Synergistically Boosting the Surface Reaction Dynamics by K ⁺ Interstitial Doping in Pd/WO ₃ Nanosheets for Robust Hydrogen Sensing

The development of highly sensitive and reliable hydrogen detection technology is a critical prerequisite for the safe and large-scale application of green hydrogen energy. Pd-based metal oxide semiconductor sensors exhibit decent sensing performance; however, their development for hydrogen detection is hindered by competitive adsorption of hydrogen and oxygen on the surface and sluggish reaction kinetics due to limited active interfaces. Here, a series of Pd nanoparticle-decorated, K⁺ interstitial doping WO₃ nanosheets (Pd_NP-K/WO₃-<i>x</i>) were synthesized. The optimized Pd_NP-K/WO₃-15 sample exhibited exceptional H₂ sensing performance, including a high response (<i>R</i>_a/<i>R</i>_g = 1235.94 to 50 ppm H₂) at a low temperature of 130 °C, with fast response/recovery. This enhancement stems from synergistic effects where K⁺ interstitial doping increases electron density and oxygen vacancies in WO₃, improving charge transfer and strengthening the W-O-Pd interface. The resulting electron-rich environment also shifts the <i>d</i>-band center of Pd, enhancing hydrogen desorption and spillover, while reducing competitive oxygen adsorption to free up more Pd active sites. The material also showed promising room-temperature sensing, indicating strong application potential and providing a theoretical basis for designing high-performance alkali metal ion-doped metal oxide materials.