Measurement of the quantum capacitance of graphene. Nat. Nanotechnol. 4, 505

Center for Bioelectronics and Biosensors, Biodesign Institute, Department of Electrical Engineering, Arizona State University, Tempe, AZ 85287, USA.
Nature Nanotechnology (Impact Factor: 34.05). 09/2009; 4(8):505-9. DOI: 10.1038/nnano.2009.177
Source: PubMed


Graphene has received widespread attention due to its unique electronic properties. Much of the research conducted so far has focused on electron mobility, which is determined by scattering from charged impurities and other inhomogeneities. However, another important quantity, the quantum capacitance, has been largely overlooked. Here, we report a direct measurement of the quantum capacitance of graphene as a function of gate potential using a three-electrode electrochemical configuration. The quantum capacitance has a non-zero minimum at the Dirac point and a linear increase on both sides of the minimum with relatively small slopes. Our findings -- which are not predicted by theory for ideal graphene -- suggest that charged impurities also influences the quantum capacitance. We also measured the capacitance in aqueous solutions at different ionic concentrations, and our results strongly indicate that the long-standing puzzle about the interfacial capacitance in carbon-based electrodes has a quantum origin.

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Available from: Nongjian Tao, Dec 31, 2014
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    • "e l s e v i e r . c o m / l o c a t e / c a r b o n density of graphene [22] [23], caused by the intrinsic limitation of the electrostatic surface charging mechanism [17] [24] [25], have limited the graphene capacitance applications. Therefore the composite materials based on the graphene and some metal oxides with high capacitance have gained significant importance [18] [21] [26]. "
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    ABSTRACT: A self-propagating high-temperature synthesis (SHS) method to synthesize few-layer graphene (FLG) from magnesium and different carbon sources is demonstrated. These carbon sources include CaCO3, 3MgCO3·Mg(OH)2·3H2O, glucose, and polyvinyl alcohol (PVA). FLG produced by SHS method has a 3D porous structure with a special nanocrystallinity, and a low amount of defects. This fast, energy saving and low cost method is competitive as a candidate for industrial production of graphene for a wide range of applications. It is found that CaCO3 are superior to others among these starting materials according to DSC properties. The dye-sensitized solar cell (DSC) with a FLG (produced from CaCO3) counter electrode (CE) achieves a power conversion efficiency higher than that obtained with a reference DSC using a Pt counter electrode. The charge transfer resistance of FLG DSC is 0.13 Ω cm2, which is more than thirty times lower than that of the DSC having a Pt counter electrode. SHS FLG has been demonstrated to be a promising alternative counter electrode in DSC.
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    • "Measurement of the quantum capacitance of graphene. Xia J. et al 2009 Quantum capacitance in graphene by scanning probe microscopy. Giannazzo F. et al 2009 Capacitance of graphene nanoribbons. "
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    ABSTRACT: In this chapter, semi-analytical models for the calculation of the quantum capacitance of both monolayer and bilayer graphene and its nanoribbons, are presented. Since electron-hole puddles are experimental facts in all graphene samples, they have been incorporated in our calculations. The temperature dependence of the quantum capacitance around the charge neutrality point is also investigated and the obtained results are in agreement with many features recently observed in quantum capacitance measurements on both monolayer and bilayer graphene devices. Furtheremore, the impact of finite-size and edge effects on the quantum capacitance of graphene nanoribbons is studied taking into account both the edge bond relaxation and third-nearest-neighbour interaction in the band structure of GNRs.
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    • "Graphene has excellent electrical conductivity and large theoretical specific surface area (SSA) of 2630 m 2 g À1 [16], both of which are highly desirable for developing high-performance electrochemical capacitor [5] [17] [18]. It has been demonstrated that the graphene is capable of delivering a specific capacitance as large as 550 F g À1 providing that its surface is fully utilized for charge storage [19]. However, this value has yet been achieved as graphene sheets tend to restack into irreversible agglomerates through strong p-stacking and hydrophobic interactions, leading to a significant loss of surface area and remarkable decrease of ion diffusion rate in the interior of electrode. "
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    ABSTRACT: We present a facile and efficient route to introduce in-plane nanopores on the graphene sheets by activation of graphene aerogel (GA) with phosphoric acid (H3PO4). Results from N2 adsorption and TEM images showed that H3PO4 activation created mesopores with pore size of 2–8 nm on the graphene sheets. With such nanopores on graphene sheets, the activated GA exhibits a specific capacitance of 204 F g−1, enhanced rate capability (69% capacitance retention from 0.2 to 30 A g−1), reduced equivalent series resistance (3.8 mΩ) and shortened time constant (0.73 s) when comparing with the hydrothermally-derived pristine GA and thermally annealed GA in the absent of H3PO4. The excellent capacitive properties demonstrate that introduction of nanopores on GA by H3PO4 activation not only provides large ion-accessible surface area for efficient charge storage, but also promotes the kinetics of electrolyte across the graphene two-dimensional planes.
    Full-text · Article · Oct 2015 · Carbon
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