Hybrid PEDOT/MnOx nanostructured electrocatalysts for oxygen reduction

Abstract

A series of hybrid poly(3,4-ethylenedioxythiophene)/manganese oxide (PEDOT/MnO_x) thin films have been prepared via a stepwise approach: electrodeposition of PEDOT, followed by formation of MnO_x particles by a spontaneous redox reaction between PEDOT and KMnO₄. Electrocatalytic characterization of the PEDOT/MnO_x thin films demonstrates high activity toward the oxygen reduction reaction (ORR), with a shift in intrinsic ORR onset and half-wave potentials by ca. 0.2 V to lower overpotential relative to the PEDOT thin film. The most active PEDOT/MnO_x thin film electrocatalyst, P-MnO_x-20, demonstrates superior activity relative to the commercial 20% Pt/C catalyst in the half-wave region of the ORR potential window at equal mass loading, with a half-wave potential of 0.83 V (20% Pt/C, 0.81 V) and charge transfer resistance of 479 Ω (20% Pt/C, 862 Ω). The P-MnO_x-20 film also demonstrates preference to a pseudo-four electron ORR pathway (n = 3.8) and high specific ORR activity, when considered on both a total mass (−96 mA mg_total⁻¹; 20% Pt/C: −108 mA mg_total⁻¹) and metal (or metal oxide) mass basis (−296 mA mg_MnOx⁻¹; 20% Pt/C: −540 mA mg_Pt⁻¹). The P-MnO_x-20 film has been identified as the most active PEDOT/ceramic composite electrocatalyst reported to date, which is rationalized by the high surface concentration of Mn^(III), strong electronic coupling between PEDOT and MnO_x, as well as a high active site density and efficiency achieved by the stepwise electrodeposition-redox approach.