Design of bifunctional sandwich-like Co@Si/Ox-MXene nanocomposite to increase the supercapacitor properties and removal of pollutants from wastewater

Spent supercapacitor electrodes are considered waste after the end of the cycle. Designing a multifunctional material to increase the specific capacity of supercapacitors and eliminate environmental pollution is one of the existing challenges. In this study, Co3O4 was extracted from waste CMB by several tandem hydrothermal methods. Also, 3-Aminopropyl-triethoxysilane (APTES) was used to exfoliate and surface modification of Ti3C2Tx MXene nanosheets. Then, by assembling Co3O4 on the synthesized Ti3C2Tx nanosheet, a sandwich composite of Co@Si/Ox-Ti3C2Tx was formed through the formation of a complex with active surface functional groups on the oxalic acid modified MXene surface. Co3O4 can increase the number of redox reaction sites and fast charge transfer in the conducting channels of MXene by penetrating interlayers. The Co@Si/Ox-Ti3C2 composite electrode showed an increased specific capacity of 1821 Cg -1 at a current density of 1 Ag-1. The prepared hybrid supercapacitor (HSC) with Co@Si/Ox-Ti3C2 composite as the positive electrode and silanized active nanocarbon (Si69@AC) with bis(triethoxysilylpropyl)tetrasulfide as the negative electrode had a high energy density of 50 Wh kg - 1 up to a power density of 8422 W kg - 1 along with excellent cyclic life of 90.87% capacitance retention. After 15,000 cycles, XRD and XPS analyses confirmed 62% degradation of the positive electrode and conversion to TiO2 after 30 days in water. To graft the separated and agglomerated elements, they were added to the TEOS solution and subjected to the sol-gel process. High photocatalytic properties, 97% degradation of methylene blue (MB), changing the absorption region from UV to visible due to changing its band gap to 3.3 eV were among the characteristics of the new material. This work is a new approach for the construction of ecofriendly new HSCs.