With the rapid development of the Internet of Things, the development of highly sensitive and flexible chemical resistance sensitive gas sensors is of great research significance for real-time monitoring and safety warning of toxic and harmful gases.

For traditional silicon-based gas sensors, the problem of energy barrier mismatch between metal interdigital electrodes with high work function and semiconductor sensitive materials limits the effective charge transfer and sensing performance improvement. In this work, a fully flexible paper-based sensor integrating Ti3C2TxMXene non-metallic electrode (ME) and Ti3C2Tx/WS2 gas sensing materials was designed, which effectively solved the problem of energy barrier mismatch through the innovative design of homogeneous conductive electrode and sensitive materials.

Ti3C2Tx/WS2 nanosheet sensitive materials have the advantages of high conductivity, fast charge transfer and abundant active sites, and form ohmic contact and Schottky heterojunction in a single sensing channel with MXene homogeneous conductive electrode, and their heterojunction regulation effect, work function matching design and metal-induced gap state (MIGS) inhibition effect can effectively improve gas sensing performance.

The experimental results show that the gas sensing response value (15.2%) of 1 ppm NO2 of flexible paper-based ME+Ti3C2Tx/WS2 is 3.2 times that of the traditional golden interdigital electrode Au+Ti3C2Tx/WS2 sensing response value (4.8%), the minimum theoretical detection limit is 11.0 ppb, and it has excellent humidity stability. This work provides a new idea for the design of fully flexible gas sensors based on MXene homogeneous conductive electrode and gas sensing material integration.

Research highlights

1. Laser engraving-assisted imprinting technology is used to prepare flexible paper-based Ti3C2TxMXene low-power function non-metallic material electrodes, which reduces the energy difference between the traditional high-power function metal electrode and the semiconductor electron affinity, inhibits the formation of metal-induced gap states, and effectively increases the carrier migration rate at the gold-half interface.

2. A fully flexible gas sensor based on flexible paper-based homogeneous Ti3C2TxMXene electrode (ME) integrated Ti3C2Tx/WS2 gas sensitive material was constructed, which realized high sensitivity and high selectivity sensing of NO2 gas at room temperature, and its gas sensing performance was better than that of traditional golden interdigital electrode (AuE) integrated sensor.

3. The Ti3C2Tx/WS2 heterojunction regulation effect promotes the charge carrier transport efficiency at the interface, and synergistically enhances the adsorption performance and sensing response value of NO2. Adjusting the Schottky barrier height (SBH) and inhibiting the formation of metal-induced gap states can effectively avoid the Fermi level pinning effect, and realize the free transfer of charge carriers.