CO2-activated, hierarchical trimodal porous graphene frameworks for ultrahigh and ultrafast capacitive behavior

Herein, we demonstrate CO2-activated macroscopic graphene architectures with trimodal pore systems that consist of 3D inter-networked macroporosity arising from self-assembly, mesoporosity arising from the intervoids of nanosheets, and microporosity via CO2 activation. The existence of micropores residing in hierarchical structures of trimodal porous graphene frameworks (tGFs) contributes to greatly improve the surface area and pore volume, which are ∼3.8 times greater than typical values of existing 3D macroporous graphene monoliths. As confirmed by the specific capacity, the kinetic parameters, and the regeneration capability for chemical adsorption as well as the specific capacitance, the rate capability, and the cycle stability for electrochemical energy storage, the tGFs have an ideal texture for high performance capacitive materials. Furthermore, the tGFs obtain the structurally and energetically homogeneous surface active sites, which dominantly operate through the π-π interactions for adsorption. Consequently, the ultrahigh capacitance and ultrafast capacitive performance of the tGFs for both chemical and electrochemical adsorptions are attributed to hierarchical trimodal porosity and surface chemistry. These results offer a chemical approach combining self-assembly with conventional activation for the construction of 3D hierarchical structures with multimodal porosity.