Graphene-based planar microsupercapacitors are promising energy storage devices for microelectromechanical systems. However, the capacitance and energy density of such graphene-based microsupercapacitors cannot achieve further promotion because of the lack of strategies that permit tailoring both chemical and geometric structures of graphene at the nanoscale. In this study, supercapacitors on hairs with quantum capacitance-dominant extraordinary capacitance are found. Simulations reveal that the record high capacitance and energy density are attributed to the enhanced quantum capacitance effect. The graphene electrodes are prepared by femtosecond laser direct writing-assisted reduction and N-doping of graphene oxides on the human hair surface. Due to the distinct quantum capacitance dominance, the microsupercapacitors exhibit extremely high capacitance (∼3000 mF/cm 2 ) and energy density (∼417 μWh/cm 2 ). We hope that this work will promote the development of microsupercapacitors with high capacitance and energy density.
Utilizing diverse material combinations in heterogeneous structures has become an effective approach for regulating interface characteristics and electronic structures. The g-C 3 N 4 /Co 3 O 4 heterostructures were fabricated by uniformly modifying Co 3 O 4 nanoparticles onto discrete clusters of g-C 3 N 4 nanosheets. Then, they were subsequently employed as positive electrode materials for assembling hybrid supercapacitors. According to the first-principles calculation, Co 3 O 4 and g-C 3 N 4 formed Co-N ionic bonds, establishing interfacial space symmetry-broken heterojunction and direct exchange and superexchange between ions at the interface and sub-interface. This resulted in a high-density spin–orbit hybrid heterogeneous polarization interface, significantly improving the quantum capacitance of heterojunction materials. Experimental results showed that the heterojunction had a specific capacitance of 2662 F g −1 at 1 A g −1 . When the power density was 750 W kg −1 , the energy density reached 128 Wh kg −1 . Even when the power density was 16850 W kg −1 , it could show an energy density of 62.5 Wh kg −1 . The g-C 3 N 4 /Co 3 O 4 heterojunction could realize high energy density charge storage as the cathode material of supercapacitors. The construction of heterogeneous polarization interfaces for high-energy quantum capacitors provides a new and effective method for the energy storage field.
Shun Yang,Zhigang Hao,Shaohua Zhang,Yanjun Gao,Xiangyang Li,Jiong Peng,Lijie Li,Xin Li
An exquisitely designed nanostructure and hybridizing with heteroatom-doped carbon can significantly improve the electrochemical performance of the transition metal sulfides (TMSs). Herein, three-dimensional (3D) hollow N, P, S codoped carbon (NPSC) shells encapsulated with uniformly dispersed cobalt sulfide nanoparticles (Co1–xS/HNPSCS) are synthesized for supercapacitors (SCs) by the sulfuration and carbonization of poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS)-functionalized cobalt-based zeolitic imidazolate framework-67 (ZIF-67). The PZS protects the ZIF-67 from collapsing and convert it in situ into NPSC shells, which are conducive to exposing abundant active sites and accelerating the kinetics of electrochemical reactions. As a result, the Co1–xS/HNPSCS presents an unrivaled specific capacity of 1058.9 C g–1 at 1 A g–1. The assembled Co1–xS/HNPSCS//AC hybrid SC (HSC) demonstrates a remarkable energy density of 57.8 W h kg–1 at a power density of 375 W kg–1. Density functional theory calculations show that the synergy between the Co1–xS and NPSC can optimize the electronic configuration, improve the conductivity, and enhance the adsorption of OH– on the surface of the electrode material. Besides, the quantum capacitance of the carbon layer is also increased by N, P, S codoping. This work exhibits an effective strategy to fabricate TMS/HNPSCS and offers theoretical and methodological guidance for the study of NPSC coating materials.
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