(544hb) Electrocatalytic Activity of Thin Polymeric Films Synthesized through Chemical Vapor Deposition

Electrocatalytic reduction of oxygen is a key reaction in some of the most promising energy conversion devices, such as fuel cells and metal-air batteries. Reports on the activity of poly(3, 4 ethylenedioxythiophene) (PEDOT) in oxygen reduction reaction (ORR) have been widely discussed^1,2, yet no clear explanation for the observed activity of PEDOT in ORR has been offered. Here, we studied ORR activity of PEDOT synthesized through oxidative Chemical Vapor Deposition (oCVD). Using oCVD, we synthesized conjugated polymeric films using a single-step, solvent-free approach. The effects of different dopants, oxidants, film thickness and reaction conditions on the ORR activity of the deposited material were investigated. We showed that thin films of PEDOT facilitate oxygen reduction activity and show performance comparable to that of platinum. Deposited PEDOT films reduce overpotential up to 230 mV and enhance the current density up to 51% when compared with the glassy carbon electrode. As the PEDOT film thickness increased, the double layer effect and the charge storage in the polymeric film obscure the signal. We estimated the electron transfer number for oxygen reduction on PEDOT films using Rotating Disk Electrode (RDE); the result indicates that the direct pathway with n~4 is the most plausible pathway in alkaline media. In addition, we observed that our CVD processing condition, and more specifically temperature of the surface, has a direct effect on conductivity of the deposited films. We deposited films with conductivity as high as 2000 S/cm.

• Khomenko, V. G., V. Z. Barsukov, and A. S. Katashinskii. "The catalytic activity of conducting polymers toward oxygen reduction." Electrochimica Acta7-8 (2005): 1675-1683.
• Winther-Jensen, Bjorn, et al. "High rates of oxygen reduction over a vapor phase–polymerized PEDOT electrode." Science5889 (2008): 671-674.