Pd2 + –doped WO3 nanowires for enhanced triethylamine sensing: low-concentration detection enabled at reduced operating temperatures

Noble metals are often used as sensitizers for gas sensing materials, accompanied by multiple sensitization mechanisms. Unlike conventional noble metal surface loading, this work reports a material system in which Pd 2+ are doped into the WO 3 lattice and redundant Pd 2+ generate surface–anchored PdO x clusters, coexisting in two forms. XRD analysis demonstrated that the larger Pd 2+ (0.86 Å) ions replacing W 6+ (0.60 Å) ions in WO 3 lattice resulted in an obvious left shift of the diffraction peaks and also the peak fusion due to lattice disorder. XPS test confirmed that Pd existed only in two states, Pd 2+ and Pd 4+ , and there was no stable metallic Pd 0 phase in the composite material. SEM observations revealed a continuous nanowire morphology across all the Pd ratios, and PdO particles were identified to attach to the nanowire surface via TEM. The synergistic effect of lattice doping (Pd 2+ ) and surface loading (PdO x ) greatly enhanced the sensing performance of WO 3 . The 2.5 at% Pd/WO 3 nanowires (NWs) sensor achieved the maximum response toward 20 ppm triethylamine (TEA) at 160 °C. Compared with that of pure WO 3 NWs (220 °C), its response to 20 ppm TEA increased significantly from 14.5 to 1100 (approximately 75.9 times greater). Moreover, the recovery time of the 2.5 at% Pd/WO 3 NWs sensor was much shorter (30 s) than that of the pure WO 3 NWs (265 s), and its theoretical limit of detection (LOD) was ultralow, with an LOD of 5 ppb. More importantly, the 2.5 at% Pd/WO 3 NWs sensor possessed excellent selectivity for TEA. Finally, the mechanism by which Pd modification enhanced WO 3 gas-sensing performance was systematically elucidated. This study establishes a comprehensive theoretical–experimental foundation for engineering TEA sensors with simultaneously improved sensitivity and selectivity. • Pd 2+ –doped WO 3 nanowires via electrospinning&calcination yield—ultra-sensitive TEA gas sensors. • 2.5 at% Pd/WO 3 nanowires sensor reaches an ultrahigh response of 1100–20 ppm TEA gas at 160 °C. • 2.5 at% Pd/WO 3 nanowires sensor achieves ultralow TEA gas detection limit of 5 ppb. • Pd modification comprises synergistic effect of catalytic sensitization, electronic sensitization, and defect engineering. • Dual-mode operation: max sensitivity (160 °C) or rapid kinetics (200 °C).