Co-NC catalyst with rich coordinated nitrogen and hierarchical porous structure for oxygen reduction reaction

Abstract

Cobalt nitrogen-doped carbon (Co-NC) catalysts are synthesized for oxygen reduction reaction (ORR) via the pyrolysis of zinc-mediated and SiO2-templated 2,6-diaminopyridine (DAP) composites. The resulting Co-NC(Zn12-SiO2[20])-900 demonstrates exceptional ORR activities, with half-wave and onset potentials of 0.835 V and 0.875 V, respectively, which is similar to Pt/C catalyst. In long-term durability test, the Co-NC(Zn12-SiO2[20])-900 catalyst exhibits a negligible E1/2 shift, and in methanol tolerance tests, it displays significantly better performance than commercial Pt/C catalyst. The superior performance can be attributed to the hierarchical porous structure, dense and highly accessible Co-N4 and graphitic nitrogen (g-N) sites. The high content of Co-N4 and g-N sites enhances 3d-orbital filling and reduces the Co centers' on-site magnetic moment, as calculated by density functional theory. This may lead to a decrease in the energy barrier of the rate-determining step (RDS), which in turn enhances the intrinsic activity of the ORR.