Manganese Oxide/Poly(3,4-ethylenedioxythiophene) Hybrid Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Fuel Cells

Abstract

Manganese oxide/poly(3,4-ethylenedioxythiophene) (MnOx/PEDOT) nanostructured hybrid thin films are readily prepared using a simple anodic electrodeposition process from aqueous solution. Using this approach, MnOx/PEDOT films with thicknesses and mass loadings up to 100 nm and 40 μg cm-2 were prepared, then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnOx/PEDOT provided improvements over MnOx-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials and > 1.5 times increase in current density. The MnOx/PEDOT film exhibited only a slightly lower reaction order (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnOx/PEDOT also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. The high activity and synergism of MnOx/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact and the improved charge transfer processes attained by co-electrodepositing MnOx with PEDOT. PEDOT has previously been demonstrated in fuel cells to limit methanol crossover. PEDOT has also been used as a catalyst support in fuel cells. These facts, combined with the substantially lower cost of Mn versus Pt (Mn is ~ 17,000 times cheaper), augurs for further development and testing of MnOx/PEDOT hybrid materials as ORR electrocatalysts with application in alkaline fuel cells. This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.