The high-efficiency coupling of a Ni2+ coordinated/uncoordinated pyridine N-COF self-supporting nanofilm as an asymmetric supercapacitor

Abstract

A large-area COF_TAPB–BPY film with a pore size of 3.9 nm was prepared on a gas–liquid interface by the virtue of the limiting and guiding functions of sodium dodecylbenzene sulfonate, followed by modification by Ni²⁺ ions with the reversible redox reaction of Ni(II/III), where Ni²⁺ was evidently anchored on the N in BPY. The obtained COF_TAPB–BPY and Ni-COF_TAPB–BPY nanofilms could avoid the inevitable aggregation and stacking of bulk COF_TAPB–BPY, which facilitated a high specific capacitance of 0.26 mF cm⁻² for the COF_TAPB–BPY nanofilm and 0.38 mF cm⁻² for the Ni-COF_TAPB–BPY nanofilm at 0.001 mA cm⁻². Considering the pseudocapacitance and double-layer capacitance traits of Ni-COF_TAPB–BPY and COF_TAPB–BPY nanofilms, the asymmetric Ni-COF_TAPB–BPY//COF_TAPB–BPY film supercapacitor was assembled with a symmetric COF_TAPB–BPY//COF_TAPB–BPY film device as a control. The asymmetric Ni-COF_TAPB–BPY//COF_TAPB–BPY film supercapacitor could enhance the energy density of 273.9 mW h cm⁻³ at 14.09 W cm⁻³ from 85.2 mW h cm⁻³ at 4.38 W cm⁻³ for the symmetric COF_TAPB–BPY//COF_TAPB–BPY film device. This work provides a new perspective on the application of self-supporting COF nanofilms as film asymmetric supercapacitors.