Fabrication of palladium-gold alloy nanostructures, characterization and investigation of their gas sensing properties

In Pd-based resistive hydrogen sensors, hysteresis, due to delays in Pd hydrogen absorption-desorption processes and α-β phase transformations, leads to different sensor resistance values when hydrogen concentration is increased and decreased. A proposed method to overcome this is the use of Pd alloys. In this study, Pd-Au alloy thin films were produced on different substrates using magnetron sputtering techniques. Furthermore, to produce a Pd-Au alloy with a different nanostructure, nanoporous structures were obtained by coating the films onto anodic aluminum oxide (AAO) nanosubstrates. AAO nanosubstrates were produced by anodization. Subsequently, the structural analysis of the prepared nanostructured Pd-Au alloys and AAO nanosubstrates was investigated using SEM, EDX, and XRD techniques. In the next stage, the electrical properties and gas sensor properties of the prepared nanostructured Pd-Au alloys were investigated. The diameter of the AAO nanotube pores, formed by anodization at 60 volts with a 0.4 M phosphoric acid solution for 60 minutes, is approximately 75 nm. The diameter decreases in AAO nanotubes coated with Pd-Au alloy. The response of the formed Pd-Au thin-film sensor to 1% H2 gas improved significantly as the temperature increased. When different Pd-Au film thicknesses were examined, it was observed that the sensor sensitivity decreased as the film thickness increased. At 120°C and a film thickness of 10 nm, the highest sensor response and the fastest response time were obtained for the Pd-Au nanoporous sensor.