Manipulation of palladium nanoparticles in a 20 nm gap between electrodes for hydrogen sensor application (original) (raw)
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Role of Capping Agent in Palladium Nanoparticle Based Hydrogen Sensor
Journal of Cluster Science, 2018
Palladium (Pd) nanoparticles (NPs) were synthesized via polyol route by varying concentration of capping agent, polyvinylepyrollidone (PVP). High resolution TEM study showed that the palladium nanoparticles were nearly spherical shape in the size range 11-13 nm. Hydrogen response pattern of the devices fabricated with the synthesized Pd NPs were recorded and were found to vary with the concentration of PVP. Also, response magnitude increased with PVP concentration for a particular pattern. Smooth recovery was observed both with and without the flow of carrier gas. While the sensor performance was found to be best at room temperature, the device performance deteriorated with the increase in temperature. Excellent long-term stability was observed as the devices showed similar response after 30 days of testing. The reproducible hydrogen response of these devices was supported by X-ray diffraction studies done on samples before and after hydrogen sensor study. The variation in response with the concentration of PVP is corroborated with a suitable sensing mechanism.
Pd Nanoparticles and Thin Films for Room Temperature Hydrogen Sensor
Nanoscale Research Letters, 2009
We report the application of palladium nanoparticles and thin films for hydrogen sensor. Electrochemically grown palladium particles with spherical shapes deposited on Si substrate and sputter deposited Pd thin films were used to detect hydrogen at room temperature. Grain size dependence of H 2 sensing behavior has been discussed for both types of Pd films. The electrochemically grown Pd nanoparticles were observed to show better hydrogen sensing response than the sputtered palladium thin films. The demonstration of size dependent room temperature H 2 sensing paves the ways to fabricate the room temperature metallic and metal-metal oxide semiconductor sensor by tuning the size of metal catalyst in mixed systems. H 2 sensing by the Pd nanostructures is attributed to the chemical and electronic sensitization mechanisms.
Shape dependent hydrogen response in palladium nanoparticle based sensors
Materials Today: Proceedings, 2020
Palladium nanoparticles (Pd NPs) with well-defined shape and controllable size were synthesized by Polyol strategy and the shape effect on hydrogen sensing at room temperature (RT) and beyond RT was detected. The evolution of shape in Pd NPs was dependent on the amount of stabilizer [Polyvinylpyrrolidone (PVP)] used during synthesis. Further, the dominant morphological facet in a particular shape determined whether the material will be suitable for room temperature or high temperature applications. The particle shape and facet hierarchy were analyzed using High Resolution Transmission Electron Microscopy (HRTEM) images, and Selected Area Electron Diffraction (SAED) patterns respectively. The hydrogen sensor studies revealed good response characteristics and the response parameters varied with the change in shape/facet characteristics of Pd nanoparticles. Also the variation of the hydrogen response with the increase in operating temperature was different for different shapes.
Journal of Electronic Materials, 2020
The size attributes in palladium nanoparticle yield were found to influence the hydrogen sensor response in resistive devices, and the sensing mechanism was correlated with the variation of particle size from large to small in a particular synthesis product. The quantity of polyvinylpyrrolidone (PVP), the stabilizer used in this study, was varied during synthesis, and the resulting sizes were determined by high-resolution transmission electron microscopy (HRTEM). The size tuning by the capping agent PVP was also confirmed by UV-Vis spectroscopy via a detailed analysis of the experimental spectra, which revealed an interesting shift of the major absorption peaks with the increase in PVP. Glancing-angle x-ray diffraction (GAXRD) studies were undertaken to highlight the face-centred cubic crystallinity of the drop-cast nanofilms on thin glass substrates, as well as to evaluate the variation in crystallite cluster size by analyzing the major diffraction peaks. The size variation from HRTEM and GAXRD studies was found to match within the limits of experimental accuracy. The hydrogen sensor studies showed good room temperature response with typical size-dependent characteristics. The mechanistic control of the hydrogen activity over the mixed sized nano-films at room temperature (RT) and beyond RT is elaborately discussed.
ACS Sensors, 2020
Hydrogen gas is rapidly approaching a global breakthrough as a carbon-free energy vector. In such a hydrogen economy, safety sensors for hydrogen leak detection will be an indispensable element along the entire value chain, from the site of hydrogen production to the point of consumption, due to the high flammability of hydrogen−air mixtures. To stimulate and guide the development of such sensors, industrial and governmental stakeholders have defined sets of strict performance targets, which are yet to be entirely fulfilled. In this Perspective, we summarize recent efforts and discuss research strategies for the development of hydrogen sensors that aim at meeting the set performance goals. In the first part, we describe the state-of-the-art for fast and selective hydrogen sensors at the research level, and we identify nanostructured Pd transducer materials as the common denominator in the best performing solutions. As a consequence, in the second part, we introduce the fundamentals of the Pd−hydrogen interaction to lay the foundation for a detailed discussion of key strategies and Pd-based material design rules necessary for the development of next generation high-performance nanostructured Pd-based hydrogen sensors that are on par with even the most stringent and challenging performance targets.
ACS Nano, 2010
lthough it has been known for more than 100 years that the absorption of hydrogen by palladium hydride, PdH x , increases its electrical resistivity, 1 it was not until 1992 that Hughes and Schubert 2 demonstrated that palladium alloy resistors consisting of ultrathin palladiumϪnickel alloy films could be used as H 2 sensors. In that work, PdϪNi(8Ϫ20%) films with thicknesses in the 50 nm range produced response times of ϳ10 s at 4% H 2 and ϳ20 s at 1% H 2 while achieving a limit of detection (LOD H 2) below 0.1%. 2 The presence of nickel in the palladium sensing element suppresses the ␣to -phase transition that is responsible, in pure palladium films, for irreproducibility and hysteresis in the detection of hydrogen at concentrations above 1% H 2 (at 300 K). The PdϪNi thin film resistor achieves many design objectives for hydrogen safety sensors including a low manufacturing cost, high sensitivity and accuracy, good stability, and a simple, rugged design, but its response times (10Ϫ20 s) are too slow by approximately an order of magnitude, based upon recent Department of Energy mandated performance metrics. 3 Several innovative resistive sensor designs have improved upon the response time of the Hughes thin film sensor at the expense of additional device complexity. For example, Wang and co-workers 4 prepared hydrogen-sensitive resistors by decorating nanoporous alumina surfaces with palladium nanoparticles. The resulting devices produced a response at 1% H 2 of ϳ1 s and a LOD H 2 of 500 ppm. 4 Dimeo et al. 5 described a MEMS-based hydrogen sensor in which thin films of a rare earth were employed as resistors on a microfabricated silicon platform 6 that facilitated the heating of these films to 50Ϫ 80°C. This device produced response times of 0.5 s and a LOD H 2 of less than 200 ppm. 5 A distinct subcategory of resistive hydrogen sensors involves ultrathin palladium film resistors that operate at the percolation threshold for electrical conduction. These sensors transduce the presence of hydrogen as a resistance decrease (⌬R H 2 Ͻ 0), in contrast to the resistance increase (⌬R H 2 Ͼ 0) normally seen for palladium resistors. Decreased resistance within the film is induced by volumetric swelling of -phase PdH x by 10% as compared with the ␣-phase, 1 opening new electrical pathways for transport within the film. Kaltenpoth et al. 7 were the first to observe this mechanism in ultrathin palladium films prepared within microfabricated silicon channels, but the performance of these devices was
Temperature balanced hydrogen sensor system with coupled palladium nanowires
Sensors and Actuators A: Physical, 2015
A temperature compensated hydrogen sensor was designed and made capable of detecting H 2 within a broad range of 100-10.000 ppm while compensating instantaneously for large (±25 • C) temperature variations. Two related operational constraints have been simultaneously addressed: (1) Selective, and sensitive detection under large temperature changes, (2) Fast warning at low and increasing H 2 levels. Accurate measurements of hydrogen concentrations were enabled by matching relevant time-constants. This was achieved with a microchip having two temperature coupled palladium nanowires. One of the H 2 sensitive Pd nanowires was directly exposed to hydrogen, whilst the other nanowire was used as a temperature sensor and as a reference. A drop forging technique was used to passivate the second Pd wire against H 2 sensing. Temperature effects could be substantially reduced with a digital signal processing algorithm. Measurements were done in a test chamber, enabling the hydrogen concentration to be controlled over short and long periods. An early response for H 2 sensing is attainable in the order of 600 milliseconds and an accurate value for the absolute hydrogen concentration can be obtained within 15 s.
Nanocrystalline Palladium Thin Films for Hydrogen Sensor Application
Sensor Letters, 2009
We report the application of palladium nanoparticles and thin films for hydrogen sensor. Electrochemically grown palladium particles with spherical shapes deposited on Si substrate and sputter deposited Pd thin films were used to detect hydrogen at room temperature. Grain size dependence of H 2 sensing behavior has been discussed for both types of Pd films. The electrochemically grown Pd nanoparticles were observed to show better hydrogen sensing response than the sputtered palladium thin films. The demonstration of size dependent room temperature H 2 sensing paves the ways to fabricate the room temperature metallic and metal-metal oxide semiconductor sensor by tuning the size of metal catalyst in mixed systems. H 2 sensing by the Pd nanostructures is attributed to the chemical and electronic sensitization mechanisms.
Sensors and Actuators B: Chemical, 2010
In this study, the sensing behaviour of palladium nanoparticle layers and thin film samples has been investigated for hydrogen and deuterium at room temperature and pressures between 4 and 5 Torr. Deuterium has been synthesised using electrolysis of heavy water. Nanoparticle as well as thin film samples show higher sensitivity for deuterium gas, in comparison to hydrogen gas, at all the gas pressures investigated. Nanoparticle sample shows faster sensing response for deuterium in comparison to hydrogen. It is interesting to note that palladium thin films show different sensitivity towards deuterium and hydrogen in comparison to palladium nanoparticles. This may be attributed to the difference in diffusivities of the two gases (deuterium and hydrogen) in palladium thin films. The results of this study indicate that by using a hybrid gas sensor, employing comparison of electrical resistance change in palladium nanoparticles and thin film, it may be feasible to differentiate between hydrogen and deuterium. The proposed sensor is based on the higher palladium diffusivity of deuterium in comparison to hydrogen, when the two gases are below the respective solubility limits.