An oxidation-resistant and elastic mesoporous carbon, graphene mesosponge (GMS), is prepared. GMS has a sponge-like mesoporous framework (mean pore size is 5.8 nm) consisting mostly of single-layer graphene walls, which realizes a high electric conductivity and a large surface area (1940 m 2 g −1 ). Moreover, the graphene-based framework includes only a very small amount of edge sites, thereby achieving much higher stability against oxidation than conventional porous carbons such as carbon blacks and activated carbons. Thus, GMS can simultaneously possess seemingly incompatible properties; the advantages of graphitized carbon materials (high conductivity and high oxidation resistance) and porous carbons (large surface area). These unique features allow GMS to exhibit a suffi cient capacitance (125 F g −1 ), wide potential window (4 V), and good rate capability as an electrode material for electric double-layer capacitors utilizing an organic electrolyte. Hence, GMS achieves a high energy density of 59.3 Wh kg −1 (material mass base), which is more than twice that of commercial materials. Moreover, the continuous graphene framework makes GMS mechanically tough and extremely elastic, and its mean pore size (5.8 nm) can be reversibly compressed down to 0.7 nm by simply applying mechanical force. The sponge-like elastic property enables an advanced force-induced adsorption control.

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In the present study, we introduced a simple method for the fabrication of Au͑111͒-like polycrystalline Au electrodes via the formation of a submonolayer ͓i.e., sub-self-assembled monolayer ͑sub-SAM͒/Au͔ of a thiol compound ͓e.g., cysteine ͑CYST͒, mercaptoacetic acid, or cystamine͔. The oxygen reduction reaction ͑ORR͒ in alkaline medium (O 2 -saturated 0.5 M KOH͒ performed at these sub-SAM/Au electrodes proceeds via a two-electron quasi-reversible pathway irrespective of the charge of the terminal group of the thiol ͓with anodic-to-cathodic peak separation (⌬E p ) of about 60 mV͔. This behavior is similar to that observed at the Au͑111͒ single-crystalline electrode in the same medium. The presence of iodide ions in the alkaline medium leads to a significant negative shift of the reduction peak while the anodic peak is completely ceased. This indicates the blocking of the Au͑111͒ domain of the sub-SAM/Au by the iodide ions, leading to the complete inhibition of the anodic oxidation of the hydrogen peroxide formed during the cathodic scan. At the CYST sub-SAM/Au electrodes, the O 2 reduction is completely hindered in O 2 -saturated 0.1 M KI, while the quasi-reversible behavior of the sub-SAM/Au electrode toward the ORR is restored after ten successive potential cycles between ϩ200 and Ϫ500 mV at a scan rate of 50 mV s Ϫ1 in O 2 -saturated 0.5 M KOH. This indicates the high stability of the submonolayer of CYST at the Au electrode and that the I Ϫ ions ͓which possess a strong adsorption tendency toward Au͔ cannot replace the CYST molecules.

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