Pre-cryocrushing of natural carbon precursors to prepare nitrogen, sulfur co-doped porous microcellular carbon as an efficient ORR catalyst

Abstract A green and facile synthesis of anisotropic 3D architecture high-performance carbon catalyst has been a hot research topic. Herein, a facile and scalable strategy was developed to fabricate an N, S co-doped microcellular carbon from natural polymers of chitosan (N-source) and lignosulfonate (S-source), with the properties enhanced as a result of pre-cryocrushing of natural polymer-based carbon precursors. The as-prepared 3D architecture carbon is mechanically strong and contains cross-linked hierarchical porous micro-sheets and micro-channels. This N and S co-doped carbon, prepared from pre-cryocrushing of chitosan (60%) and lignosulfonate (40%) precursor (NSC/CC-C/L (60/40)), annealed at 900 °C shows unique structures, with significant defects, rough edges, rich micro/meso-pores, large surface area, N and S doping, and high pyridinic-N and thiophene-S contents. The NSC/CC-C/L (60/40)-900 sample exhibits superior performance with favorable kinetics, methanol resistance, and excellent durability as an ORR catalyst, all of which are much better than a commercial Pt/C and most reported metal-free catalysts. Impressively, the onset potential of the NSC/CC-C/L-900 sample reaches 1.08 V (vs. reversible hydrogen electrode) and the half-wave potential is 0.98 V, which are compared to 1.02 and 0.92 V for Pt/C.