Pd-WO3 chemiresistive sensor with reinforced self-assembly for hydrogen detection at room temperature

Semiconducting metal oxides and metal catalysts have been widely used for gas sensors with high precision and reliability. In this study, we report a Pd-WO3 based chemiresistive sensor that can detect hydrogen at the ppm level at room temperature with a remarkably high response and selectivity. The colloidal solutions with Pd and WO3 nanoparticles were spray-deposited with controlled charge states of the droplets. The self-assembly of Pd nanoparticles (positive surface charge) and WO(3 )nanoparticles (negative surface charge) was reinforced with the positively charged droplets, producing Pd-WO3 nanoparticles with 1.68 times higher surface coverage of Pd on WO3 and a higher uniformity compared to those produced with neutral droplets. The optimized Pd-WO3 sensor fabricated by the positively charged droplets exhibits a 160 times higher response and 3.51 times faster response for 100 ppm of hydrogen than sensors fabricated by the neutral droplets, detecting hydrogen concentrations as low as 1 ppm with excellent cyclic stability, selectivity, and reproducibility.