Hydrogen Sensitivity and Mechanism of Pd/V2O5 Thin Films

Abstract-Pd/V₂O₅ double layer films were deposited on glass substrates by magnetron sputtering. The hydrogen sensing properties of the films were analyzed using a UV-visible spectrophotometer. The surface morphology of the films was observed under a scanning electron microscope. Hydrogen sensing mechanism of the Pd/V₂O₅ films was researched on the basis of Raman spectra. The obtained Pd/V₂O₅ films are sensitive to hydrogen. A change of about 25% in relative transmittance at 560 nm can be observed when a Pd (30 nm)/V₂O₅ (280 nm) film was exposed to 4% hydrogen. No obvious defect can be observed after the films were exposed to hydrogen. For the magnetron sputtered Pd/V₂O₅ double layer films, the Pd layer mainly acts as a catalyst. The hydrogen molecules adsorbed on the Pd layer are dissociated into hydrogen atoms. When the hydrogen atoms diffuse into the inner V₂O₅ layers, V₂O₅ reacts with hydrogen, resulting the transformation of some V⁵⁺ into V⁴⁺ and the formation of vanadium bronze and as well as the change in the transmittance of the films.