Core-Shell Multiwalled Carbon Nanotube/Cobalt Corrole Hybrids for the Oxygen Reduction Reaction

The development of hybrid nanomaterials that preserve and combine the properties of their constituents is a central issue of nanosciences. Herein, we describe the polymerization via coppercatalyzed azide-alkyne cycloaddition (CuAAC) of cobalt(III) corroles around conductive carbon nanotubes to produce chemically robust hybrid catalysts for the oxygen reduction reaction (ORR). A combination of techniques including UV-vis-NIR absorption, Raman and X-ray photoelectron spectroscopies (XPS), and scanning electron microscopy (SEM) was used to characterize the assembly of the two parts of the functional hybrid system for which the activity and the selectivity toward the ORR process in acidic media are obtained by a combination of rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) measurements. The polymerized hybrid (click MWNT-CoCorr) exhibits an overpotential of ca. 230 mV compared to a reference platinum ink; the number of electrons involved in the reduction of oxygen is close to 3 in acidic media, demonstrating that the corrole cobalt centers in the hybrids reduce oxygen via a mixed pathway of twoand four-electrons.