Ambiently Rapid Response and High Selectivity to NO₂ Enabled by Pd-rGO Composite Film-Coated Surface Acoustic Wave Sensor

In this study, we investigated a surface acoustic wave (SAW) sensor based on noble metal palladium-modified reduced graphene oxide (Pd-rGO) for the detection of a low concentration of NO2 gas at room temperature. A spin-coating technique was used to deposit Pd-rGO films onto an ST-cut quartz substrate. The SEM and Brunauer-Emmett–Teller (BET) characterization results indicate that the Pd-rGO composite film possesses large specific surface areas and provides sufficient adsorption active sites for NO2 gas. The experimental results showed that the prepared Pd-rGO SAW sensor had an enhanced gas-sensing performance to the NO2 gas (1–50 ppm) with high sensitivity (146.9 Hz/ppm), lower limit of detection (LOD, ~1 ppm), and excellent long-term stability, which can be attributed to the dissociation catalytic ability of the noble metal Pd. Meanwhile, compared to interfering gases such as CO, C6H6, C2H5OH, HCl, and H2S, the SAW sensor with Pd-rGO film exhibited a good selectivity toward NO2. These results identified the potential value of the Pd-rGO composite in the field of gas sensing, and it holds great promise in the realm of environmental protection.