Achieving Ultrahigh Energy Densities of Supercapacitors with Porous Titanium Carbide/Boron-Doped Diamond Composite Electrodes

The energy densities of most supercapacitors (SCs) are low, hindering their practical applications. To construct SCs with ultrahigh energy densities, a porous titanium carbide (TiC)/boron-doped diamond (BDD) composite electrode is synthesized on a titanium plate that is pretreated using a plasma electrolytic oxidation (PEO) technique. The porous and nanometer-thick TiO2 layer formed during PEO process prevents the formation of brittle titanium hydride and enhances the BDD growth during chemical vapor deposition processes. Meanwhile, the in situ conversion of TiO2 into TiC is achieved. Combination of this capacitor electrode with soluble redox electrolytes leads to the fabrication of high-performance SCs in both aqueous and organic solutions. In 0.05 m Fe(CN)(6)(3-/4-) + 1 m Na2SO4 aqueous solution, the capacitance is as high as 46.3 mF cm(-2) at a current density of 1 mA cm(-2); this capacitance remains 92% of its initial value even after 10 000 charge/discharge cycles; the energy density is up to 47.4 Wh kg(-1) at a power density of 2236 W kg(-1). The performance of constructed SCs is superior to most available SCs and some electrochemical energy storage devices like batteries. Such a porous capacitor electrode is thus promising for the construction of high-performance SCs for practical applications.