High-performance aqueous asymmetric electrochemical capacitors based on graphene oxide/cobalt(ii)-tetrapyrazinoporphyrazine hybrids

Abstract

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 Na2SO4 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.