Direct synthesis of interconnected N, S-codoped porous exfoliated carbon nanosheets as advanced electrocatalysts for oxygen reduction reaction

Abstract

The pursuit of porous carbonaceous materials with large specific surface area, well-defined pore structure and desirable dopants remain challenges for both energy storage and conversion. Here, we fabricate a novel interconnected N, S-codoped porous exfoliated carbon nanosheets (ECNs) with large specific area and pore volume through a one-step carbonization process by using glucose/melamine-sulphate-salt (GMSS) as precursor. By carefully examining the carbonization process of the precursor, we propose a phase separation mechanism for the formation of ECNs. The optimized sample, composed of interconnected thin graphite layers with N and S co-doping in the carbon lattice, exhibits outstanding ORR activity in terms of half-wave potential (0.83 V vs. RHE) and onset potential (0.97 V vs. RHE), together with 4-electron selectivity (H2O2 yield less than 8%), one of the best among all reported metal-free ORR catalysts.