Influence of MXene Composition on Triboelectricity of MXene-Alginate Nanocomposites

MXenes are highly versatile and conductive 2D materials that can significantly enhance the triboelectric properties of polymer nanocomposites. Despite the growing interest in the tunable chemistry of MXenes for energy applications, the effect of their chemical composition on triboelectric power generation has yet to be thoroughly studied. Here, we investigate the impact of the chemical composition of MXenes, specifically the Ti₃CNT_<i>x</i> carbonitride vs the most studied carbide, Ti₃C₂T_<i>x</i>, on their interactions with sodium alginate biopolymer and, ultimately, the performance of a triboelectric nanogenerator (TENG) device. Our results show that adding 2 wt % of Ti₃CNT_<i>x</i> to alginate produces a synergistic effect that generates a higher triboelectric output than the Ti₃C₂T_<i>x</i> system. Spectroscopic analyses suggest that a higher oxygen and fluorine content on the surface of Ti₃CNT_<i>x</i> enhances hydrogen bonding with the alginate matrix, thereby increasing the surface charge density of the alginate oxygen atoms. This was further supported by Kelvin probe force microscopy, which revealed a more negative surface potential on Ti₃CNT_<i>x</i>-alginate, facilitating high charge transfer between the TENG electrodes. The optimized Ti₃CNT_<i>x</i>-alginate nanogenerator delivered an output of 670 V, 15 μA, and 0.28 W/m². Additionally, we demonstrate that plasma oxidation of the MXene surface further enhances triboelectric performance. Due to the diverse surface terminations of MXene, we show that Ti₃CNT_<i>x</i>-alginate can function as either tribopositive or tribonegative material, depending on the counter-contacting material. Our findings provide a deeper understanding of how MXene composition affects their interaction with biopolymers and resulting tunable triboelectrification behavior. This opens up new avenues for developing flexible and efficient MXene-based TENG devices.