Selective Hydrogen Gas Research Articles

Fabrication of porous silicon filled Pd/SiC nanocauliflower thin films for high performance H2 gas sensor

In this work, we have fabricated the Pd decorated silicon carbide (SiC) nanocauliflowers (NCs) thin films on electrochemically etched porous silicon (PS) substrate by DC magnetron co-sputtering technique. The gas sensing performance of Pd/SiC NCs to hydrogen gas under low (5–500 ppm) detection limit at high operating temperature regime (40–500 °C) were studied in detail without additional processing. The nanocauliflowers sensor demonstrates the high sensing response (Ra/Rg ̴ 14.48), fast response/recovery time (10s/18s) with excellent stability (24 cycles) towards 100 ppm H2 at high temperature of 380 °C. The underlying sensing mechanism behind the notable performance of the proposed sensing action towards H2 was also discussed in detail. Therefore, the investigated Pd/SiC NCs can be used as highly sensitive and selective hydrogen gas sensor at high working temperatures in harsh environment.

Hydrogen gas sensing properties of platinum decorated silicon carbide (Pt/SiC) Nanoballs

In the present study, platinum decorated silicon carbide (Pt/SiC) nanoballs (NBs) were directly grown on Ag coated porous Si substrates via DC/RF magnetron sputtering. Porous Si substrates were prepared by the metal-assisted chemical etching process at room temperature. The structural and morphological properties of as-grown SiC nanoballs (NBs) were studied using various techniques such as X-ray diffraction (XRD), Raman spectroscopy and field scanning electron microscopy (FESEM) respectively. Hydrogen gas sensing properties along with the sensing mechanism of Pt/SiC nanoball-based sensor within low detection limit (5–1000 ppm) at the high operating temperature range (30–480 °C) were investigated in detail. The sensor exhibits high sensing response (44.48%) with very fast response time (15 s) toward 100 ppm hydrogen gas at 330 °C. These above results suggest the feasibility of Pt decorated SiC nanoballs for highly sensitive and selective hydrogen gas sensor at the high operating temperature and harsh environment conditions.

Highly Sensitive and Selective Hydrogen Gas Sensor Using the Mesoporous SnO₂ Modified Layers.

It is important to improve the sensitivities and selectivities of metal oxide semiconductor (MOS) gas sensors when they are used to monitor the state of hydrogen in aerospace industry and electronic field. In this paper, the ordered mesoporous SnO2 (m-SnO2) powders were prepared by sol-gel method, and the morphology and structure were characterized by X-ray diffraction analysis (XRD), transmission electron microscope (TEM) and Brunauer–Emmett–Teller (BET). The gas sensors were fabricated using m-SnO2 as the modified layers on the surface of commercial SnO2 (c-SnO2) by screen printing technology, and tested for gas sensing towards ethanol, benzene and hydrogen with operating temperatures ranging from 200 °C to 400 °C. Higher sensitivity was achieved by using the modified m-SnO2 layers on the c-SnO2 gas sensor, and it was found that the S(c/m2) sensor exhibited the highest response (Ra/Rg = 22.2) to 1000 ppm hydrogen at 400 °C. In this paper, the mechanism of the sensitivity and selectivity improvement of the gas sensors is also discussed.

Ultra-high sensitive and selective H2 gas sensor manifested by interface of n–n heterostructure of CeO2-SnO2 nanoparticles

Detection of toxic and explosive gases in a selective manner and with higher sensitivity in industries and homes remains very challenging. Therefore, herein, we report on the ultra-high sensitive and selective hydrogen gas sensing using CeO2-SnO2 mixed oxide heterostructure synthesized by a simple hydrothermal method. The BET, photoluminescence, X-ray photoelectron spectroscopy and electron paramagnetic resonance analyses demonstrated that the CeO2-SnO2 heterostructure comprehends a high surface area and a large number of defects related to oxygen vacancies. The formation of heterojunction in CeO2-SnO2 nanostructures was confirmed by the non-linear behaviour I–V curve. The gas-sensing characteristics of the CeO2-SnO2 heterostructure showed shorter response and recovery times of approximately 17 and 24s, respectively, together with high sensitivity (19.23ppm−1) to 40.00ppm H2 gas at 300°C. The improved H2 gas sensing response of 1323 at 60ppm H2 gas is correlated with the higher surface area, pore diameter, surface defects and CeO2-SnO2 heterojunction emerging at the interfaces between the CeO2 and SnO2 serves as additional reaction sites and as well as exposed facets creating the surface to be extremely reactive for the adsorption of oxygen species. The high H2 gas selectivity observed for the CeO2-SnO2 makes them possible candidates for monitoring H2 gas at low concentrations (ppm levels).

Palladium decorated silicon carbide nanocauliflowers for hydrogen gas sensing application

Silicon carbide (SiC) nanostructures have attracted significant attention for device applications due to their unique structural, electronic and catalytic properties. Here, the efficiency of three dimensional SiC nano-cauliflowers (NCs) for hydrogen gas sensing application has been investigated. We have deposited a vertically aligned, ordered Pd decorated SiC NCs directly on a silver (Ag) coated porous anodic alumina (AAO) substrate by DC magnetron cosputtering and then it used as a gas sensor without additional processing. The sensor shows remarkably high and selective responses to hydrogen gas with low detection range 2–500ppm at relatively high temperature range (30–500°C). Our results demonstrate the potential application of Pd decorated SiC NCs for fabricating highly sensitive and selective hydrogen gas sensors.

Highly sensitive and selective hydrogen gas sensor using sputtered grown Pd decorated MnO2 nanowalls

Two-dimensional (2D) materials have attracted significant attention for device applications due to their unique structural, electronic and catalytic properties. Here, we have deposited a vertically aligned, highly ordered Pd decorated MnO2 nanowalls directly on a porous anodic alumina (AAO) by reactive sputtering and then it used as a gas sensor without additional processing. The nanowalls sensor shows remarkably high and selective responses to hydrogen gas with low detection range 10–10000ppm. Our results demonstrate the potential application of Pd decorated MnO2 nanowalls for fabricating highly sensitive and selective gas sensors.

Aerosol-Assisted CVD-Grown PdO Nanoparticle-Decorated Tungsten Oxide Nanoneedles Extremely Sensitive and Selective to Hydrogen.

We report for the first time the successful synthesis of palladium (Pd) nanoparticle (NP)-decorated tungsten trioxide (WO3) nanoneedles (NNs) via a two-step aerosol-assisted chemical vapor deposition approach. Morphological, structural, and elemental composition analysis revealed that a Pd(acac)2 precursor was very suitable to decorate WO3 NNs with uniform and well-dispersed PdO NPs. Gas-sensing results revealed that decoration with PdO NPs led to an ultrasensitive and selective hydrogen (H2) gas sensor (sensor response peaks at 1670 at 500 ppm of H2) with low operating temperature (150 °C). The response of decorated NNs is 755 times higher than that of bare WO3 NNs. Additionally, at a temperature near that of the ambient temperature (50 °C), the response of this sensor toward the same concentration of H2 was 23, which is higher than that of some promising sensors reported in the literature. Finally, humidity measurements showed that PdO/WO3 sensors displayed low-cross-sensitivity toward water vapor, compared to bare WO3 sensors. The addition of PdO NPs helps to minimize the effect of ambient humidity on the sensor response.

Selective hydrogen gas sensor using CuFe2O4 nanoparticle based thin film

Hydrogen gas sensors based on CuFe2O4 nanoparticle thin films are presented in this work. Each gas sensor was prepared by depositing CuFe2O4 thin film on a glass substrate by dc sputtering inside a high vacuum chamber. Argon inert gas was used to sputter the material from a composite sputtering target. Interdigitated metal electrodes were deposited on top of the thin films by thermal evaporation and shadow masking. The produced sensors were tested against hydrogen, hydrogen sulfide, and ethylene gases where they were found to be selective for hydrogen. The sensitivity of the produced sensors was maximum for hydrogen gas at 50°C. In addition, the produced sensors exhibit linear response signal for hydrogen gas with concentrations up to 5%. Those sensors have potential to be used for industrial applications because of their low power requirement, functionality at low temperatures, and low production cost.

Sol-Gel Derived ZnO: Nb2O5 Nanocomposite as Selective Hydrogen (H2) Gas Sensor

The present study investigates the incentive studies on phase transformations of ZnO: Nb2O5 nano composite, synthesized by sol gel protocol followed by impregnation process for sensing hydrogen gas. Detailed analyses of the synthesized nanomaterials were carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Particle size analysis. The material was subjected to different annealing temperatures ranging from 400°C to 800°C. The XRD result revealed the formation of single phase ZnNb2O6 at 700°C and above with average particle size of ∼ 67nm. ZnO: Nb2O5 based sensor has shown enhanced gas sensing properties towards 1000ppm H2 gas.

Fabrication of highly sensitive and selective H2 gas sensor based on SnO2 thin film sensitized with microsized Pd islands

Ultrasensitive and selective hydrogen gas sensor is vital component in safe use of hydrogen that requires a detection and alarm of leakage. Herein, we fabricated a H2 sensing devices by adopting a simple design of planar-type structure sensor in which the heater, electrode, and sensing layer were patterned on the front side of a silicon wafer. The SnO2 thin film-based sensors that were sensitized with microsized Pd islands were fabricated at a wafer-scale by using a sputtering system combined with micro-electronic techniques. The thicknesses of SnO2 thin film and microsized Pd islands were optimized to maximize the sensing performance of the devices. The optimized sensor could be used for monitoring hydrogen gas at low concentrations of 25–250ppm, with a linear dependence to H2 concentration and a fast response and recovery time. The sensor also showed excellent selectivity for monitoring H2 among other gases, such as CO, NH3, and LPG, and satisfactory characteristics for ensuring safety in handling hydrogen. The hydrogen sensing characteristics of the sensors sensitized with Pt and Au islands were also studied to clarify the sensing mechanisms.

Trace level detection of hydrogen gas using birnessite-type manganese oxide

A new, highly sensitive and selective hydrogen gas (H2) sensor based on birnessite-type manganese oxide (δ-MnO2) nanoflakes was prepared. The δ-MnO2 nanoflakes sensor selectively detected H2 with detection limits in air of 150ppb at 200°C and 7.5ppm at room temperature. In addition, the sensor also exhibited a considerable response to H2 in an N2 atmosphere. The sensor rapidly responded to trace levels of H2 gas and displayed reversible recovery, while the detected H2 concentrations could be accurately calculated using a modified Langmuir isotherm adsorption equation. The influence of the temperature and humidity on the sensing performance of the sensor was also investigated. The mechanism of the sensor is based on the oxidation of H2O and H2 accompanied by the formation and oxidation of MnOOH. It is believed that the low detection limit, high selectivity and fast reversible response of the δ-MnO2 nanoflake sensor are important benefits that make this sensor a promising candidate for H2 leak detection.

Selective hydrogen gas nanosensor using individual ZnO nanowire with fast response at room temperature

In this work, we report on a single ZnO nanowire-based nanoscale sensor fabricated using focused ion beam (FIB/SEM) instrument. We studied the diameter dependence of the gas response and selectivity of ZnO nanowires (NWs) synthesized by chemical vapor phase growth method. The photoluminescence (PL) measurements were used to determine the deep levels related to defects which are presented in the ZnO nanomaterial as well as to evaluate the effect of thermal treatment in H 2 atmosphere on the emission from ZnO nanowires. We show that sample annealed in hydrogen leads to passivation of recombination centers thus modifying the NWs properties. We studied the gas response and selectivity of these ZnO nanowires to H 2, NH 3, i-Butane, CH 4 gases at room temperature. Our results indicated that zinc oxide NWs hold a high promise for nanoscale sensor applications due to its capability to operate at room-temperature and its ability to tune the gas response and selectivity by the defect concentration and the diameter of ZnO nanowire. A method is proposed to reduce the nanosensor's recovery time through the irradiation with an ultraviolet radiation pulse. The sensing mechanisms of ZnO nanowires will be discussed.

A highly sensitive and selective hydrogen gas sensor from thick oriented films of MoS2

A new process is developed to fabricate a highly sensitive and selective hydrogen sensor by depositing a partially crystalline and highly oriented film of MoS2 from its single layer suspension on an alumina substrate. When these films are promoted with some catalysts selected from Pt-group metals (Pt, Pd, Ru or any combination of these metals) they exhibit a high sensitivity and selectivity to hydrogen gas. Unlike other metal oxide sensors which are sensitive to many reducing and oxidizing gases and operate at a temperature of 350 °C or higher; this sensor is highly selective to hydrogen gas and its operating temperature is from 25 to 150°C. The lower operating temperature enhances safety when dealing with hydrogen gas. The sensor response to hydrogen at 120 °C is linear in concentration from 30 to 104 ppm with a 10 to 30 second response time and a 45 to 90 second recovery time. Above 104 ppm the sensor is still linear but the slope of conductance versus hydrogen concentration changes.

A highly sensitive and selective hydrogen gas sensor from thick oriented films of MoS 2

A highly sensitive and selective hydrogen gas sensor from thick oriented films of MoS 2