Hydrogen Gas Concentration Research Articles

Synthesis, Fabrication and Characterization of ZnO-Based Thin Films Prepared by Sol–Gel Process and H2 Gas Sensing Performance

In this paper, an attempt is made to deposit ZnO thin films using sol–gel process followed by dip-coating method on p-silicon (100) substrates for intended application as a hydrogen gas sensor owing to the low toxic nature and thermal stability of ZnO. The thin films are annealed under annealing temperatures of 350, 450 and 550 °C for 25 min. The crystalline quality of the fabricated thin films is then analyzed by field-emission scanning electron microscopy and transmission electron microscope. The gas sensing performance analysis of ZnO thin films is demonstrated at different annealing temperatures and hydrogen gas concentrations ranging from 100 to 3000 ppm. Results obtained show that the sensitivity is significantly improved as annealing temperature increases with maximum sensitivity being achieved at 550 °C annealing temperature and operating temperature of 150 °C. Hence, the modified ZnO thin films can be applicable as H2 gas sensing device showing to the improved performance in comparison with unmodified thin-film sensor.

Inhalation of hydrogen gas attenuates airway inflammation and oxidative stress in allergic asthmatic mice

BackgroundAsthma is a worldwide common chronic airway disease that cannot be cured and results in the huge burden in public health. Oxidative stress was considered an important mechanism in the pathogenesis of asthma. Hydrogen gas been demonstrated to function as a novel antioxidant and exert therapeutic antioxidant activity in a number of diseases and the function of this nontoxic gas in asthma was unclear. The purpose of the study aims to examine the effect of inhalation hydrogen gas on the pathophysiology of a mouse model of asthma.MethodsA murine model of ovalbumin (OVA)-induced allergic airway inflammation was used in this study. Briefly, Mice were sensitized to ovalbumin and received inhalation of 67% high concentration of hydrogen gas for 60 min once a day for 7 consecutive days after OVA or PBS challenge respectively. Lung function was assessed in the apparatus with 4 channels of biological signal system. Morphology and goblet cell hyperplasia were stained by H/E and Periodic acid-Schiff staining. Cytologic classification in the bronchial alveolar lavage fluid (BALF) was analyzed by Wright Giemsa staining. Serum, BALF and lung tissue were collected for biochemical assay. One-way analysis of variance (ANOVA) was used to determine statistical significance between groups. Multiple comparisons were made by Bonferroni’s Multiple Comparison Test by using GraphPad Prism 5 software.ResultsInhalation of hydrogen gas abrogated ovalbumin-induced the increase in lung resistance. Concomitantly, the asthmatic mice showed severe inflammatory infiltration and goblet cell hyperplasia which were reversed by hydrogen gas inhalation. Hydrogen gas inhalation reduced significantly the number of total cells, eosinophils and lymphocytes in BALF. Increased level of IL-4, IL-13, TNF-α and CXCL15 in the BALF and IL-4 in the serum were decreased significantly after inhalation. Hydrogen gas inhalation markedly upregulated the activity of decreased superoxide dismutase and significantly attenuated the increased level of malondialdehyde and myeloperoxidase.ConclusionsHydrogen gas inhalation improves lung function and protects established airway inflammation in the allergic asthmatic mice model which may be associated with the inhibition of oxidative stress process. This study provides a potential alternative therapeutic opportunity for the clinical management of asthma.

燃料極支持型SOFCにおける燃料極内の水素濃度計測

Mass transfers in porous electrodes of fuel cells affect the performance of the fuel cells. The aim of this study is to verify effectiveness of a measurement method of a hydrogen gas concentration in a fuel electrode of a solid oxide fuel cell (SOFC) to clarify the mass transfer mechanism. This technique was applied to a SOFC which was composed of 8 mol % Y2O3-ZrO2 (YSZ) electrolyte and Ni-YSZ fuel electrode. A sensor which was made of a platinum wire coated with zirconia and alumina was inserted into the fuel electrode to measure the oxygen partial pressure. The hydrogen gas concentration was determined from the oxygen partial pressure which was obtained from an electromotive force of the sensor using Nernst's equation. The hydrogen gas concentration decreased with increasing the current density up to 0.45 A/cm2 and also with increasing the operating temperature (1173 K to 1273 K) at the same current density. The measured values of the hydrogen gas concentration were proportional to the values calculated by three dimensional numerical simulation. These results indicated the measurement method had a potential for the measurement of hydrogen gas concentrations in fuel electrodes. Furthermore, the effective diffusivity of hydrogen gas in the fuel electrode could be obtained from the hydrogen gas concentration.

Stability and storage properties of hydrocarbons obtained by pilot scale pyrolysis of real waste HDPE-PVC in tubular reactor

In this work the mixtures of real waste high-density polyethylene, low-density polyethylene, polypropylene and polyvinyl-chloride (PVC) were pyrolyzed in a pilot scale horizontal tubular reactor using different synthetic zeolite catalysts. Raw material was fed into the reactor through an electrically heated screw feeder, and then decomposed in the reactor. Products were separated into gases, pyrolysis oil and heavy fraction by atmospheric distillation. The yields of gases and pyrolysis oils can be significantly increased by using catalysts, but the catalyst properties were key parameter. For instance, Ni/ZSM-5 catalyst can increase the hydrogen content in gases and isomerize the carbon framework of hydrocarbons. Pyrolysis oils contained C5-C35 hydrocarbons; however their properties were modified by catalysts. An accelerated aging test was performed to follow the long term behavior of products. Pyrolysis oils were treated at 80 °C for 7 d, and then the stability of pyrolysis oils was assessed by evaluating the density, solid deposition and acid number. Unsaturated hydrocarbons in pyrolysis oils can agglomerate during the aging. On the other hand the catalysts can improve their properties. Pyrolysis oils obtained by thermo-catalytic pyrolysis resulted with less corrosion than in case of without catalysts.

Hydrogen gas concentration measurement in small area using raman lidar measurement technnology

When change of hydrogen(H2) gas concentration in a certain point is measured, non-contact measurement technology with high temporal and spatial resolution is necessary. In this study, H2 concentration in the small area of <1cm2 under the gas flow was measured by using a Raman lidar. Raman scattering light at the measurement point of 750mm ahead was detected by the Raman lidar. As a result, it was proved that the H2 concentration of more than 100ppm could be successfully measured.

Ultra-High Sensitivity to Low Hydrogen Gas Concentration With Pd-Decorated IGZO Film

To enhance the performance of semiconducting metal oxides, as hydrogen (H2) sensor, we introduced a high carrier concentration ( ${N}_{d}$ ) metal oxide, indium-gallium–zinc oxide (IGZO), combined with palladium (Pd) catalysis. This allowed the detection of low concentrations of H2 at room temperature. The base current level was linearly increased with the Pd thickness. As a result, a high sensor sensitivity of $6.1 \times 10^{6}$ % at 5% H2 concentration was obtained using a 1-nm-thick Pd-decorated IGZO film. Comparative studies with a zinc oxide (ZnO) counterpart showed that the ${N}_{d}$ of IGZO ( $8 \times 10^{18}$ cm $^{-3}$ ) is significantly higher than that of ZnO ( $2 \times 10^{16}$ cm $^{-3}$ ), indicating a closer location for the Fermi level of IGZO to the conduction band. Therefore, a relatively small amount of electron-donating H2 was required to overcome the energy barrier in IGZO. Consequently, the 1-nm-thick Pd-decorated IGZO sensor responded to a gas level as low as 0.01% (100 ppm) and demonstrated a 70-fold higher sensitivity compared with ZnO sensor at all H2 concentrations.

Raman lidar for hydrogen gas concentration monitoring and future radioactive waste management.

A multi-channel Raman lidar has been developed, allowing for the first time simultaneous and high-resolution profiling of hydrogen gas and water vapor. The lidar measures vibrational Raman scattering in the UV (355 nm) domain. It works in a high-bandwidth photon counting regime using fast SiPM detectors and takes into account the spectral overlap between hydrogen and water vapor Raman spectra. Measurement of concentration profiles of H2 and H2O are demonstrated along a 5-meter-long open gas cell with 1-meter resolution at 85 meters. The instrument precision is investigated by numerical simulation to anticipate the potential performance at longer range. This lidar could find applications in the French project Cigéo for monitoring radioactive waste disposal cells.

Neutral hydrogen (H i) gas content of galaxies at z ≈ 0.32

We use observations made with the Giant Metrewave Radio Telescope (GMRT) to probe the neutral hydrogen (HI) gas content of field galaxies in the VIMOS VLT Deep Survey (VVDS) 14h field at $z \approx 0.32$. Because the HI emission from individual galaxies is too faint to detect at this redshift, we use an HI spectral stacking technique using the known optical positions and redshifts of the 165 galaxies in our sample to co-add their HI spectra and thus obtain the average HI mass of the galaxies. Stacked HI measurements of 165 galaxies show that 95 per cent of the neutral gas is found in blue, star-forming galaxies. Among these galaxies, those having lower stellar mass are more gas-rich than more massive ones. We apply a volume correction to our HI measurement to evaluate the HI gas density at $z \approx 0.32$ as $\Omega_{HI}=(0.50\pm0.18) \times 10^{-3}$ in units of the cosmic critical density. This value is in good agreement with previous results at z < 0.4, suggesting no evolution in the neutral hydrogen gas density over the last $\sim 4$ Gyr. However the $z \approx 0.32$ gas density is lower than that at $z \sim 5$ by at least a factor of two.

Simulation and Experimental Study of Bipolar Plate on the Performance PEM Fuel cell

This research is a simulated and experimental study on effects of bipolar electrodes of a PEM fuel cell on its power conversion efficiency. The PEM fuel cell structure consists of bipolar electrodes, proton exchange membrane with catalysts, flow channels of gases. This research used fuel cell of 49 cm2 in active area as a research sample and the Comsol 4.4 was employed to simulate flow channels which are serpentine pattern for anode and parallel pattern for cathode. The parameters used were calculated effects of such parameters using Comsol 4.4. After the calculation has been completed, the prototype of the PEM fuel cell were fabricated using graphite plate as electrodes which had the channel height of 0.20 cm, proton exchange membrane using carbon-platinum catalyst. Finally, further it was found that the effect of temperature on the power conversion efficiency is not severely. And for anode, the concentration of hydrogen gas was reduced 64 wt% due to the reaction whereas in parallel channel of cathode the oxygen concentration was reduced by only 6 wt% from 23 wt% at the entrance to 17 wt% at the end. The maximum power output of the prototype operated under such condition was 0.28 W/cm2 calculated from maximum power output voltage (Vmp) of 0.70 V and maximum power output current density of 0.42 A/cm2 which was in good agreement with that simulated using Comsol 4.4 which revealed the power output of 0.29 W/cm2.

Efficient hydrogen sensor based on Ni-doped ZnO nanostructures by RF sputtering

We demonstrate RF sputtered Ni-doped ZnO nanostructures for detection of extremely low concentration (1ppm) of hydrogen gas at moderate operating temperature of 75°C. Structural, morphological, electrical and hydrogen sensing behavior of the Ni-doped ZnO nanostructures strongly depends on doping concentration. Ni doping exceptionally enhances the sensing response and reduces the operating temperature of the sensor as compared to undoped ZnO. The major role of the Ni-doping is to create more active sites for chemisorbed oxygen on the surface of sensor and, correspondingly, to improve the sensing response. The 4 at% of Ni-doped ZnO exhibits the highest response (∼69%) for 1% H2 at 150°C, which are ∼1.5 times higher than for the undoped ZnO. This is ascribed to lowest activation energy ∼6.47KJ/mol. Diminishing of the relative response was observed in 6% Ni- doped ZnO due to separation of NiO phase.

Nanostructure evolution of magnetron sputtered hydrogenated silicon thin films

Hydrogenated silicon (Si:H) thin films have been prepared by radio frequency (RF) magnetron sputtering. The effect of hydrogen gas concentration during sputtering on the resultant film structural and optical properties has been investigated by real time spectroscopic ellipsometry (RTSE) and grazing incidence x-ray diffraction (GIXRD). The analysis of in-situ RTSE data collected during sputter deposition tracks the evolution of surface roughness and film bulk layer thickness with time. Growth evolution diagrams depicting amorphous, nanocrystalline, and mixed-phase regions for low and high deposition rate Si:H are constructed and the effects of process parameter (hydrogen gas concentration, total pressure, and RF power) variations on the deposition rate have been qualified. Virtual interface analysis of RTSE data provides nanocrystalline volume fraction depth profiles in the mixed-phase growth regime. GIXRD measurements show the presence of (111) and (220) oriented crystallites. Vibrational mode absorption features from Si-Hn bonding configurations at 590, 640, 2000, and 2090 cm−1 are obtained by ex-situ infrared spectroscopic ellipsometry. Hydrogen incorporation decreases as films transition from amorphous to nanocrystalline phases with increasing hydrogen gas concentration during sputtering.

Enhancement of organic matter degradation and methane gas production of anaerobic granular sludge by degasification of dissolved hydrogen gas

A hollow fiber degassing membrane (DM) was applied to enhance organic matter degradation and methane gas production of anaerobic granular sludge process by reducing the dissolved hydrogen gas (D-H2) concentration in the liquid phase. DM was installed in the bench-scale anaerobic granular sludge reactors and D-H2 was removed through DM using a vacuum pump. Degasification improved the organic matter degradation efficiency to 79% while the efficiency was 62% without degasification at 12,000mgL−1 of the influent T-COD concentration. Measurement of D-H2 concentrations in the liquid phase confirmed that D-H2 was removed by degasification. Furthermore, the effect of acetate concentrations on the organic matter degradation efficiency was investigated. At acetate concentrations above 3gL−1, organic matter degradation deteriorated. Degasification enhanced the propionate and acetate degradation. These results suggest that degasification reduced D-H2 concentration and volatile fatty acids concentrations, prevented pH drop, and subsequent enhanced organic matter degradation.

Bioinspired Geometry‐Switchable Janus Nanofibers for Eye‐Readable H2 Sensors

Nanoscale architectures found in nature have unique functionalities and their discovery has led to significant advancements in various fields including optics, wetting, and adhesion. The sensilla of arthropods, comprised of unique hierarchical structures, are a representative example which inspired the development of various bioinspired systems, owing to their hypersensitive and ultrafast responsivity to mechanical and chemical stimuli. This report presents a geometry‐switchable and highly H2‐reactive Janus nanofiber (H‐NF) array inspired by the structural features of the arthropod sensilla. The H‐NF array (400 nm diameter, 4 µm height, 1.2 µm spacing distance, and hexagonal array) exhibits reversible structural deformation when exposed to a flammable concentration of hydrogen gas (4 vol% H2 in N2) with fast response times (5.1 s). The structural change can be detected with the bare eye, which is a result of change in the optical transmittance due to the structural deformation of the H‐NF array. Based on these results, an eye‐readable H2‐sensor that requires no additional electrical apparatus is demonstrated, including wetting‐controllable H2‐selective smart surfaces and H2‐responsive fasteners.

Hydrogen Gas Sensing Characteristics of Nanostructured NiO Thin Films Synthesized by SILAR Method

Nanostructured NiO thin films have been synthesized by a facile, low-cost successive ionic layer adsorption and reaction (SILAR) method, and the effects of the film thickness on their hydrogen gas sensing properties investigated. The samples were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) analysis, and energy-dispersive x-ray analysis. The XRD results revealed that the crystallinity improved with increasing thickness, exhibiting polycrystalline structure. SEM studies showed that all the films covered the glass substrate well. According to optical absorption measurements, the optical bandgap decreased with increasing film thickness. The gas sensing properties of the nanostructured NiO thin films were studied as a function of operating temperature and gas concentration. The samples showed good sensing performance of H2 gas with high response. The maximum response was 75% at operating temperature of 200°C for hydrogen gas concentration of 40 ppm. These results demonstrate that nanostructured NiO thin films synthesized by the SILAR method have potential for application in hydrogen detection.

Fabrication and Characterization Of Volatile Organic Compound Gas Sensor Based GaN Thin Film

Gas sensor using GaN film has been proposed on silicon substrate by sol gel spin coating technique with parameters growth temperature of 850°C, spinner rate of 1000 rpm, Ga2O3 molarity of 1.33 M and N sources derived from nitrogen gas at a flow rate of 100 sccm. From the results of testing the electrical properties of the gas environment type volatile organic compound, especially hydrogen gas turns electric resistance GaN semiconductor thin films declined sharply from 1.5 x 10-2 to 7 x 10-3 Ohm.cm. The GaN thin film not only exhibited good sensitivity to hydrogen gas but also showed good linearity in the characteristic of the sensitivity to hydrogen gas concentration.

SiC 기판상에 반응 스퍼터링에 의해 형성된 TiO2막의 수소가스 검지 특성

We investigated a SiC-based hydrogen gas sensor with MIS (metal-insulator-semiconductor) structure for high temperature applications. The sensor was fabricated by <TEX>$Pd/TiO_2/SiC$</TEX> structure, and a thin titanium dioxide (<TEX>$TiO_2$</TEX>) layer was exploited for sensitivity improvement. In the experiment, dependences of I-V characteristics and capacitance response properties on hydrogen gas concentrations from 0 to 2,000 ppm were analyzed at room temperature to <TEX>$400^{\circ}C$</TEX>. As the result, our sensor using <TEX>$TiO_2$</TEX> dielectric layer showed possibilities with regard to use in hydrogen gas sensors for high-temperature applications.

Hydrogen Oxidation-Mediated Current Discharge in Mesoporous Pt/TiO2 Nanocomposite.

Here we report on direct evidence of a correlation between hydrogen-to-water oxidation on mesoporous Pt/TiO2 nanocomposites at room temperature and the conversion of surface-released chemical energy into a stationary electrical current. The Pt phase of this heterojunction device is an electrically continuous 15 nm thick mesh deposited onto a mesoporous TiO2 substrate fabricated with a plasma electrolytic oxidation process. The H2O turnover frequency approaches an asymptotic value associated with the saturation of the Pt/TiO2 interface as the concentration of hydrogen gas is increased. In situ measurements of the reaction-induced current concurrently with mass spectrometry measurements illuminate the polarity switch of the reaction current (from thermionic emission to a reverse steady-state flow) simultaneously with the production of water. Furthermore, a concentration-dependent value of 5 min is measured as the time constant for the adsorption of the initial addition of H2 and H2O formation and desorption.

Room temperature hydrogen gas sensor based on palladium decorated tin oxide/molybdenum disulfide ternary hybrid via hydrothermal route

This paper demonstrates a hydrogen gas sensor based on palladium-tin oxide- molybdenum disulfide (Pd-SnO2/MoS2) ternary hybrid via hydrothermal route. The morphologies, microstructures and compositional characteristics of the Pd-SnO2/MoS2 nanocomposite were sufficiently examined by X-ray diffraction (XRD), Raman spectroscopy (RS), nitrogen sorption analysis, energy dispersive spectrometer (EDS), scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The gas-sensing performances of the Pd-SnO2/MoS2 sensor were investigated by exposed to different concentrations of hydrogen gas from 30ppm to 5000ppm at room temperature. The experimental results showed that the hydrogen gas sensor has a quite sensitive response, swift response-recovery time, good repeatability and selectivity toward hydrogen gas. Furthermore, the effect of Pd loading in the hybrid on the hydrogen gas sensing was investigated. The sensing mechanism of the Pd-SnO2/MoS2 sensor was attributed to the synergistic effect of the ternary nanostructures and the modulation of potential barrier with electron transfer. This work indicates that the as-prepared Pd-SnO2/MoS2 composite is a candidate for detecting hydrogen gas in various applications at room temperature.

Development of CanSat

AbstractA CanSat is a simulation of a real satellite, integrated within the volume and shape of a cylindrical structure. The challenge is to fit all the major subsystems found in a satellite, such as power, sensors and a communication system into this minimal volume. The CanSat is then launched to an altitude of few hundred meters by a rocket or dropped from a platform or captive balloon and its mission begins: To carry out a scientific experiment and achieve a safe landing. CanSat is composed of a Carrier and a Lander. Carrier's objective is to measure and transmit variation in Hydrogen gas concentration; change in temperature; altitude by non GPS system; GPS coordinates during its descent. Release of Lander from Carrier at an altitude of 150 m from ground, imaging in the nadir direction is the Lander's mission.

Adjustable sensitivity for hydrogen gas sensing using perpendicular-to-plane ferromagnetic resonance in Pd/Co Bi-layer films

In this work we measure hydrogen gas concentration using ferromagnetic resonance in a Pd/Co bi-layer film. The gas detection method is based on a previously demonstrated ferromagnetic resonance (FMR) peak shift which occurs in the presence of hydrogen. We find however that the maximum range of hydrogen concentrations which can normally be measured using this approach is smaller than the whole potential concentration range (i.e. 0%–100%); with the width of the accessible range being dictated by the width of the ferromagnetic resonance line. However, we demonstrate that this challenge can be addressed by exploiting the fact that the FMR peak position depends on the magnetic field applied to the sample. We show that by properly adjusting the magnetic field, overlapping sub-ranges covering a very wide range of hydrogen gas concentrations, from 0.2% to 100%, can been accessed. We speculate that a real-world broad-range device will be composed from 3 to 4 sensors, each of them tuned to a particular sub-range of concentrations and that shape-anisotropy bias can be used instead of applying external magnetic fields to the sensors.