Investigation of the hydrogen gas sensing properties of nanoporous Pd alloy films based on AAO templates

In this study, the hydrogen sensing properties of nanoporous Pd–Ag and Pd–Cu alloy films based on anodic aluminum oxide (AAO) templates were investigated at various temperatures (25–100 °C) and hydrogen with concentrations in the range between 250 and 5000 ppm in high purity nitrogen to determine the temperature–sensitivity relationship. A hexagonally shaped AAO template of approximately 50 nm in diameter and 10 μm in length was fabricated as a substrate for supporting a nanoporous Pd alloy film with an approximate thickness of 80 nm. The morphologies of the AAO template and the Pd alloy films were studied by scanning electron microscopy (SEM). The hydrogen sensing properties of the nanoporous Pd–Ag and Pd–Cu alloy films were measured using a transient resistance method. The sensor responses of the nanoporous Pd–Ag and Pd–Cu films on the AAO template were better than the traditional Pd–Ag and Pd–Cu thin film sensors; the sensitivities of the sensors were approximately 1.6% and 1.2%, respectively, for 1000 ppm H2, and the detection limit was 250 ppm at room temperature. The highest sensitivity was measured at room temperature for all alloy nanoporous sensors, and the sensitivity of the Pd–Ag nanoporous alloy was higher than that of the Pd–Cu nanoporous alloy.

Research highlights
► Pd–Cu and Pd–Ag alloys have been evaporated on an AAO template which was approximately 50 nm in diameter and 10 μm in length to obtain nanoporous films.
► The hydrogen sensing properties of the alloy films have been investigated in the concentrations range of 250–5000 ppm at various temperatures.
► The highest sensitivity was measured at room temperature for all alloy nanoporous sensors.
► The sensitivity of the Pd–Ag nanoporous alloy was higher than that of the Pd–Cu nanoporous alloy.