Advanced Functional Carbons and Their Hybrid Nanoarchitectures towards Supercapacitor Applications

Porous carbons have attracted much attention as electrode materials for supercapacitors due to their enormous surface area, high electrical conductivity, excellent corrosion resistance, high temperature stability, and relatively low cost. The design of porous architectures is considered key for determining electrochemical performance. Pore size distribution, pore size, and pore connectivity strongly affect electrochemical performance. Various carbon materials with pore size ranging from micro- to macropores were extensively studied. Herein, various types of porous carbon-based and hybrid materials from different approaches and their electrochemical applications are summarized. Appropriate tuning of the pore size of carbon materials is essential for ensuring good transport of ions with different sizes throughout the electrolyte, so that the electrode materials can be fully utilized. Many carbon materials were produced from a series of carbonization and activation processes that possess controllable pore structures, including activated carbons, graphite, carbon nanotubes, carbon aerogels, and templated porous carbons. Templated carbon materials were prepared by various approaches, such as direct carbonization from carbon precursors and soft- and hard-template methods. To enhance the electrochemical performance of the electrode materials, heteroatoms, such as nitrogen, sulfur, and boron, were doped into porous carbons. In addition, to optimize the overall capacitance without destroying the stability and morphology of electrode materials, pseudocapacitive materials, such as transition-metal oxides, were introduced into the carbon frameworks. In this review, recent advances in the fabrication of nanoarchitectured porous carbons and metal oxides through various approaches for supercapacitor applications are summarized.