Spatially confined surface-terminated MXene nanosheets as a multifunctional platform for triboelectric sensing and logic gates

Abstract

Spatially confined microcapacitive networks formed at polar-group-terminated 2D nanosheet/polymer interfaces play a pivotal role in charge trapping and retention. This study utilizes delaminated MXene (Ti₃C₂T_X) sheets embedded in polydimethylsiloxane (PDMS) and electrospun ethyl cellulose (EC) nanofibers as frictional layers in a contact-separation vertical triboelectric nanogenerator (TENG) configuration. The 'PDMS-EC' TENG, without MXene fillers, exhibited an open-circuit voltage (V_OC) of 155 V and a short-circuit current (I_SC) of 425 nA. Incorporating MXene nanosheets terminated with polar functional groups into PDMS enhances the dielectric permittivity, thereby forming a microcapacitive network and localized charge trapping sites. The optimized 'PDMS/MXene-EC' TENG containing 1 wt% MXene yields a significant enhancement in V_OC of ∼295 V, I_SC of ∼1.5 µA, and power density of ∼3 W m⁻². COMSOL Multiphysics simulations validated the experimental results, exhibiting a simulated V_OC of 267 V. Kelvin probe force microscopy (KPFM) analysis revealed an increased triboelectric surface charge density from 38.6 to 52.1 µC m⁻² for PDMS/MXene, accompanied by a decreased surface potential from 18.28 to 6.32 mV. First-principles DFT calculations reveal charge transfer between PDMS and MXene sheets, evidenced by electrostatic potential redistribution and density of states analysis. Near-ideal square waveforms (duty cycles ≈ 49.7%) with controllable pulse width and amplitude are realized using rectifiers and filter circuits. The generated output waveforms facilitate the processing of a binary-to-decimal decoder system and Boolean logic operations. MXene-fused TENGs, with their multifaceted ability to charge capacitors, power LEDs, and generate stable square waveforms for digital signal processing, showcase their potential as scalable energy harvesters and self-powered sensors.