Room temperature ultrasensitive ppb-level H2S SAW gas sensor based on hybrid CuO@V2C MXene van der Waals heterostructure

Abstract

The rise of Internet of Things (IoT) technology has driven a growing demand for the smart gas sensors capable of detecting trace-level hazardous gases with high accuracy, and rapid response at room temperature (RT) is crucial for environment and human health protection. In this study, we report the fabrication of an electrostatic self-assembly-assisted CuO@V₂C MXene-based hybrid van der Waals heterostructure (vdW-HS) coated on a surface acoustic wave (SAW) sensor for ultrasensitive and low-ppb level H₂S detection at RT. The hybrid SAW sensor revealed excellent selectivity, notable sensitivity (~ 39.71 kHz), and faster response/recovery (54/76 s) times to H₂S gas (20 ppm), with low detection limit (~ 27.2 ppb), outperforming its pristine counterparts. Significantly, the hybrid SAW sensor demonstrated superior reversibility, satisfactory long-term stability, and enhanced sensitivity under various elevated temperatures (RT-200 °C) and relative humidity (0 to 80%) conditions. These substantial improvements in H₂S sensing performances of the hybrid SAW sensor can be accredited to the increased surface area, abundant surface terminal groups, defect states, oxygen vacancies, and the Schottky barrier modulation at CuO@V₂C MXene vdW-HS, which collectively enhance the charge transfer and higher H₂S gas adsorption. Furthermore, the density functional theory (DFT) calculations showed that the hybrid composite sensor has a higher adsorption energy for H₂S than pristine sensors, facilitating enhanced H₂S adsorption. The H₂S sensing mechanism is comprehensively elucidated using energy band theory. This study presents a robust framework for cost-effective, high-performance room-temperature smart gas sensors based on hybrid vdW-HS, enabling applications in environmental protection, healthcare and industrial monitoring.

Graphical Abstract