Triphenylene-derived oxygen-enriched hierarchical porous carbon nanosheets: Carbonization mechanism and application in zinc-ion hybrid capacitors

Since zinc-ion hybrid capacitor (ZIHC) was first proposed, it has become an international study hotspot in the field of secondary energy for some time. Unfortunately, the unsatisfactory specific capacity of ZIHCs has limited its application in industrial development. Thus, there is an urgent need to synthesize carbon cathode with abundant pore structure and heteroatoms to construct high performance ZIHCs. Herein, we investigate the mechanism of FeCl3-induced carbon formation of triphenylene using FeCl3 as a catalyst and template. And the oxygen-enriched hierarchical porous carbon nanosheets with large specific surface area and abundant pores are successfully synthesized with the assistance of KOH activation strategy. Due to the addition of FeCl3 and KOH, the hierarchical porous carbon nanosheets have a unique pore structure and extremely high pore volume, and oxygen atoms are introduced to provide additional pseudocapacitance. As expected, ZIHCs constructed with the best sample exhibits an impressive specific capacity of 134.1 mAh g−1, a distinguished energy density of 102.04 Wh kg−1 (80 W kg−1) and outstanding cycling stability. This work clearly elucidates the carbon formation mechanism of triphenylene under the catalytic action of FeCl3, and provides another insight for the preparation and optimization of porous carbon for ZIHCs cathode.