Core morphology effect of Pd-Au_NR@ZnO core-shell nanoparticles on hydrogen gas sensing properties

In this study, the Pd@Au core-shell nanorod (CS-NR) with Au shell thickness of about 3 nm is first prepared and then the Zn(OH)₂ nanoparticle (NP) outer shell is covered over the Pd@Au CS-NR core by the hydrothermal method. It is noteworthy that the Pd@Au_NR@Zn(OH)₂ double CS-NPs are transformed into Pd-Au_NR@ZnO CS-NPs with nanorod-shaped Pd-Au alloy cores after calcination at 500ºC. The Pd-Au_NR@ZnO sensor exhibits higher hydrogen sensitivity than Au_NR@ZnO and pure ZnO sensors. Indeed, the Pd-Au_NR@ZnO sensor shows a higher response (105) for 100 ppm of hydrogen at 250ºC. Additionally, in comparison to Au_NR@ZnO and pure ZnO sensors, the Pd-Au_NR@ZnO sensor presents quicker response and recovery times. Moreover, it is found that the Pd-Au_NR@ZnO sensor can detect a hydrogen concentration down to 1 ppm at low temperature (150ºC). Furthermore, this sensor demonstrates a much greater selectivity for hydrogen gas than other target gases such as acetaldehyde, ethanol, methane, and carbon monoxide. These enhancements could be ascribed to the core morphology, electronic sensitization, and hydrogen absorption effect of the Pd-Au alloy nanorod-shaped core.