Role of Capping Agent in Palladium Nanoparticle Based Hydrogen Sensor (original) (raw)
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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.
Journal of Physics D: Applied Physics, 2011
This study reports a promising, cost-effective nanoscale hydrogen sensor fabricated using the dielectrophoresis (DEP) process. Palladium nanoparticles (NPs) of diameter in the range 2-4 nm were assembled in a 20 nm gap between electrodes under optimized DEP parameters of frequency, voltage and assembling time of 1 M Hz, 1.5 V and 90 s, respectively. The fabricated nanoscale device was powered by applying a dc voltage of 10 mV across nanogap electrodes and temporal change in resistance at an operating temperature of 160 • C was recorded in the presence of 3000 ppm of hydrogen gas. A rise and recovery times of 100 s and 300 s, respectively, in the temporal hydrogen gas response characteristic were observed which could be attributed to the hydride formation due to the strong affinity of assembled palladium NPs towards hydrogen. The nanoscale device was sensitive enough to respond to hydrogen presence even at 30 • C. Preliminary results show the potential of DEP in fabricating cost-effective nanoscale hydrogen sensor.
Polystyrene Palladium Nanocomposite for Hydrogen Sensing
Molecular Crystals and Liquid Crystals, 2005
In this paper, we report on the structure and hydrogen gas sensing properties of polystyrene palladium nanowire composites. Granular palladium nanowires (with 250 nm diameter) have been electrodeposited on Highly Oriented Pyrolytic Graphite (HOPG). In order to measure the electrical response of the sensor the nanowires were transferred to an insulating polystyrene surface. Polystyrene thin films with the thickness of about 150 nm were formed on a glass microslide by a dip-coating technique from a chloroform solution. Silver microelectrode pads were patterned on the surface of the nanocomposite by shadow masking technique. All stages of sensor device fabrication and its mechanism were monitored with application of atomic force microscopy technique (contact, non-contact, and force modulation modes).
Palladium-Functionalized Nanostructured Platforms for Enhanced Hydrogen Sensing
Nanomaterials and Nanotechnology, 2016
This paper reports on miniaturized hydrogen sensing platforms, exploring several means of fabricating nanostructured films and evaluating their sensing characteristics. Palladium-sputtered nanoporous organosilicate matrices are fabricated using the polymeric system [polymethylsilsesquioxane (PMSSQ); polypropylene glycol (PPG); propylene glycol methyl ether acetate (PGMEA)] followed by volatilization of the liquid phase, i.e., PGMEA and PPG at their boiling points. In order to provide greater adsorption/desorption sites for the test gas, ultra-dense ZnO nano-brushes with very high aspect ratios are successfully fabricated in the porous template. Thereafter, functionalization of ZnO is performed by sputter coating thin Pd films onto the ZnO surface. Intensive characterization for these nanostructures is performed using FESEM, EDAX, FTIR, TEM and AFM techniques. Comparison of all fabricated sensing platforms for hydrogen gas-dependent responses based on temperature, as well as test gas concentrations at various ppm levels, is performed. Palladium coating of ZnO nano-brushes renders this film highly selective to hydrogen and also improves its sensitivity by a factor of ~66% relative to the uncoated film. Sensitivity to hydrogen is found to be ~70% and a selectivity test is performed with CO 2 and CH 4, with sensitivities of 5% and 7%, respectively. Pd-functionalized ZnO nano-brushes display enhanced hydrogen response behaviour.
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.
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.
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.
ACS Applied Nano Materials, 2020
Surfactants and stabilizers are always present on the surfaces of colloidal nanocrystals due to their critical function in promoting selective facet growth and since they are essential to prevent aggregate formation in solution. After synthesis, however, the presence of these molecules on the surface of a nanocrystal is problematic because they potentially significantly alter the nature of the interaction with the environment, which is critical for sensor or catalysis applications. Here, we quantitatively scrutinize this effect experimentally for the four most common stabilizers in Pd nanoparticle synthesis: cetyltrimethylammonium bromide (CTAB), tetraoctylammonium bromide (TOAB), cetyltrimethylammonium chloride (CTAC), and poly(vinylpyrrolidone) (PVP). We use the surface-catalyzed hydrogen sorption and hydride formation reaction in Pd as a model system, due to its high relevance for hydrogen sensors. Specifically, we map in detail the (de)hydrogenation kinetics of arrays of nanofabricated Pd nanodisks in the presence of the surfactants and benchmark it with an uncoated Pd reference. As the key results, we find that the cationic surfactants significantly decelerate the (de)hydrogenation surface reaction, with the amplitude of deceleration mediated by the interplay between the halide-ion−Pd surface interaction strength and surfactant surface density. In contrast, a polymeric PVP coating is found to significantly accelerate hydrogen sorption. For the Pd-based hydrogen sensor application, our findings thus provide important insights for the appropriate choice of a surfactant to minimize the negative impact on hydrogen sorption kinetics and thus hydrogen detection response/recovery times. In a wider perspective, our results dramatically show how nanoparticles can attain different properties depending on what types of surfactants and stabilizers are present on their surface and how critical the quantitative understanding of their impact is for a specific application.
Palladium–polyelectrolyte hybrid nanoparticles for hydrogen sensor in fuel cells
Journal of Power Sources, 2009
We prepared palladium-polyelectrolyte hybrid nanoparticles by using a metallization of polyelectrolyte. In this study, we selected polyacrylic acid (PAA) as a polyelectrolyte and reduced the palladium ions on the PAA by using ascorbic acids in order to form a unique spherically shaped mosslike hybrid nanoparticle. Palladium (Pd) can absorb hydrogen to become PdH x , and the storage of hydrogen increases the electrical resistance and volume of Pd materials. The use of this material is attracting growing interest as a reliable, cheap, ultracompact, and safe hydrogen sensor for use in fuel cells. We showed the utilization of the Pd-PAA hybrid nanoparticles as a highly sensitive hydrogen sensor that exhibited a switch response depending on volume expansion in a cyclic atmosphere exchange.