Influence of PdHx formation ability on hydrogen sensing properties of palladium-carbonaceous films

• Nanocomposite Pd-C films from PVD process were modified by annealing and by CVD method.
• Palladium hydride PdHx is formed in nanocomposite Pd-C films under the influence of hydrogen.
• Pd-C films after annealing process react faster to H2 in comparison to CVD films.
• Response of the annealed PVD films is reversible and durable under gas containing 1 vol% of hydrogen.

In this paper we present new nanocomposite materials ability to use in hydrogen sensing applications. Nanocomposite films were obtained by several techniques such as PVD, PVD/CVD (physical vapor deposition/chemical vapor deposition) methods as well as by annealing of films prepared by PVD process. The films are composed of Pd nanograins embedded in the carbonaceous matrix. These Pd nanograins are responsible for palladium hydride PdHx formation. Creation of PdHx in these films was observed during in situ GIXD (graizing incidence X-ray diffraction) measurements. The hydrogen sensing characteristics by dc electrical measurements were also shown. We discuss how the structure of Pd-C films, palladium nanograins and the carbon matrix affect the sensing properties in terms of response time, sensitivity and reversibility.