Intercalation and surface modification of two-dimensional transition metal carbonitride Ti3CNTx for ultrafast supercapacitors

Abstract

MXenes are promising supercapacitor electrodes due to their two-dimensional structure and electrochemically active surface. As a member of MXenes, Ti₃CNT_x is a transition metal carbonitride with a similar structure to Ti₃C₂T_x, and it is considered to have excellent electrochemical performance. However, the electrochemical performance of Ti₃CNT_x is usually limited by nanosheet agglomeration and surface terminations the same as that of Ti₃C₂T_x. In this work, we demonstrated that intercalating K⁺ and removing surface terminations (–OH, –F) significantly improved the gravimetric capacitance of Ti₃CNT_x up to 464 F g⁻¹. Furthermore, the introduction of Ag nanowires between Ti₃CNT_x layers can further enhance the charge transport through Ti₃CNT_x films, and it revealed a very high gravimetric capacitance of 245 F g⁻¹ even at 2000 mV s⁻¹. The as-assembled all-solid-state symmetric supercapacitors showed an energy density of 6.9 mW h g⁻¹, indicating their promising potential for flexible electronic devices. These results proved that intercalation and surface modification can significantly enhance the electrochemical performance of Ti₃CNT_x films, promoting the development of Ti₃CNT_x-based electrodes, which have broad application prospects in flexible supercapacitors, wearable electric devices, and other fields.