Heteroatom-doped porous carbons derived from lotus pollen for supercapacitors: Comparison of three activators

Abstract

Facile preparation of carbon-based electrode materials with high specific surface area and controllable pore structure through a green and mild strategy is highly desirable for high-performance supercapacitors. Here, hierarchically porous carbon materials were prepared by three types of metal chlorides, including ZnCl2, FeCl3, and CuCl2. Compared with porous carbons obtained by traditional ZnCl2 or FeCl3 activation, hierarchically porous carbon obtained by a facile CuCl2 activation possessed higher yield, larger specific surface area, more developed hierarchical pore structure, and higher heteroatom contents. Benefiting from the synergy of unique morphology, hierarchical pore architecture with abundant micro-/mesopores and coexistence of numerous redox-active nitrogen and sulfur funtionalities, the as-prepared hierarchically porous carbon activated by CuCl2 exhibited superior electrochemical performance in aqueous electrolyte, including a large specific capacitance of 389.3 F g−1 at a current density of 1 A g−1, excellent rate capability and good cycling stability in a three-electrode system. Moreover, the assembled carbon-based symmetric supercapacitor based on CuCl2-activated carbon electrode delivered a significantly increased energy density of 30.4 Wh kg−1 at a power density of 496.0 W kg−1 in comparison to ZnCl2 or FeCl3-activated carbon electrodes. Therefore, CuCl2 activation is proved to be an effective chemical activation agent for the synthesis of biomass-derived carbon materials for high-performance supercapacitors.