Fabrication of Pd-decorated tungsten oxide nanoflakes for hydrogen sensors via facile anodizing oxidation method

Abstract

Accurate and reliable hydrogen sensing is crucial for safety and efficiency in industries like energy, transportation, and environmental monitoring. This study presents the synthesis and characterization of Pd-decorated WO3 nanoflakes with palladium (Pd) nanoparticles from anodizing derived WO3.2(H2O) nanoflakes for gas sensing applications. We investigate the crystal structure and phase composition of the synthesized nanoflakes using X-ray diffraction (XRD) and Raman spectroscopy, which confirm the presence of well-crystallized monoclinic WO3.2(H2O) phase without any impurities or secondary phases. Field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) reveal the unique morphology of the nanoflakes with irregular edges and varying sizes, as well as the successful decoration of Pd nanoparticles on the nanoflake surface. X-ray photoelectron spectroscopy (XPS) analysis indicates partial oxidation of tungsten species upon interaction with PdCl2 solution. We evaluate the gas sensing characteristics of the decorated nanoflakes towards hydrogen gas, demonstrating an enhanced response at elevated temperatures (>300 °C). The introduction of Pd nanoparticles improves the gas sensing response up to 6000 due to increased hydrogen dissociation and catalytic activity, as well as enhanced electrical conductivity. The response and recovery times of the sensors are rapid, indicating efficient response-recovery behavior. These findings suggest the potential of anodizing method for fabrication of WO3.2(H2O) nanoflakes as promising candidates for gas sensing applications.