Article

Measurement of the quantum capacitance of graphene

Center for Bioelectronics and Biosensors, Biodesign Institute, Department of Electrical Engineering, Arizona State University, Tempe, AZ 85287, USA.
Nature Nanotechnology (Impact Factor: 33.27). 09/2009; 4(8):505-9. DOI: 10.1038/nnano.2009.177
Source: PubMed

ABSTRACT 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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    • "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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    Carbon 10/2015; 92. DOI:10.1016/j.carbon.2015.02.052 · 6.16 Impact Factor
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    • "In our previous study, we investigated the effect of polyethylene glycol (PEG) on the electromechanical properties of a CMC-based actuator created with BMIMBr ionic liquid (Ozdemir et al. 2015). Graphene, which is a stable 2D one-atom-layer material, shows excellent properties, i.e., good electrical conductivity and mechanical strength, a large surface area and superior performance (Huang et al. 2012; Lee et al. 2008; Novoselov et al. 2004; Xia et al. 2009). Feng et al. (2012) emphasized that graphene loading enhanced the electrical and mechanical properties . "
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    • "However, the performance of two-dimensional (2D) graphene sheets is severely limited by the poor accessibilities with electrolytes and the sheet aggregations during the processes of material syntheses and/or the electrode fabrications due to the strong van der Waals interactions between the neighboring sheets [12] [21], which lead to that the amount of effective surface electrostatic charge accumulation is low and the interlayer channels of the graphene for ionic/electronic transports are partially blocked. Thus, the capacitance values of the reported 2D graphene-based electrodes are usually in the range of 100– 200 F g À1 [22] [23] [24], which are far below the theoretical value of 550 F g À1 calculated for the graphenes with an ideal single layer distribution [5] [18]. "
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