N, S-containing MOF-derived dual-doped mesoporous carbon as a highly effective oxygen reduction reaction electrocatalyst

Abstract

Nitrogen, sulfur-codoped carbon catalysts with enriched mesopores were, for the first time, synthesized by pyrolyzing a novel N, S-containing MOF, viz. [Zn₂(TDC)₂(DABCO)]·4DMF (SCUT-12, TDC = 2,5-thiophenedicarboxylic acid, DABCO = 1,4-diazabicyclo[2.2.2]octane). Single-crystal X-ray diffraction reveals that the S-containing ligand (TDC) and N-containing ligand (DABCO) are regularly crystallized into the SCUT-12 framework, which act as internal sulfur and nitrogen sources. As such, the two dopant atoms can be uniformly introduced into one precursor at the molecular level, and the codoping of two elements can be achieved in one step during carbonization, simplifying the conventional protocol. Structural characterization reveals that the resultant carbon is mesoporous and has high specific surface area, which favors the exposure of electrocatalytic active sites and mass transfer of the reactive species. As a result, the N, S-codoped carbon pyrolyzed at 900 °C (NSMC-900) shows a decent activity towards the oxygen reduction reaction (ORR) with an onset and half-wave potential up to 0.98 and 0.85 V, respectively, which are comparable with those of a 40 wt% commercial Pt/C catalyst. NSMC-900 also shows a superior long-term stability to Pt/C. Finally, it is found that the dual element-doped carbon outperforms either one of the mono-element-doped carbons, demonstrating the favorable synergistic effect of dual element-doping.