Dual-Doping of Sulfur on Mesoporous Carbon as a Cathode for the Oxygen Reduction Reaction and Lithium-Sulfur Batteries

Mesoporous carbon derived from pyrolysis of metal-organic frameworks (MOFs) is advantageous owing to its high specific surface area, large pore volume, and versatility in both structure and composition. Heteroatom doping on mesoporous carbon by synthesizing with heteroatom containing ligands (pre-synthetic process) or incorporating heteroatom-containing compounds during pyrolysis (post-doping) can further enhance its electrochemical properties. Although both methods have been applied to increase the doping content, the effects of the pre-synthetic process and post-doping have not yet been systematically studied. Herein, we have synthesized mesoporous carbon derived from sulfur-containing MOFs for the first time using 2,5-disulfanylterephthalic acid as a ligand and added dopants (melamine for N-doping and thiourea for N,S-codoping). We systematically compared the performance of mesoporous carbon as cathodes for the oxygen reduction reaction (ORR) and lithium-sulfur (Li-S) batteries with previous studies, which used terephthalic acid and its analogues as pre-synthetic ligands and various dopants as post-doping sources. Our work showed the synergetic effect of heteroatoms from dual-doping process - especially sulfur (S from pre-synthetic process and N,S from post-doping), which not only enhanced catalytic activity (limiting current density (JL) of -5.19 mA·cm-2), stability, and methanol tolerance as an ORR catalyst but also rendered superior stability of 85.2% over 100 cycles as a cathode of Li-S batteries.