W18O49 sensitized with Pd nanoparticles for ultrasensitive ppb-level formaldehyde detection

The rapid detection of ppb-level formaldehyde is desirable but challenging for both air quality monitoring and health. Herein, we adopt the ultrasonic-solvothermal method to co-assemble W and Pd precursors to developing a direct and controllable flower-like W18O49 synthesis method, in which evenly dispersed Pd NPs are tightly fixed on the surface of the nanostructure for efficient formaldehyde detection. The sensitization of Pd NPs increases the oxygen vacancies and provides plenty of accessible sites for gas molecules. Meanwhile, the synergistic effect of Pd NPs and flower-like W18O49 interface promotes electron transfer. Thus, the enhanced gas sensing performance of the Pd-sensitized W18O49 could be attributed to chemical and electronic sensitization. The Pd-sensitized W18O49 sensor exhibits extremely low actual detection concentration (50 ppb), ultrasensitive (2.96/50 ppb), ultrafast response (1 sec), excellent reversibility, and good selectivity. DFT theoretical calculations systematically validate the gas sensing mechanism of Pd-sensitized W18O49 for formaldehyde. This work provides new insights into the design strategy of Pd-sensitized W18O49 nanomaterials for high-performance quantitative detection of formaldehyde gas sensors.