Insight into the origin of the positive effects of imidazolium salt on electrocatalytic activity: ionic carbon nanotubes as metal-free electrocatalysts for oxygen reduction reaction.

We report remarkable metal-free electrocatalytic activities of the imidazolium salt-functionalized ionic multi-walled carbon nanotubes (IM-f-MWCNTs) in the oxygen reduction reaction (ORR). The electrocatalytic activity can be attributed to the induced polarization of the π-electrons of CNTs, thus accelerating interfacial electron transfer. The zwitterionic MWCNTs functionalized with poly(vinylimidazolium sulfonate) have a more positive surface charge and exhibit a better electrocatalytic activity than the poly(vinylbutylimidazolium chloride)-functionalized MWCNTs. The IM-f-MWCNTs showed better fuel selectivity than the commercial Pt/C electrocatalyst.