Graphene-family nanomaterials assembled with cobalt oxides and cobalt nanoparticles as hybrid supercapacitive electrodes
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Sara B. Carrizosa Department of Chemistry, Western Kentucky University, KY 42101, USA
Benjamin McDonald Department of Geology, Western Kentucky University, KY 42101, USA
Jacek Jasinski Department of Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Kentucky, KY 40292, USA
Nikolaos Dimakis Department of Physics, The University of Texas-Rio Grande Valley, TX 78539, USA (Received 30 July 2016; accepted 28 November 2016)
We report the development of hybrids consisting of supercapacitive graphene oxide (GO), reduced GO (rGO), electrochemically reduced GO (ErGO), multilayer graphene (MLG) decorated with pseudocapacitive nanostructured cobalt oxides (CoO, Co3O4) and nanoparticles (CoNP) via electrodeposition and hydrothermal synthesis facilitating chemically bridged (covalently and electrostatically anchored) interfaces with tunable properties. These hybrid samples showed heterogeneous transport behavior determining diffusion coefficient (4 108–6 106 m2/s) following CoO/MLG , Co3O4/MLG , Co3O4/rGOHT , CoO/ErGO, CoNP/MLG and delivering the maximum specific capacitance .550 F/g for Co3O4/ErGO and Co3O4/MLG. We found an ultrahigh sensitivity of 4.57 mA/(mM cm2) and excellent limit of glucose detection ,50 nM following Co3O4/rGOHT , CoO/ErGO , CoNP/MLG , Co3O4/MLG. These findings are due to open pore network and topologically multiplexed conductive pathways provided by graphene nanoscaffolds to ensure rapid charge transfer and ion conduction. Density functional theory determined density of states in the vicinity of Fermi level in-turn providing contribution toward electroactivity due to orbital re-hybridization.
I. INTRODUCTION
Intense research activities and development in alternative and sustainable energy sources are stimulated by increasing global demand of electrical energy for portable electronics and mobile technology. The electrochemical energy storage systems (supercapacitors and pseudocapacitors) represent efficient and environmentally benign technologies as compared to intermittent solar and wind energy sources. Electrochemical supercapacitors are playing a vital role due to high power density, fast power delivery and long cycle life. These characteristics are complementary to batteries for uninterruptible back-up power supplies, load-leveling, power brakes in hybrid
Contributing Editor: Gary L. Messing a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.484
automobiles and hybrid electronics.1,2 Important to mention, the charge storage mechanism in supercapacitors are classified into: (i) electrochemical double layer, where the electrostatic charge is accumulated through surface ion adsorption on electrodes surface and (ii) pseudocapacitors, where charge is transferred in redox materials without altering the structure and composition (non-faradaic) that is stark contrast to battery processes which are faradaic. While supercapacitors possess higher theoretical specific capacitances due to higher specific surface area and
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