A low temperature hydrogen sensor based on palladium nanoparticles

Palladium nanoparticles were synthesized by employing Polyol solution chemistry technique. In this method ethylene glycol was used to reduce sodium tetrachloropalladate at 100 °C in presence of polyvinylpyrrolidone (PVP) to yield ∼10 nm sized particles, which was confirmed by transmission electron microscopy (TEM) studies. Thin films of the synthesized nanoparticles on glass substrates were characterized by glancing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM) to check crystallinity and surface morphology, respectively. Both TEM and GIXRD results support the faceted geometry of nanoparticles. Resistive sensor devices were fabricated with palladium films on glass substrates by laying fine silver paste lines in the form of interdigitated fingers. The hydrogen sensor studies at different temperatures (35–75 °C) with gas concentrations (0.1–1%) in nitrogen revealed a dual response trend. The device resistance increased slightly and then decreased sharply upon exposure to hydrogen in nitrogen. Optimum response was obtained at 50 °C, with response time (t90) of 3 s in 1000 ppm hydrogen in nitrogen. Similar studies in air showed only increase in resistance. The data reveal the decrease in response time with the decrease in hydrogen concentration, which is an optimistic result from application viewpoint. Detailed analysis of the results along with the selectivity studies has been presented.