Copper doped CoSx@Co(OH)2 hierarchical mesoporous nanosheet arrays as binder-free electrodes for superior supercapacitors

Heteroatom doping is an effective route to boost the capacitance performance of metal sulfides-based electrode materials. Herein, an array of hierarchical 3D mesoporous Cu doped CoSx@Co(OH)(2) nanosheets (namely Cu/CoSx@Co(OH)(2)) is successfully prepared on Ni foam through a metal-organic-framework (MOF) mediated approach. The combination of compositional merits and tuned electronic properties induced by copper doping leads to superior capacitance performance. The optimal Cu doped electrode (Cu/CoSx@Co (OH)(2)-2) displays an ultrahigh specific capacitance and outstanding rate capability, which outperforms the best values obtained on other transition metal sulfide (TMS) electrodes. And the Cu/CoSx@Co(OH)(2)-2//ac-tivated carbon (AC) asymmetric two-electrode supercapacitor device exhibits a favorable energy density of 39.25 Wh kg(-1) and outstanding cycle life. X-ray photoelectron spectroscopy (XPS) results reveal that the greatly decreased binding energy barriers of two redox pairs (Co2+/Co3+ and Cu+/Cu2+) are beneficial to higher electrochemical performance. Density function theory (DFT) results further disclose the Cu-doping effect and the benefit of nanocomposite formation on the energy storage performance. The results provide an inspiration to the optimization of TMS-based electrodes for high performance electrochemical energy storage systems.(C) 2022 Elsevier B.V. All rights reserved.

Automated summary

Heteroatom doping is an effective approach to enhance the capacitance performance of metal sulfides-based electrode materials. In this study, hierarchical 3D mesoporous Cu doped CoSx@Co(OH)(2) nanosheets are successfully prepared through a metal-organic-framework mediated method, which exhibit superior capacitance performance due to the combination of compositional merits and tuned electronic properties induced by copper doping. The optimal Cu doped electrode shows ultrahigh specific capacitance and outstanding rate capability, surpassing other transition metal sulfide electrodes. Additionally, the asymmetric two-electrode supercapacitor device based on Cu/CoSx@Co(OH)(2)-2//activated carbon demonstrates favorable energy density and cycle life.