Copolycondensation of heterocyclic aldehydes: A general approach to sulfur and nitrogen dually-doped carbon gels

• S/N-doped carbon gels are obtained by copolycondensation of heterocyclic aldehydes.
• The amount of S- and N-doping can be precisely controlled.
• During gel carbonization S is lost as carbon-containing gases (CS2 and OCS).
• Presence of the thiophenic –C–S–C– moiety enhances the specific SBET surface area.
• Presence of the pyrrolic –C–N–C– moiety enhances development of ultramicroporosity.

Recent research concerning heteroatom-doped carbon materials reveals strong evidence of the superior electrochemical performance of S, N-dually doped carbons over their mono- or multidoped counterparts enriched with different elements. Herein sulfur and nitrogen co-doped carbon gels produced via sol–gel copolycondensation of a mixture of S- and N-containing heterocyclic aldehydes with resorcinol are presented and examined for the first time. The characteristics of the carbonaceous materials can be tuned by means of the initial ratio of the aldehydes (control of the S and N content, control of the texture), sol–gel synthesis conditions (control of morphology) and carbonization conditions (control of texture, amount of doped heteroatoms, their chemical state and the structure of the carbon framework). The S, N-co-doped carbon gels obtained are characterized by specific surface areas of up to 570 m2/g, maximal S and N content of up to 14 and 9 wt%, respectively, and a peculiar correlation between the amount of S- and N-doping, carbonization temperature and the development of micro- and ultramicroporosity.

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