Construction of 3D N-doped Ti₃C₂/TiO₂ hollow sphere structure with superior electrochemical performance for supercapacitor

Herein, the 3D N-doped Ti3C2/TiO2 sphere structure is constructed via an innovative three-step method including the preparation of 3D Ti3C2 microspheres with PMMA as templates, the situ-growth of TiO2 nanoparticles on Ti3C2 and the subsequent annealing treatment in NH3. N element is doped in composite after annealing in NH3 to improve the transfer rate of ions and electrons, and N-doped Ti3C2/TiO2 hollow composite provides an abundant active surface for the sufficient contact between electrodes and electrolytes to enhance charge transport and electrolyte diffusion. Benefiting the unique structure feature and the synergistic effects of active materials, the N-doped Ti3C2/TiO2 electrode exhibits a high specific capacitance of 572 F g(-1) at a current density of 1 A g(-1) and a superior cyclic stability of 99.6% of its initial value for 9500 cycles at 10 A g(-1). Based on this, a symmetric supercapacitor (SSC) based on N-doped Ti3C2/TiO2 electrode is further assembled. The SSC shows a competitive capacitance of 157 F g(-1) at 1 A g(-1). More importantly, the comparable energy density of 17.7 Wh kg(-1) is achieved at the power density of 450 W kg(-1). This work will give promising guidance for designing and fabricating the durable electrodes with excellent electrochemical behavior for practical application in future.