Temperature dependent dual hydrogen sensor response of Pd nanoparticle decorated Al doped ZnO surfaces

Abstract

Sputter deposited Al doped ZnO (AZO) thin films exhibit a dual hydrogen sensing response in the temperature range 40 °C–150 °C after surface modifications with palladium nanoparticles. The unmodified AZO films showed no response in hydrogen in the temperature range 40 °C–150 °C. The operational temperature windows on the low and high temperature sides have been estimated by isolating the semiconductor-to-metal transition temperature zone of the sensor device. The gas response pattern was modeled by considering various adsorption isotherms, which revealed the dominance of heterogeneous adsorption characteristics. The Arrhenius adsorption barrier showed dual variation with change in hydrogen gas concentration on either side of the semiconductor-to-metal transition. A detailed analysis of the hydrogen gas response pattern by considering the changes in nano palladium due to hydrogen adsorption, and semiconductor-to-metal transition of nanocrystalline Al doped ZnO layer due to temperature, along with material characterization studies by glancing incidence X-ray diffraction, atomic force microscopy, and transmission electron microscopy, are presented.

Recent Advances in Palladium Nanoparticles-Based Hydrogen Sensors for Leak Detection

“…In these systems, Pd NPs can be found deposited directly on silicon or silica substrates [1,6,7,8,33]; they can also be deposited on other oxide materials (ZnO, WO 3 , etc.) [49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65]; in some works they functionalize carbon materials (graphene, CNTs, etc) [9,39,46,66,67,68,69,70,71] or are even alloyed to other metals [55]. These various types of sensors are investigated here.…”

“…Several teams have also investigated hydrogen sensors with a configuration of Pd NPs on various metal oxide (MO x ) structures [54,59,60,72]. Examples of devices working with Pd NPs-decorated ZnO [55,58,60], WO 3 [51,52,53,61,62,64], TiO 2 [56,57], NiO [54] and SnO 2 [49,65], among other MOx structures, are provided in the literature. Typically, while Pd NPs act as a catalyst in adsorption and dissociation of gas molecules, metal oxide structures ensure the electron conductive path.…”

“…First, when Pd NPs are directly deposited on Si or SiO 2 substrate, the metallic particles act as the sensing materials ensuring a conductive electron path by closing the gaps between particles due to volume expansion upon H 2 exposure [1,6,33]. Second, when Pd NPs are combined with carbon materials or metal oxide structures, the last mentioned ensure the electron conductive path and the role of the metallic particles is to act as a catalyst in adsorption and dissociation of gas molecules [9,39,46,49,54,56,58,59,60,65,66,67,68,70,72].…”

“… (a ) TEM image of Pd nanoparticles (~9.5 nm) used to decorate Al-doped ZnO surfaces for H 2 detection. Reprinted with permission from [58]. Copyright 2015 Journal of Applied Physics.…”

Linker-free chemical preparation of palladium nanoparticles on aluminum-doped zinc oxide electrodes for electrochemical water oxidation

“…The Al-doped ZnO (AZO) and Ga-doped ZnO (GZO) have extensively received much attention [29,30] and are examined for their use in optoelectronic devices [31]. Due to its semiconductor (n-type) properties having a direct bandgap, AZO is often used as the transparent electrical contact for solar cells and light-emitting diodes [30,32,33]. However, Al is cheap compared to other elements in the group [18].…”