluenesulfonate as oxidant mixed with a volatile base (pyridine) is exposed to 3,4-ethylenedioxythiophene (EDT) vapors. The base is added to suppress an acid-initiated polymerization of EDT, leading to a product with little or no conjugation. The product of the base-inhibited vapor-phase polymerization is confirmed to be virtually identical to PEDT obtained by wet chemical oxidation by both spectroscopic and electrochemical methods. A possible reaction scheme for the acid-initiated polymerization is discussed.

Vapor phase polymerization is a versatile technique that can be used to obtain highly conducting coatings of conjugated polymer on both conducting and nonconducting substrates. This is demonstrated here by preparation of polypyrrole, polybithiopene, and polyterthiopene, coatings that otherwise must be prepared electrochemically in order to achieve the desired high conjugation. The method is based on the use of organic ferric sulfonates as oxidant as these salts easily form smooth, noncrystalline films. By proper choice of the sulfonate anion, the oxidizing power of the ferric salt can be varied over a wide range. The described technique can easily be adapted to different patterning techniques.