Synergy effects between single-walled carbon nanotubes and polypyrrole on the electrocatalysis of their composites for the oxygen reduction reaction

To develop the high-efficiency carbon alloy catalysts with significant interaction of C–N, the synergy effects of the polypyrrole/single-walled carbon nanotube (PPy/SWCNT) composites have been studied for the oxygen reduction reaction (ORR) in an alkaline solution. The synergy effects between PPy and SWCNT have been found in the synthesized PPy/SWCNT composites by the characterization using FE-SEM, Raman spectroscopy, XRD, TGA, electrical conductivity, and the electrochemical measurements for the surface area and the electrochemical activities of sites: electron transfer rate, differential capacitance and chemisorbed H-stripping voltammetry. The synergy effects have significantly affected the electrochemical properties of the PPy/SWCNT composites and the electrocatalytic potential at the active sites. The PPy/SWCNT composites synthesized using the electrochemical polymerization method with an identified PPy:SWCNT weight ratio of 1:2 show the best performance of the ORR. For the electrode process on the PPy/SWCNT composites, a mixture of two-electron and four-electron processes occurred. It was found that the synergy effects in the PPy/SWCNT composite electrodes synthesized using the electrochemical polymerization method with a thin net-like PPy film were stronger than those using the chemical polymerization method with a thick shell-like PPy film and played an important role in the ORR electrode kinetics.