Ultraviolet Photothermal Radiation Customized Nitrogen Terminals of Ti₃C₂T MXene for High-Performance Supercapacitors

Two-dimensional MXenes have emerged as exceptional electrode materials for supercapacitors (SCs), making them highly attractive for energy storage and conversion applications. However, their electrochemical performance is strongly influenced by surface terminal groups and interlayer spacing. In this study, we introduce an ultraviolet(UV)-induced nitrogen-doping method that employs UV radiation to promote the thermal decomposition of ammonium oxalate while inducing nitrogen-doping. The resulting UV-induced nitrogen-doped Ti₃C₂T (I-Ti₃C₂T-N) exhibits a high N doping level of 1.46 at. % and an expanded lattice spacing of 1.43 nm. As a result, I-Ti₃C₂T-N demonstrates exceptional pseudocapacitance performance, achieving a remarkable specific capacitance of 466.28 F g^-1, significantly exceeding that of raw Ti₃C₂T (367.96 F g^-1). Furthermore, when integrated into a quasi-solid-state SC device, it delivers an impressive energy density of 12.58 Wh kg^-1 at a power density of 250.00 W kg^-1. The enhanced electrochemical performance of I-Ti₃C₂T-N is attributed to the effects of UV radiation, which introduces N terminal groups, eliminates detrimental -F and -OH terminals, and increases interlayer spacing. This study highlights a simple yet effective UV-induced nitrogen-doping method for modifying MXene materials, offering another way for optimizing their electrochemical properties in energy storage applications.