Nitrogen and sulfur Co-doped 2D titanium carbides for enhanced electrochemical performance

Two-dimensional (2D) transition metal carbides (MXenes) have been recently attracted as promising electrode materials for energy storage applications. Herein, we report a high-capacity supercapacitor material based on nitrogen and sulfur co-doped titanium carbides (NS-Ti₃C₂), which is prepared by a simple thiourea-assisted carbonization of large-scale Ti₃C₂ nanosheets. Importantly, results indicate that the 2D Ti₃C₂ treated with thiourea-assisted carbonization results in change in its microstructure, specific surface area, and mesopores. And, it also has a crucial effect on co-doping content and position of N and S, which can improve the accessibility to active sites. The carbonization treated NS-Ti₃C₂ nanosheets exhibit a high specific capacitance of 175 F g^-1 at 2 mV s-1 in 1 M Li2SO4 electrolyte solution, and a prominent cycling stability (90.1% of the initial capacitance after 5000 cycles). The significant improvement in electrochemical performance of the NS-Ti₃C₂ can be attributed to larger surface areas and more mesopores, actually, the doping of N and S can enhance the intercalation of ion electrolyte, provide more abundant electrical charge, and thus contribute to the pseudocapacitance. Hence, this new type of nitrogen and sulfur co-doped Ti₃C₂ could be a promising electrode material for high-performance supercapacitors.