Comparison of ruthenium composites with thermally reduced graphene and activated carbon for supercapacitor applications

Ruthenium composites are synthesized by using a sol–gel method with thermally reduced graphene and activation carbon. The specific capacitance of the ruthenium composite with graphene is much higher (440 F g−1) than that of the composite with activated carbon (246 F g−1). The difference is due to the different hydrous and anhydrous ruthenium content of the composites. The activated carbon has micro pores (8.7 Å) with a three-dimensional structure, while the graphene has meso pores (68.9 Å) in a two dimensional structure, resulting that the hydrous ruthenium is likely to be intercalated into graphene rather than the activated carbon. The ruthenium composite with graphene, therefore, has a similar amount of hydrous and anhydrous ruthenium, offering optimized proton and electron paths for electrolyte ions with respect to supercapacitor performance. The composite with activated carbon, however, has more anhydrous ruthenium than the hydrous ruthenium, thereby limiting the proton path. As a result, the ruthenium composite with thermally reduced graphene could provide effective and positive electrodes for supercapacitor applications.