Hydrogen gas sensing properties of PdO thin films with nano-sized cracks

Abstract

We report on a novel method for the fabrication of highly sensitive hydrogen gas sensors based on palladium oxide thin films and have investigated their hydrogen sensing properties and nanostructures. To our knowledge, this is the first report on the use of palladium oxide and reduced palladium thin films as hydrogen sensors. The palladium oxide thin films were deposited on thermally oxidized Si substrates using a reactive direct current (DC) magnetron sputtering system. Considerable changes in the resistance of the palladium oxide thin films were observed when they were initially exposed to hydrogen gas, as a result of the reduction process. After the initial exposure to hydrogen gas of PdO(30%), its sensitivity increased up to approximately 4.5 x 10(3)%. The morphology of the PdO surface was analyzed using a scanning electron microscope (SEM), in order to investigate the interactions between palladium oxide and hydrogen. The SEM images showed a large number of nano-sized cracks on the surface of the palladium oxide during the reduction process, which acted to increase the effective surface-to-volume ratio. The response behaviors of the reduced Pd films to hydrogen gas were reversible and had an enhanced sensing property when compared with those of the pure Pd films. In addition, their sensitivities and response times were improved due to the nano-sized cracks on the surfaces. The results demonstrate that palladium oxide and reduced palladium thin films can be applied for use in highly sensitive hydrogen sensors.

Nanostructured PdO Thin Film from Langmuir–Blodgett Precursor for Room-Temperature H2 Gas Sensing

“…Only recently, H 2 gas sensing of pure PdO thin film with nano-sized cracks and nanoflakes has been reported. 10,11 However, no recovery has been observed for this sensor at room temperature. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 4 In general, thin films of PdO are prepared either by reactive sputtering 12 or by oxidation of Pd metal.…”

Gas sensing behavior of palladium oxide for carbon monoxide at low working temperature

“…In comparison to other metals, palladium shows the highest catalytic activity for hydrocarbons and carbon monoxide oxidation [26]. A number of research groups suggested PdO is the active phase in the process of catalytic combustion [7,12,27,28]. In the region of low temperature, PdO has stable chemical properties and high thermal stability [12,26].…”

Influence of Electrochemical Hydrogenation on the Circular Photocurrent in the Ag/Pd Nanocomposite

“…The current density in the electrolytic cell was 0.7 mA cm −2 . The Ag/Pd film composition was changed as a result of chemical reaction PdO + H → Pd + H 2 O . Furthermore, during the hydrogenation the chemical reaction PbO + H → Pb + H 2 O, in which Pb reduces from amorphous PbO (from the structural component of the initial paste), can occur.…”