Nanocomposite NiO:Pd hydrogen sensors with sub-ppm detection limit and   low operating temperature
  We present results on the fabrication of chemiresistive nanocomposite NiO:Pd hydrogen sensors, which are able to detect hydrogen concentrations as low as 300 ppb in air, operating at temperatures in the 115-145 C range. Thin NiO films were deposited by radio frequency magnetron sputtering on silicon and quartz substrates and their structural and morphological properties were characterized. Pd nanoparticles were added on the NiO surface via pulsed laser deposition and the films were tested as hydrogen sensors before and after Pd deposition. The presence of Pd nanoparticles improved the sensor performance, leading to the detection of hydrogen concentrations at sub-ppm levels. Moreover, the response time of the sensors decreased by a factor between two and four. 
M. Kandyla, C. Chatzimanolis-Moustakas, M. Guziewicz, and M. Kompitsas
cond-mat.mtrl-sci