Improved supercapacitor performance of MnO2–graphene composites constructed using a supercritical fluid and wrapped with an ionic liquid

Abstract

Supercritical CO 2 (SCCO 2 ) is used to synthesize MnO 2 . This process is found to be promising for producing oxide nanorods ($5 nm in diameter) with little agglomeration. With suitable SCCO 2 pressure and temperature, nanocrystalline a-MnO 2 with an extremely high surface area of 245 m 2 g À1 (versus 80 m 2 g À1 for the oxide prepared in ambient air) was obtained. Introduction of graphene nanosheets and carbon nanotubes into MnO 2 with and without the aid of SCCO 2 is compared. SCCO 2 can help debundle the graphene nanosheets and uniformly disperse the MnO 2 nanorods in between, thus preventing graphene restacking. Since the oxide particles are sandwiched between the highly conductive sheets, a high electrochemical utilization is obtained. Accordingly, SCCO 2 -MnO 2 /graphene shows superior supercapacitor properties. The feasibility of using an ionic liquid (IL) as a conductive wrapping agent to improve the performance of the MnO 2 /graphene electrode is demonstrated.Because the intimate contact between the oxide and graphene can be ensured and the interfacial double-layer capacitance can be optimized, the electrode wrapped with an IL shows a higher capacitance, improved high-rate capability, and higher cyclic stability compared to those obtained without IL wrapping.

Cost‐Effective Hierarchical Catalysts for Promoting Hydrogen Release from Complex Hydrides

“…[44,45] To decorate Ni nanoparticles onto Fe/CNTs, nickel(II) acetylacetonate (10 mg;S igma-Aldrich;9 9.9 %) and Fe/CNTs( 40 mg) were loaded into a5 00 mL stainless steel autoclave. The graphene nanosheets were prepared using am odified Staudenmaier method, as reported in our previous work.…”

“…The graphene nanosheets were prepared using am odified Staudenmaier method, as reported in our previous work. [44,45] To decorate Ni nanoparticles onto Fe/CNTs, nickel(II) acetylacetonate (10 mg;S igma-Aldrich;9 9.9 %) and Fe/CNTs( 40 mg) were loaded into a5 00 mL stainless steel autoclave. Methanol (50 mL; TEDIA;99.9 %) was added as solvent miscible with SCCO 2 .Dimethyl amine borane (2 mg;T CI;9 5%)w as used as reducing agent.…”

Synthesis and characterization of graphene hollow spheres for application in supercapacitors

“…[26][27][28][29][30][31] We attribute the outstanding capacitive behaviour of graphene hollow spheres to their unique spherical structure (the graphene hollow spheres can maintain their structure aer being processed to fabricate supercapacitor electrodes (ESI, Fig. S3 †)).…”

Synthesis of nano-Cu/graphene oxide composites by supercritical CO2-assisted deposition as a novel material for reducing friction and wear

“…The readily accessible supercritical conditions, together with its abundance, low cost, non-flammability, and non-toxicity, have made supercritical carbon dioxide (scCO 2 ) promising for manufacturing various nanosize materials [21][22][23][24][25]. A few investigations showed that the nanoparticles possessed smaller size, narrower size distribution and more homogeneous distribution in the composites synthesized with assistance of scCO 2 , compared with the ones prepared without the assistance of scCO 2 [26][27][28][29]. The composites decorated with nanoparticles with the assistance of scCO 2 exhibit much better properties in applications.…”