High-Performance H₂ Sensors Based on a Hydrogen Spillover-Triggered Reversible W⁶⁺/W⁵⁺ Transformation Strategy for...

Noble-metal catalysts have been widely used for high-performance semiconductor metal oxide hydrogen sensors due to their excellent adsorption and activation capacity for H₂ molecules. However, the subsequent redox reaction between activated hydrogen (H*) and oxygen remains challenging due to the limited chemisorbed oxygen species on the surface of the semiconductor metal oxide. Here, we develop PtPd bimetallic nanoparticle-decorated WO₃ nanosheets to overcome this bottleneck by coupling hydrogen spillover with reversible W⁶⁺/W⁵⁺ transformation. Gas-sensing measurements show that PtPd-WO₃ gives a response of 298% toward 10 ppm H₂ at 150 °C, which is 37.3 and 3.6 times higher than those of pristine WO₃ and Pd-WO₃, respectively. The response time is reduced to 4 s (15 s for WO₃). Mechanism analysis reveals that the bimetal PtPd not only facilitates H₂ dissociation but also triggers the "activation" of the WO₃ surface. Abundant H* species, bypassing the limitation of chemisorbed oxygen species, permeate into the WO₃ lattice to drive reversible W⁶⁺ to W⁵⁺ reduction. This bulk-involved lattice redox process drastically modulates the resistance of WO₃ and amplifies the sensing signals. In situ Raman spectroscopy, gasochromic experiments, and density functional theory calculations substantiate that the PtPd-induced reversible lattice redox process is key to accelerating interfacial reactions. Finally, the PtPd-WO₃ sensor was integrated into a wireless platform for unmanned aerial vehicle-based and distributed pipeline monitoring, enabling real-time hydrogen leak localization.