Real-time monitoring of harmful gases is of great significance to identify the environmental hazards to people's lives. However, this application scenario requiring low-power consumption, superior sensitivity, portability, and self-driven operation of gas sensors remains a challenge. Herein, an electrospun triboelectric nanogenerator (TENG) is synthesized using highly electronegative and conducting MXene nanofibers (NFs) paired with biodegradable cellulose acetate NFs (CA-NFs) as triboelectric layers, which supports a sufficient power density (∼1361 mW/m 2 @2 MΩ) and shows a self-powered ability to operate the chemiresistive gas sensor fabricated in this work. Further, by using cellulose nanofibers (C-NFs) as a substrate, a new kind of MXene/TiO 2 /C-NFs heterojunction-based sensory component is developed for detection of NH 3 . This sensor exhibits excellent reproducibility, high selectivity, and sensitivity toward NH 3 (1−100 ppm) along with a fast response/recovery time (76 s/62 s) at room temperature. Finally, a monitoring system comprising a TENG-powered sensor, an equivalent circuit, and an LED visualizer has been assembled and successfully demonstrated as a fully self-powered device for NH 3 leakage detection. Thus, this work pushes forward the intelligent gas sensing network self-driven by human motion energy, dispensing the external battery dependence for environment monitoring to reduce the possible health effects.

The architecture of an ammonia (NH 3 ) monitoring system that serves as a versatile tool for real-time breath sampling and environmental gas sensing is proposed herein. By means of first-principles density functional theory (DFT) simulations, an edge-site-enriched MXene/MoS 2 nanosheet heterostructure is systematically investigated and used both as a sensing material and an active layer of a hybrid tribo-/piezonanogenerator (H-TPNG). This allows combining the potential of gas sensing and energy harvesting into a single device, with benefits of self-powered monitoring of NH 3 . The high selectivity, reversibility, and sensitivity (47%@10 ppm) of the prepared sensor to target NH 3 gas are revealed, resulting from the increased adsorption sites and improved charge transfer at the edge sites observed from DFT studies. On the other hand, the mechanical tapping and bending motions of the H-TPNG effectively stimulate the instantaneous triboelectric and piezoelectric power densities of 1604.44 and 15.62 mW/cm 2 , respectively. Additionally, the nanofibrous morphology of the H-TPNG introduced by the electrospinning technique provides great flexibility and conformability to the device for large-area integration of body parts. Finally, a self-powered NH 3 monitoring system is assembled which demonstrates the autonomous operation of a sensor for breath analysis and environmental monitoring and could pave the way for the advancement of wearable monitors for healthcare applications.

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The low surface charge density and consequent unsatisfactory energy conversion efficiency of nanogenerators hinder their capacious utility toward the emerging field of wearable electronics. The strategy of introducing dielectric fillers into a polymer matrix attempts to improve dielectric constant and, thereby, to enhance surface charge density but can hardly yield sufficient energy conversion efficiency. Herein, we report a high performance flexible and compressible triboelectric nanogenerator (FC-TENG) based on a lead-free dielectric material, potassium sodium niobate (KNN), embedded with Ti3C2Tx MXene fillers, blended into poly-vinyl alcohol (PVA) using an electrospinning technique. The role of MXene in dielectric functionalization is to promote the interfacial polarization effect by forming micro-capacitor structures or percolation systems and, thereby, to endow high charge-inducing and charge-trapping capabilities. As a result, the prepared 4 vol. % MXene loaded KNN/PVA nanofibers achieve a higher dielectric constant/dielectric loss factor, which leads to enhanced energy conversion efficiency of FC-TENGs with a maximum power density of ∼2780 mW/cm2. In addition, the selected device was employed into shoe-insoles to demonstrate its ability of capturing biomechanical energy, which reveals its potential to be utilized as a wearable power-source for next generation devices.