Interfacial Hybridization-Enabled Chemiresistive Detection of Battery Electrolyte Vapors under Humid Conditions Using Polyoxometalate-Derived Dendritic WO 3 /Au Sensors

Electrolyte leakage from lithium-ion batteries constitutes a critical safety challenge as volatile and highly flammable organic carbonates can rapidly trigger fire and catastrophic thermal runaway. Diethyl carbonate (DEC), a widely used electrolyte solvent, is particularly hazardous, yet its selective detection under humid and chemically complex conditions remains highly challenging. Herein, an unconventional synthesis strategy is reported that departs fundamentally from traditional metal-ion precursors, employing a polyoxometalate molecular cluster (H 4 SiW 12 O 40 · x H 2 O, SiW 12 ) as a structure-directing, molecular-level precursor to construct dendritic WO 3 nanofibers uniformly decorated with Au nanoparticles (Au-D-WO 3 ) for ultratrace DEC sensing. The POM-guided process directs the in situ formation of defect-rich, hierarchically porous WO 3 dendrites, while the concurrent reduction of HAuCl 4 generates ultrafine Au NPs anchored on WO 3, creating abundant oxygen vacancies and well-defined Au/WO 3 Schottky interfaces. Benefiting from synergistic structural hierarchy and interfacial electronic modulation, the sensor exhibits ultratrace sensitivity and high selectivity toward DEC, robust humidity tolerance, and long-term stability. Density functional theory calculations reveal a transition from electrostatic- to hybridization-dominated adsorption at the Au/WO 3 interface, accounting for the enhanced and humidity-resilient sensing performance.