Carbon nitride mediated synthesis of titanium-based electrodes for high-performance asymmetric supercapacitors

Rational design of electrode materials with specific compositions and unique morphological and structural features to achieve supercapacitors (SCs) with high energy densities without compromising their inherent electrochemical merits remains a great challenge. Herein, a carbon nitride (C3N4) mediated “one-for-two” strategy was proposed to synthesize titanium nitride/carbon nanosheets (TiN/C) and titanium carbide/carbon nanosheets (TiC/C) with three-dimensional morphology and hierarchical structure, respectively. The derived TiN/C and TiC/C were used as cathode and anode materials, respectively, with excellent capacitor behavior in aqueous electrolyte. Specifically, asymmetric SCs constructed with the TiN/C cathode and the TiC/C anode delivered a large operation voltage of 0.3–1.8 V, a high specific capacitance of 103 F·g−1, and a remarkable energy density of 45.2 Wh·kg−1, outperforming most of the previously reported TiN- and TiC-based SCs. Ex situ XRD and TEM characterizations as well as DFT simulation indicated that the excellent performance could be attributed to reversible pseudocapacitive redox reaction and electro-adsorbed anions at the TiN/C cathode, and fast adsorption/desorption of cations at the TiC/C anode, as well as unique surface morphology and heterostructure. The strategy presented in this work also provides new design concepts for the synthesis of other transition metal nitrides (or carbides)/carbon composites for other advanced energy applications.