Thin palladium nanograins film for efficient and selective hydrogen sensor

The development of reliable hydrogen sensors is pivotal for safety in hydrogen technologies. This paper presents the palladium material's ability for hydrogen sensing applications. The thin palladium nanograins films (Pd film) composed of nanograins show highly selective properties towards hydrogen. The films were obtained by palladium acetate evaporation via the Physical Vapor Deposition method. Scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) were employed for studying the topography and morphology of films. The FTIR spectra demonstrated a total decomposition of Pd acetate during the deposition process while the TEM results received at high resolution mode confirmed that fine Pd nanograins with face-centred cubic (fcc) crystal structure were created. The sensing properties have been studied for different hydrogen concentrations from 50 ppm to 20,000 ppm in ambient conditions. The Pd nanograin films exhibited high sensitivity to hydrogen at concentrations as low as 0.005% and excellent selectivity against methane and ammonia. During the measurements, a decrease in the electrical resistance of films was observed. The formation of PdH_x was responsible for this phenomenon and it was proved by the in-situ XRD studies. These findings suggest that Pd nanograin films are promising for hydrogen sensor technology.