Oxygen Reduction Reaction of Block Copolymer Template-Directed Porous Carbon Catalysts

Functional nitrogen-doped hierarchically porous carbon materials (NHPCMs) have received much attention in recent years because of their electrochemical and catalytic activities, which offer potential applications in the field of fuel cells. Herein we demonstrate the NHPCMs with superior performance of the oxygen reduction reaction (ORR) through spontaneous coassembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) micelles along with self-polymerization of dopamine (DA). In this study, we aim to deeply understand the effects of HCl addition, DA content, and aging environment on morphologies of NHPCMs through studying self-assembly and phase behavior of PS-b-PEO/DA mixtures in cosolvent using synchrotron small-angle X-ray scattering and transmission X-ray microscopy. The morphology of hierarchical pores can be successfully obtained by fine controls over DA content and pyrolysis temperature. Correlations of morphologies and processes with the ORR performance indicate that hierarchically porous carbon materials exhibit the highest ORR performance with Jk = 8.1 mA cm-2 (measured at -0.4 V of SCE), low onset potential η = -0.11 V, and four-electron transfer pathway over a wide voltage range.