N, S Co-Doped Porous Carbon with High Capacitive Performance Derived From Heteroatom Doped Phenolic Resin

Abstract

Introducing fast pseudo-capacitance is an effective strategy to improve the capacitive performances of carbon-based materials. Here, thiourea is used as nitrogen and sulfur sources to dope resorcinol formaldehyde polymer. In the polymerizing process, the formed thiourea resin acts as template to adjust the hierarchical microstructure besides that the copolymer is formed by reacting thiourea and resorcinol with formaldehyde. After being carbonized and activated, the N and S co-doped carbon with high specific surface area of 3599.0 m2 g-1 is obtained. Benefiting from the large specific surface area, developed porosity and the multiple functional groups, the specific capacitance of the optimized sample can reach to 461.5 F g-1 in 6.0 mol L-1 KOH electrolyte at current density of 0.1 A g-1. Furthermore, when the current density is as high as 20.0 A g-1, the specific capacitance can still retain 293 F g-1, indicting good rate capability. The assembled symmetric device exhibits the maximum energy density of 14.9 Wh kg-1 at the power density of 61.9 W kg-1 based on the active materials. After 10000 cycles tested at current of 20.0 A g-1, the capacitance can retain 97.4 % of the initial capacitance, demonstrating its good long-term cyclic stability. This co-doped strategy provides an effective approach to prepared carbon-based materials with high capacitive performance.