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 J
k = 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.