Fabrication of complex, 3D, branched hollow carbonaceous structures and their applications for supercapacitors

Sodium carboxymethylcellulose/MXene/zeolite imidazolium framework-67-derived 3D porous carbon aerogel for high-performance asymmetric supercapacitors

Herein, we propose a carbon/TiO2/Co3O4 (CTC) composite carbon aerogel with a 3D porous conductive network structure derived from sodium carboxymethylcellulose (CMC)/Mxene (Ti3C2Tx)/zeolite imidazolium framework-67 (ZIF-67). Among them, CMC is used as the carbon skeleton, which can reduce the powdering caused by volume change and improve the cycle stability. Ti3C2Tx acts as the conductive agent and dispersant for ZIF-67, exposing more reactive sites while constructing fast conductive channels to enhance electrochemical performance. The microstructure of the CTC carbon aerogel is modulated by controlling the mass ratio of Ti3C2Tx to ZIF-67, and the carbon aerogel with a mass ratio of 2:3 (CTC-2:3) is experimentally demonstrated to have the best electrochemical performance. The CTC-2:3 electrode exhibits a high specific capacitance of 481.7 F g-1 at 1 A g-1 and possesses a rate performance of 78.9 % at 10 A g-1. The assembled asymmetric supercapacitor (ASC, CTC-2:3//Ti3C2Tx) delivers an energy density of 48.4 Wh kg-1 at a power density of 699.8 W kg-1. Moreover, the ASC device maintains 85.3 % initial capacitance and 99.1 % coulombic efficiency after 10,000 GCD cycles, indicating good cycling stability. This facile design pathway provides a new insight for the development of high-performance electrode materials.

Superstructures of Zeolitic Imidazolate Frameworks to Single- and Multiatom Sites for Electrochemical Energy Conversion

The exploration of electrocatalysts with high catalytic activity and long-term stability for electrochemical energy conversion is significant yet remains challenging. Zeolitic imidazolate framework (ZIF)-derived superstructures are a source of atomic-site-containing electrocatalysts. These atomic sites anchor the guest encapsulation and self-assembly of aspheric polyhedral particles produced using microreactor fabrication. This review provides an overview of ZIF-derived superstructures by highlighting some of the key structural types, such as open carbon cages, 1D superstructures, hollow structures, and the interconversion of superstructures. The fundamentals and representative structures are outlined to demonstrate the role of superstructures in the construction of materials with atomic sites, such as single- and dual-atom materials. Then, the roles of ZIF-derived single-atom sites for the electroreduction of CO₂ and electrochemical synthesis of H₂ O₂ are discussed, and their electrochemical performance for energy conversion is outlined. Finally, the perspective on advancing single- and dual-atom electrode-based electrochemical processes with enhanced redox activity and a low-impedance charge-transfer pathway for cathodes is provided. The challenges associated with ZIF-derived superstructures for electrochemical energy conversion are discussed.