Role of Graphene Oxide Liquid Crystals in Hydrothermal Reduction and Supercapacitor Performance

Abstract

The formation of liquid crystal (LC) phases in graphene oxide (GO) aqueous solution is utilized to develop high-performance supercapacitors. To investigate the effect of LC formation on the properties of subsequently reduced GO (rGO), we compare films prepared through blade-coating of viscous LC-GO solution and ultrasonic spray-coating of diluted GO aqueous dispersion. After hydrothermal reduction under identical conditions, the films show different morphology, oxygen content, and specific capacitance. Trapped water in the LC GO film plays a role in preventing restacking of sheets and facilitating the removal of oxygenated groups during the reduction process. In device architectures with either liquid or polymer electrolyte, the specific capacitance of the blade-coated film is twice as high as that of the spray-coated one. For a blade-coated film with mass loading of 0.115 mg/cm(2), the specific capacitance reaches 286 F/g in aqueous electrolyte and 263 F/g in gelled electrolyte, respectively. This study suggests a route to pilot-scale production of high-performance graphene supercapacitors through blade-coated LC-GO films.

Achieving High Capacitance of Paper‐Like Graphene Films by Adsorbing Molecules from Hydrolyzed Polyimide

“…Preparation of N-Doped rGO Films: GO was prepared by a modified Hummer's method that was reported previously. [33] The dried GO product was dispersed in aqueous solution at a concentration of 5 mg mL −1 . To this was added, NaCl, (NH 4 ) 2 CO 3 , CH 3 COONH 4 , and powder of a graphene-like porous carbon.…”

“…Though the use of Li 2 SO 4 aqueous electrolyte causes a slight decrease in capacitance when compared to the H 2 SO 4 aqueous electrolyte, the extended voltage window leads to an overall improvement in energy storage, achieving a maximum energy density of 40 Wh kg −1 . This makes the HPI-NG, Li 2 SO 4 device superior to conventional lead-acid batteries (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) Wh kg −1 ) and comparable to Ni-Cd batteries (40-60 Wh kg −1 ), in energy density. The power density of this supercapacitor is in the vicinity of 10 4 W kg −1 , which is 2-3 orders of magnitude higher than that of conventional batteries.…”

A Novel Strategy for Sustainable Synthesis of Soluble‐Graphene by a Herb Delphinium denudatum Root Extract for Use as Light‐Weight Supercapacitors

“…As represented in Figure e, the GCD curves of the D‐graphene supercapacitor electrode at three different current densities were similar in shape and shown an outstanding capacitive behaviour. The ‘C s ’ and power density (P) for the D‐graphene supercapacitor electrode were estimated from the below equations (1‐3) at three different current densities …”

“…The 'C s ' and power density (P) for the D-graphene supercapacitor electrode were estimated from the below equations (1-3) at three different current densities. [68]…”

A Roadmap for Achieving Sustainable Energy Conversion and Storage: Graphene-Based Composites Used Both as an Electrocatalyst for Oxygen Reduction Reactions and an Electrode Material for a Supercapacitor

“…More ions adsorption would happen under a higher degree of reduction in rGO sheets. On the other hand, the LC formation leads to a rumpled morphology of rGO sheets, preventing rGO sheets from restacking and increasing the specific surface area [65].…”