Synthesis and Characterization of Nitrogen-Doped Ordered Mesoporous Hollow Carbon Spheres for the ORR

Abstract

This work presents the synthesis by a silica template-based method of metal-free electrocatalyst for the Oxygen Reduction Reaction (ORR) for alkaline fuel cells. Nitrogen-doped Ordered Mesoporous Hollow Carbon Spheres (N-OMHCS) was obtained starting from a SiO2 template. The N-OMHCS material has been functionalized with methanol using the intermittent microwave heating technique to produce the N-OMHCS-f electrocatalyst. Then, the catalytic activity of N-OMHCS and N-OMHCS-f electrocatalysts were evaluated for the ORR in 0.5 mol L-1 KOH, with the rotating ring-disk electrode technique (RRDE). The electrochemical results indicate that N-OMHCS-f has higher catalytic activity for the ORR than N-OMHCS, whit an onset potential of 0.81 and 0.82 V vs. RHE and a limiting current of -3.6 and -2.3 mA cm-2, respectively. On the other hand, both electrocatalysts produce about the same amount of H2O2 (between 14 and 26 %). The catalytic activity of N-OMHCS and N-OMHCS-f can be attributed to the nitrogen species on their surface and their porous structure, which provides a triple phase region promoting the adsorption-desorption of O2.