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The authors apologize for some errors contained in the published article. The error occurred due to a mistake in the calculation of the theoretical specific surface area of graphene. The errors in the paper do not alter the main experimental findings reported in the paper. Corrections are listed below.
- 1.On page 1: the theoretical specific surface area of 2624 m2 g−1 (for a theoretical specific capacitance of 131 F g−1) and a gravimetric energy density of 164 Wh kg−1 with organic electrolytes. This energy density, in particular, is ~4% to a value of 3700 Wh kg−1 for gasoline engines.
- 2.On page 4: Using the theoretical specific surface area of graphene mentioned in section 1 (2624 m2 g−1), we can estimate how many layers of graphene are stacked inside the powder RGO sample. The average number of stacked layers (n) in the RGO powder can be calculated as n = 2624/540 = 4.9 (for expanded RGO) or n = 2624/45 = 58 (for non-expanded RGO). Therefore, a few graphene layers are stacked for the RGO powder sample with a significantly large surface area.
- 3.The figure S1 in the supplementary information should be replaced with the following figure and text.
Figure S1. Calculations of the theoretical parameters (specific surface area, specific capacitance, and energy density) for graphene and graphene-containing supercapacitors. Using the atomic weight of carbon and lattice constants of graphene, the specific area of the graphene was calculated to be 2624 m2 g−1. To obtain a theoretical specific capacitance value for graphene, the magnitude of the specific area was multiplied by the capacitance per area value. Although a metallic surface can exhibit values as high as 21 µF cm−2, it decreased to 5 µF cm−2 for graphene because of the quantum capacitance effect [1]. The theoretical specific capacitance for graphene obtained by the calculations is 131 F g−1, while the theoretical energy densities for graphene-adopted supercapacitors are 18.2 Wh kg−1 for aqueous electrolytes and 164 Wh kg−1 for organic electrolytes. The observed specific capacitance values in the main text (121–222 F g−1) that exceed the theoretical value indicate a doping effect (which increases the quantum capacitance) is occurred on the RGOs due to the oxygen containing functional groups.
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