Influence of MXene Composition on Triboelectricity of MXene-Alginate Nanocomposites

Abstract

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_x carbonitride vs the most studied carbide, Ti₃C₂T_x, 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_x to alginate produces a synergistic effect that generates a higher triboelectric output than the Ti₃C₂T_x system. Spectroscopic analyses suggest that a higher oxygen and fluorine content on the surface of Ti₃CNT_x 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_x-alginate, facilitating high charge transfer between the TENG electrodes. The optimized Ti₃CNT_x-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_x-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.

Keywords: MXene; TENG; Ti3CNTx; alginate; hydrogen bonding; nanocomposite; triboelectricity.

Figure 1

Schematic overview of the study. (a) Preparation of MXene-alginate nanocomposite; delaminated Ti₃C₂/Ti₃CN flakes mixed with sodium alginate solution, followed by drop-casting onto carbon fiber paper; includes SEM images of Ti₃C₂ and Ti₃CN flakes and the top surface of the resultant nanocomposite coating. (b) Illustration of a TENG device setup with an inset showing a cross-section SEM image of MXene-alginate coated carbon fiber paper, a proposed mechanism illustrating the interactions between MXene and alginate, and the resulting triboelectric voltage curves.

Figure 2

Characterization of MXenes and MXene-alginate nanocomposites. TEM images of (a) Ti₃C₂ and (b) Ti₃CN, with insets showing their respective SAED patterns (scale bars refer to 5 1/nm). XPS core level spectra, including curve fittings for Ti 2p and O 1s of (c,d) Ti₃C₂ and (e,f) Ti₃CN, respectively. SEM images of (g) the cross-section and (h) the surface of the Ti₃CN-Alg coating on carbon fiber paper. EDS elemental maps obtained from (i) Ti₃CN-Alg coating displaying (j) carbon, (k) oxygen, and (l) nitrogen distribution.

Figure 3

Influence of the MXene composition on the hydrogen bond interactions and triboelectric behavior. (a) Illustration of the TENG working principle, (b) triboelectric output voltage curves of alginate, the MXenes, and the MXene-alginate composites, (c) FTIR spectra of the OH band region, (d) contact potential difference (CPD) distribution curves.

Figure 4

Influence of plasma oxidation on triboelectric performance. Triboelectric voltage and current output of Ti₃CN-alginate (a,b) and alginate (c,d) films subjected to varying durations of oxygen plasma treatment.

Figure 5

Triboelectric behavior with different counter dielectric layers. (a) Voltage curves of the nanocomposites contacted with FEP (i), PET (ii), and nylon (iii). (b) Enlarged voltage curves of Ti₃CN-alginate with FEP and nylon. (c) Illustration of contact electrification of Ti₃CN-Alg with FEP and nylon, respectively, indicating the triboactive functional groups in each polymer.

Figure 6

Triboelectric power generation with respect to excitation conditions. (a) Voltage output of x% Ti₃CN-alginate (x = 0–4). (b) Voltage and (c) current output as a function of the contact frequency and (d) voltage vs. contact force of 2% Ti₃CN-alginate, respectively. (e) Power load and current curve, (f) capacitor charging curves, (g) powering of LEDs and a small device with 2%Ti₃CN-alginate, (h) cycling stability, and (i) SEM images of 2%Ti₃CN-alginate before and after the cycling test.