Prototype Alarm Integrating Pulse-Driven Nitrogen Dioxide Sensor Based on Holey Graphene Oxide/In₂O₃

NO₂ seriously threatens human health and the ecological environment. However, the fabrication of highly sensitive NO₂ sensors with rapid response/recovery rates, low detection limits, and ease of integration remains a challenge. Herein, benefiting from the fast carrier transfer and rich active sites, holey graphene oxide (HGO) was adopted to functionalize the In₂O₃ nanosheet to construct NO₂ gas sensors. Characterization and theoretical calculations established the merits of HGO decoration in the NO₂ sensing. The optimal sample, 0.5 wt % HGO/In₂O₃-sheet, exhibited superior sensing properties, resulting in a 1.37-fold improvement in response to 1 ppm of NO₂ compared to the GO/In₂O₃ counterpart. Gas-sensing kinetics analysis revealed its lower activation energy and higher kinetic rate constants. Importantly, pulsed-temperature modulation was employed to decouple the gas adsorption from surface activation processes, achieving an ultrahigh response of 2776 to 1 ppm of NO₂ for the 0.5 wt % HGO/In₂O₃-sheet sensor. Compared to the isothermal mode, this strategy enhanced the response value by 1.6 times, reduced the response/recovery time by 33%/70%, and enabled the detection of NO₂ concentrations as low as 1 ppb. Finally, an NO₂ monitoring alarm system based on the 0.5 wt % HGO/In₂O₃-sheet sensor with pulsed-temperature modulation was demonstrated for hazard warnings.