8-Hydroxyquinoline-5-sulfonic acid on reduced graphene oxide layers as a metal-free electrode material for supercapacitor applications

Asymmetric Supercapacitors based on 1,10-phenanthroline-5,6-dione Molecular Electrodes Paired with MXene

An efficient approach to increase the energy density of supercapacitors is to prepare electrode materials with larger specific capacitance and increase the potential difference between the positive and negative electrodes in the device. Herein, an organic molecular electrode (OME) is prepared by anchoring 1,10-phenanthroline-5,6-dione (PD), which possesses two pyridine rings and an electron-deficient conjugated system, onto reduced graphene oxide (rGO). Because of the electron-deficient conjugated structure of PD molecule, PD/rGOs exhibit a more positive redox peak potential along with the advantages of high capacitance-controlled behaviour and fast reaction kinetics. Additionally, the small energy gap between the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) leads to increased conductivity in PD/rGO. To assemble the asymmetric supercapacitor (ASC), a two-dimensional metal carbide, as known as MXene, with a chemical composition of Ti3C2Tx is selected as the negative electrode due to its exceptional performance, and PD/rGO-0.5 is employed as the positive electrode. Consequently, the working voltage is expanded up to 1.8 V. Through further electrochemical measurements, the assembled ASC (PD/rGO-0.5//Ti3C2Tx) achieves a remarkable energy density of 36.8 Wh kg-1. Remarkably, connecting two ASCs in series can power 73 LEDs, showcasing its promising potential for energy storage applications.

One-pot solvothermal incorporation of graphene into chain-engineered polyquinones for metal-free supercapacitors

Solvothermal reduction of graphene oxide and Schiff-base condensation between anthraquinone and dialdehydes were simultaneously performed to produce well-dispersed composites as metal-free supercapacitor electrodes, which rationally combine conductive graphene and pseudocapacitive polyquinones that allow for fast electron/ion transport and efficient redox reactions, affording great rate capability and high power/energy densities.

Graphene covalently functionalized with 2,6-diaminoanthraquinone (DQ) as a high performance electrode material for supercapacitors

2,6-Diaminoaquinone molecules were covalently modified onto the surface of GO via a nucleophilic displacement reaction between the epoxy groups on the surface of GO and the –NH₂ groups of DQ molecules in the presence of ammonia to form a composite material.