Nitrogen Doped Intercalation TiO₂/TiN/Ti₃C₂T_x Nanocomposite Electrodes with Enhanced Pseudocapacitance

Layered two-dimensional titanium carbide (Ti₃C₂T_x), as an outstanding MXene member, has captured increasing attention in supercapacitor applications due to its excellent chemical and physical properties. However, the low gravimetric capacitance of Ti₃C₂T_x restricts its rapid development in such applications. Herein, this work demonstrates an effective and facile hydrothermal approach to synthesize nitrogen doped intercalation TiO₂/TiN/Ti₃C₂T_x with greatly improved gravimetric capacitance and excellent cycling stability. The hexamethylenetetramine (C₆H₁₂N₄) in hydrothermal environment acted as the nitrogen source and intercalants, while the Ti₃C₂T_x itself was the titanium source of TiO₂ and TiN. We tested the optimized nitrogen doped intercalation TiO₂/TiN/Ti₃C₂T_x electrodes in H₂SO₄, Li₂SO₄, Na₂SO₄, LiOH and KOH electrolytes, respectively. The electrode in H₂SO₄ electrolyte delivered the best electrochemical performance with high gravimetric capacitance of 361 F g^-1 at 1 A g^-1 and excellent cycling stability of 85.8% after 10,000 charge/discharge cycles. A systematic study of material characterization combined with the electrochemical performances disclosed that TiO₂/TiN nanoparticles, the introduction of nitrogen and the NH₄⁺ intercalation efficaciously increased the specific surface areas, which is beneficial for facilitating electrolyte ions transportation. Given the excellent performance, nitrogen doped intercalation TiO₂/TiN/Ti₃C₂T_x bodes well as a promising pseudocapacitor electrode for energy storage applications.