Facile preparation of efficient electrocatalysts for oxygen reduction reaction: One-dimensional meso/macroporous cobalt and nitrogen Co-doped carbon nanofibers

Efficient electrocatalyst for oxygen reduction reaction (ORR) is an essential component for stable operation of various sustainable energy conversion and storage systems such as fuel cells and metal-air batteries. Herein, we report a facile preparation of meso/macroporous Co and N co-doped carbon nanofibers (Co-N-x@CNFs) as a high performance and cost-effective electrocatalyst toward ORR. Co-N-x@CNFs are simply obtained from electro-spinning of Co precursor and bicomponent polymers (PVP/PAN) followed by temperature controlled carbonization and further activation step. The prepared Co-N-x@CNF catalyst carbonized at 700 degrees C (Co-N-x@CNF700) shows outstanding ORR performance, i.e., a low onset potential (0.941 V) and half wave potential (0.814 V) with almost four-electron transfer pathways (n = 3.9). In addition, Co-N-x@CNF700 exhibits a superior methanol tolerance and higher stability (> 70 h) in Zn-air battery in comparison with Pt/C catalyst (similar to 30 h). The outstanding performance of Co-N-x@CNF700 catalysts is attributed to i) enlarged surface area with bimodal porosity achieved by leaching of inactive species, ii) increase of exposed ORR active Co-N-x moieties and graphitic edge sites, and iii) enhanced electrical conductivity and corrosion resistance due to the existence of numerous graphitic flakes in carbon matrix.