A renewable bifunctional structural supercapacitor using the recycled geopolymer membrane and MnO2/CNTs electrode

Abstract

A bifunctional supercapacitor based on the recycled montmorillonite geopolymer membrane and MnO₂/CNTs composite electrodes was designed and assembled. The recycled geopolymer was prepared from recycled montmorillonite geopolymer powder and alkali activators and used as a solid electrolyte skeleton, with a maximum compressive strength of 30.6 MPa after 28 days of curing, which is comparable to the strength of the initially polymerized geopolymer. The MnO₂/CNTs electrodes were prepared by electrodeposition method, and the electrode materials containing 2 wt% CTAB and 1 wt% CNTs had the best area specific capacity of 3310 mF cm⁻² at a current density of 1 mA cm⁻². The regenerated geopolymer electrolyte framework was injected with 0.5 M Na₂SO₄ and assembled with MnO₂/CNTs electrode to form a structural load-bearing supercapacitor, which had a specific capacity of 2094.4 mF cm⁻² at a load of 15 MPa, with a capacity retention rate of 65.43 % after 10,000 charge/discharge cycles.