High-performance aqueous asymmetric electrochemical capacitors based on graphene oxide/cobalt(ii)-tetrapyrazinoporphyrazine hybrids
Journal of Materials Chemistry A
Department of Chemistry, University of Pretoria, Pretoria 0002, South Africa; Energy Materials, Materials Science and Manufacturing, Council for Scientific and Industrial Research (CSIR), Pretoria 0001, South Africa; Department of Physics, University of Pretoria, Pretoria 0002, South Africa; Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan; Department of Chemistry and Biochemistry, University of California, Santa Cruz CA, United States; Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8520, Japan
A novel asymmetric electrochemical capacitor (AEC) with high energy and power densities has been developed using a graphene oxide/cobalt(ii) tetrapyrazinoporphyrazine composite (GO/CoTPyzPz) as the positive electrode and graphene oxide/carbon black (GO/CB) as the negative electrode in a neutral aqueous Na<inf>2</inf>SO<inf>4</inf> electrolyte. The excellent specific capacitance, energy and power densities (∼500 F g-1, 44 W h kg-1 and 31 kW kg-1) coupled with long cycle life, excellent short response time, and low equivalent series resistance clearly indicate that this new material has great potential for the development of low-cost and 'green' aqueous AECs that operate at high energy and power densities. Interestingly, the energy density of the GO/CoTPyzPz//GOCB based AEC falls within the range usually observed for nickel metal hydride (NiMH) batteries (30-100 W h kg-1), but more importantly, shows better power performance than NiMH batteries (0.25-1 kW kg-1) widely used in hybrid vehicles such as Toyota Prius and Honda Insight. © 2013 The Royal Society of Chemistry.
Capacitors; Electric resistance; Hybrid vehicles; Electrochemical capacitor; Equivalent series resistance; Negative electrode; Nickel metal hydride battery; Positive electrodes; Power performance; Short response time; Specific capacitance; Graphene