Synthesis of ultra-high specific surface area aerogels with nitrogen-enriched Ti₃C₂T_x nanosheets as high-performance supercapacitor electrodes

Chemical doping of MXenes with heteroatoms is expected to be a promising strategy for enhancing their electrochemical performance. Nevertheless, the synergistic effects of chemical doping and 3D structure construction have rarely been investigated in depth. Aiming to avoid MXene nanosheet restacking and further enhance the electrochemical performance, herein, we reported a simple strategy combining nitrogen doping with a 3D structure construction on MXenes via a one-step hydrothermal method. The location and types of nitrogen doping can be adjusted by hydrothermal conditions. The obtained nitrogen-doped Ti₃C₂T_x aerogel had an ultra-high specific surface area of 200.8 m² g⁻¹ with high porosity. The open reticular walls can expose more nitrogen-enriched Ti₃C₂T_x edges to the electrolyte. Nitrogen dopants at the edges of Ti₃C₂T_x nanosheets produced more number of active sites and provided higher pseudocapacitance, and the presence of N-C₄ increased the electron mobility of Ti₃C₂T_x, which reduced charge transfer resistance evidently. As a result, the nitrogen-doped Ti₃C₂T_x aerogel showed an excellent specific capacitance (531 F g⁻¹ in H₂SO₄ electrolyte) with good cyclic stability (remaining 96% after 5000 cycles).