Nitrogen-doped carbon sponge derived from the self-assembly of poly(amic acid) for high performance oxygen reduction reaction

Abstract

Nitrogen-doped carbon materials with highly porous structures and interconnected ultrathin frameworks have shown outstanding features for electrocatalytic applications. Herein, we propose a self-assembly strategy to prepare nitrogen-doped carbon sponge (NCS) with high porosity, an ultrathin framework, and a high content of active nitrogen species for high performance oxygen reduction reaction (ORR) by direct pyrolysis of the polymeric precursor. Amphiphilic poly(amic acid) (PAA) can self-assemble into a highly porous sponge-like structure (donated as PAA sponge). After pyrolysis, the high porosity and ultrathin framework of the PAA sponge are well inherited. The nitrogen species in the PAA sponge convert to pyridinic and graphitic nitrogen when pyrolyzed at 800 °C to give NCS-800, corresponding to an atomic percent of 4.6%, which are believed to be the origin of ORR catalytic activity. The NCS-800 shows high catalytic performance toward the ORR and superior methanol tolerance and long-term stability in comparison to Pt/C. After 30 hours, the relative current density is still as high as 92.4%, which is much higher than that of Pt/C (73.7%). This strategy can be extended to facilely prepare doped carbon materials with tailored morphologies and heteroatom species by choosing appropriate monomers from the abundant library of diamines and dianhydrides.