Hydrogen Sensor Research Articles

(3-Aminopropyl) triethoxysilane-based immobilization of Pt/WO3 on a microfiber sensor for high sensitivity hydrogen sensing

A novel high stability hydrogen sensor based on a Pt/WO3 coated single-mode tapered-no-core single-mode (STNCS) fiber interferometer is proposed and experimentally studied. The STNCS structure is treated by (3-Aminopropyl) triethoxysilane (APTES) and then coated with Pt/WO3 nanorods. Compared to the traditional method of using poly (dimethylsiloxane) (PDMS) to adhere Pt/WO3 nanorods on the fiber surface, the APTES modified fiber forms strong covalent bonds with Pt/WO3 with stronger adhesion to the fiber surface, resulting in improved long-term stability. Experimental results show that the sensitivity of the sensor varies from − 31.05 nm/% to − 4.30 nm/% as the hydrogen concentration increases from 0% to 1.04%. The sensor also demonstrates good reproducibility, longer term stability and repeatability.

High Sensitivity Hydrogen Sensors Based on Optical Micro/Nanofiber Couplers Working at the Dispersion Turning Point

The safe utilization of hydrogen as a clean fuel and industry material requires the reliable detection of gas leakage. Thus, hydrogen sensors with high sensitivity and fast response are in urgent demand. Optical hydrogen sensors are especially attractive among various hydrogen detection techniques because of their intrinsic safety. Herein, a high-sensitivity hydrogen gas sensor is proposed based on optical micro/nanofiber couplers working at the dispersion turning point. The Pd coatings used were deposited on the waist region by magnetron sputtering. Due to the phase transition of palladium in the presence of hydrogen, intensity changes in the optical transmission of the devices are produced. It is demonstrated that the proposed platform provides high sensitivity, good repeatability, and selectivity, together with a fast response time for hydrogen detection below the explosive concentration. The response and recovery times are ~20 and ~28 seconds, respectively. The detected hydrogen concentration range is 0.1-1.5% (in volume). The detection limit of this sensor is below 0.1%.

All-optical non-contact level sensor for liquid hydrogen

We propose a new type of liquid hydrogen level sensor and evaluate a prototype system with liquid nitrogen. The level sensor acquires images of the liquid surface, which is illuminated by point sources of light, and estimates the liquid level by image processing. This scheme allows us to avoid immersion of the sensor body into the liquid and also eliminate the necessity for any electrical wire connected to the sensor body. The accuracy of the prototype sensor is estimated to be ≈ 4.8 mm in our experiment using a 10 liter liquid nitrogen vessel.

A Chemical Synthesis of CdSnO 3 Nanoparticles and their Performance in Hydrogen Sensing

Abstract: CdSnO3 nanoparticles were successfully synthesized without any templates by simple co-precipitation synthesis route. Further characterized by using X-ray diffraction (XRD) measurements, field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR) spectroscopy and their hydrogen sensing properties were investigated. The CdSnO3 nanoparticles exhibited outstanding gas sensing characteristics such as, higher gas response, extremely rapid response, fast recovery, excellent repeatability, good selectivity and at ambient operating temperature (~ 30C). Furthermore, the CdSnO3 nanoparticles can detect up to 5 ppm for hydrogen with reasonable sensitivity at an ambient operating temperature.

Kinetics-Driven Dual Hydrogen Spillover Effects for Ultrasensitive Hydrogen Sensing.

Palladium (Pd)-modified metal oxide semiconductors (MOSs) gas sensors often exhibit unexpected hydrogen (H2 ) sensing activity through a spillover effect. However, sluggish kinetics over a limited Pd-MOS surface seriously restrict the sensing process. Here, a hollow Pd-NiO/SnO2 buffered nanocavity is engineered to kinetically drive the H2 spillover over dual yolk-shell surface for the ultrasensitive H2 sensing. This unique nanocavity is found and can induce more H2 absorption and markedly improve kinetical H2 ab/desorption rates. Meanwhile, the limited buffer-room allows the H2 molecules to adequately spillover in the inside-layer surface and thus realize dual H2 spillover effect. Ex situ XPS, in situ Raman, and density functional theory (DFT) analysis further confirm that the Pd species can effectively combine H2 to form Pd-H bonds and then dissociate the hydrogen species to NiO/SnO2 surface. The final Pd-NiO/SnO2 sensors exhibit an ultrasensitive response (0.1-1000ppm H2 ) and low actual detection limit (100 ppb) at the operating temperature of 230 °C, which surpass that of most reported H2 sensors.

Improved performance of fiber-optic hydrogen sensor of porous Pt/WO3 based on ZIF-8

A novel fiber-optic hydrogen sensor including Pt/WO3 sensing material with a microporous structure is proposed and experimentally demonstrated with improved performance. The proposed Pt/WO3 sensing material is realized by introducing metal-organic frameworks (MOFs) as templates. The mesoporous structure of the ZIF-8 template improves the reactive sites of hydrogen sensitive materials with hydrogen. Hydrogen sensors were fabricated by combining the synthesized material with Fiber Bragg Gratings (FBGs) and the performance of hydrogen sensors was investigated. The experimental results show that the hydrogen sensitivity of the FBG with ZIF-8 synthesized Pt/WO3 has been increased to 0.075 pm/ppm, which is twice that without ZIF-8 synthetization. The stability and the response speed are also significantly improved. The introduction of microporous MOFs templates into Pt/WO3 sensing material will greatly accelerate the wide application of Pt/WO3-based fiber optic hydrogen sensors on hydrogen leakage detection.

Promoting the discoloration of PdO in low concentration H2 by using PdAu bimetallic catalyst for eye-readable hydrogen leakage detection

Developing reliable and low-cost optical hydrogen sensors for hydrogen leakage detection at room temperature is extremely important. It requires that hydrogen sensors have a remarkable and rapid color change in low concentration H2/air mixtures, which it is still quite challenging at present. Herein, we demonstrate an eye-readable hydrogen sensor based on Pd-decorated Au@PdO core-shell nanoparticle arrays (Pd-Au@PdO NAs). Pd-Au@PdO NAs show an obvious color change from brownish-yellow to yellow-gray in 1 v/v% H2/air and gray in 4 v/v% H2/air, with ΔE values of 8.1 and 22.5, respectively. Detailed investigation showed that, at the cracks of PdO shell where Au core is exposed, PdAu bimetallic catalyst is generated during the sample-synthesis process. Compared with Pd catalyst, PdAu bimetallic catalyst significantly prompts the reduction of PdO in low concentration H2, represented as a faster discoloration process and more obvious color change. Additionally, the core-shell structure ensures a long-term stability through protecting the PdAu catalyst. We further show that the irreversible sensing performance of Pd-Au@PdO NAs can be reactivated repeatedly, which favors extending the lifetime of the optical sensor and reducing the cost.

A taper-in-etch based hybrid fiber Mach-Zehnder interferometer hydrogen sensor

A hydrogen (H2) sensing application is proposed and experimentally demonstrated using a multimode fiber (MMF)–tapered-in-etch single-mode fiber (SMF)–MMF (MMF–TiESMF–MMF)-based Mach–Zehnder interferometer (MZI). The MZI is made of an SMF segment placed between two MMF segments. The MMF segments function as mode couplers, splitting and combining light due to a core diameter discrepancy between the MMF and the SMF. The SMF segment undergoes cladding modification by chemically etching to achieve a 50 µm diameter over a 2 cm length, followed by the tapering to obtain a 15 µm waist diameter with a 1 cm length. A layer of palladium–graphite nanofibers is applied to the modified area of the TiESMF to produce H2 adsorption. The sensor is investigated against H2 over the 0.25–1% concentration range at room temperature. When H2 molecules were desorbed on the sensing layer, its index of refraction was changed so that the output spectrum resulting from the MZI is blue-shifted due to H2 molecules desorption. The MMF-TiESMF-MMF MZI exhibits a sensitivity of 0.332 nm/vol% and a linear fit coefficient of 99.72% for H2 concentrations in the range selected. MZI based sensors showed a linear, stable, and repetitive response.

Photothermal contributions to H–Pd system

Temperature is one of the most critical parameters to control reaction process, increasing reaction temperature can promote the activity of the catalyst. Thus, a high priority will be to effectively accelerate the chemical reaction and improve the efficiency of chemical reaction by using appropriate means to raise reaction temperature. Herein, hydrogen-palladium (H–Pd) reaction, as a reversible reaction, is the internal physicochemical mechanism of Pd-catalyzed hydrogen purification and Pd-based hydrogen detection. According to temperature dependence of H–Pd reaction, it is significance to develop an H–Pd reaction temperature enhancement scheme to accelerate reaction and improve reaction efficiency, which is important to design/optimize Pd-based hydrogen sensor and understand the relationship between reaction course and temperature. Therefore, we demonstrate an all-optical H–Pd reaction temperature enhancement scheme assisted by photothermal effect. In addition, for analyzing the relation between H–Pd reaction and temperature, we designed an optics-mechanics coupling-based fiber hydrogen sensor, it can convert the influence of photothermal-induced reaction temperature raising on H–Pd reaction to its hydrogen response. These experimental results demonstrate that this proposed photothermal effect-assisted reaction temperature enhancement scheme can be used as an effective strategy to improve H–Pd reaction, and it has the great potential to achieve significant performance improvements of hydrogen detection.

MEMS sensor based on MOF-derived WO3-C/In2O3 heterostructures for hydrogen detection

Rational structure design of sensing materials is the most effective way to obtain a hydrogen (H2) sensor with optimal performance. Herein, a porous heterostructure WO3-C/In2O3 was designed and prepared by in-situ coupling carbon layer and WO3 into MOF-derived (metal organic framework) In2O3. In combination with Micro-Electro-Mechanical System (MEMS), a miniature H2 sensor using WO3-C/In2O3 as the active sensing material was fabricated. Compared with the bare In2O3 sensor, the sensor based on WCI-9 (the mass ratio of WO3 to In2O3 in WO3-C/In2O3 is 9 wt%) shows higher response value and lower operating temperature (Ra/Rg = 10.11@ 1000 ppm; 250 °C). Moreover, the WCI-9 sensor possesses a fast response-recovery speed (1.9/9.2 s@200 ppm) and a low limit of detection (LOD) (5 ppm) for H2. The good performance of the WCI-9 sensor is attributed to the hierarchical porous structure and multicomponent heterojunctions present in the material. This work not only provides an effective method for H2 detection, but also a strategy for constructing sensing materials with multicomponent heterojunctions.

Room Temperature Resistive Hydrogen Sensor for Early Safety Warning of Li-Ion Batteries

Lithium-ion batteries (LIBs) have become one of the most competitive energy storage technologies. However, the “thermal runaway” of LIBs leads to serious safety issues. Early safety warning of LIBs is a prerequisite for the widely applications of power battery and large-scale energy storage systems. As reported, hydrogen (H2) could be generated due to the reaction of lithium metal and polymers inside the battery. The generation of H2 is some time earlier than the “thermal runaway”. Therefore, the rapid detection of trace hydrogen is the most effective method for early safety warning of LIBs. Resistive hydrogen sensors have attracted attention in recent years. In addition, they could be placed inside the LIB package for the initial hydrogen detection. Here, we overview the recent key advances of resistive room temperature (RT) H2 sensors, and explore possible applications inside LIB. We explored the underlying sensing mechanisms for each type of H2 sensor. Additionally, we highlight the approaches to develop the H2 sensors in large scale. Finally, the present review presents a brief conclusion and perspectives about the resistive RT H2 sensors for early safety warning of LIBs.

Construction of ultra-fast hydrogen sensor for dissolved gas detection in oil-immersed transformers based on titanium dioxide quantum dots modified tin dioxide nanosheets

Hydrogen (H2) is a typical product dissolved in transformer oil and a typical fault diagnosis gas for oil-immersed transformer equipment. The large concentration range and fast detection of H2 gas sensors have certain engineering significance. In this paper, TiO2 quantum dots (QDs) with particle size of about 5 nm were prepared by solvothermal reaction, and SnO2 nanosheets modified by TiO2 QDs was successfully prepared. The gas sensing performance of TiO2-SnO2 to H2 was systematically explored. The optimal operating temperature of the sensors is 400 °C. At the optimal operating temperature of 400 °C, the TiO2 (1 %)-SnO2 sensor demonstrated the most excellent gas sensing performance to H2, such as the short response and recovery time (2 s and 5 s to 200 ppm H2), excellent stability, outstanding selectivity and large detection range of 4.8–5000 ppm. The first-principles calculations were carried out and the gas sensing mechanism was further elaborated, which show that the improvement of the TiO2(1 %)-SnO2 is mainly ascribed to the sensitization and homojunction effect of TiO2 QDs. The TiO2 (1 %)-SnO2 gas sensor is expected to provide a choice for the dissolved gas analysis (DGA) method in transformer oil analysis.

Surface modification of nanosheet-type tin oxide with Au-Pd for hydrogen gas sensing

A thin film consisting of a nanosheet-type tin oxide (SnO2) was synthesized on a sensor chip via the aqueous solution process. Au-Pd was then loaded on its surface via ion sputtering. The sensor signal response of the Au-Pd loaded nanosheet-type tin oxide to hydrogen was higher than that of the bare nanosheet-type tin oxide, while its signal response to methane gas decreased. The 42% covered nanosheet-type tin oxide (30 s sputtering) resulted in the highest H2/CH4 response ratio. The high sensor signal response to hydrogen was attributed to the hydrogen spill-over effect, the oxygen back spill-over effect, and the (101) crystal facet on the surface of the nanosheet-type tin oxide. The designed nanosheet has potential applications as a hydrogen sensor array.

A Review of Hydrogen Sensors for ECLSS: Fundamentals, Recent Advances, and Challenges

The development of hydrogen sensors with high detection accuracy, fast response times, long calibration periods, and good stability has become the focus of the space station environmental control and life support subsystem. We analyze the current research status of different types of hydrogen sensors, including catalyst combustion type, heat conduction type, semiconductor type, fiber optic type, etc. The response signals of most hydrogen sensors are affected by temperature and humidity, resulting in cross-sensitivity. Reducing the cross-sensitivity of temperature, humidity, and other interfering factors to achieve accurate hydrogen measurement in different environments is a challenge that limits the development of hydrogen sensors. Several hydrogen sensors that are currently commercially available have a narrow operating temperature range, most of them can only measure at room temperature, and high-temperature environments require a higher accuracy and lifetime of the sensor than required at room temperature. Many new hydrogen-sensitive materials were developed to improve the performance of the sensors. The excellent performance of fiber-optic hydrogen sensors is beneficial to temperature compensation and distributed multiparameter measurement, as well as to the research and development of intelligent sensing systems, in the context of the Internet of Things. The signal detection and demodulation techniques of fiber-optic sensors are the focus of future hydrogen sensor research.

Multi-point optical fiber hydrogen detection system based on light polarization modulation

A hydrogen sensing system including 8 sensors based on light polarization modulation is developed and demonstrated for simultaneous multi-point hydrogen sensing with high sensitivity. Each sensor is composed of a polarizer, a polarization control, and a short segment of polarization maintaining fiber (PMF) coated with Pt-loaded WO3. Due to the exothermic reaction between hydrogen and WO3 with the help of catalyst Pt, the local temperature of PMF increases and the reflective spectrum of the sensor shift accordingly. The self-developed control system software achieves the sequential scanning and recording of the reflection spectra of each sensor by programable controlling a light switch, and then gives the measured hydrogen concentration of each channel in real-time according to the spectrum shift by using an automatic dip finding algorithm with Gaussian fitting. The experimental results show that the proposed type of sensor has ultra-high hydrogen sensitivity, with a maximum value of −20.22 nm/% (vol %); packaging with foam substrate helps to reduce the response time of the device; the hydrogen sensor is almost unaffected by environmental relative humidity. Moreover, the hydrogen sensing system is experimentally proved having good stability and repeatability.

Selective Deposition of PdO Nanoparticles on Si Nanodevices for Hydrogen Sensing

In this paper, we present a method, involving plasma-enhanced atomic layer deposition and constant-power device-localized Joule heating (DLJH), for the selective deposition of palladium oxide (PdO) nanoparticles at the n– region of n+/n–/n+ polysilicon nanobelt (PNB) devices. These PdO-decorated PNB devices were then operated under DLJH so that the temperature of the n– region was maintained during the sensing of H2 gas. From their measured responses, the devices operated at a temperature of 339 K exhibited the most reactive interactions between PdO and H2. Considering the possibility of humidity interference, we also characterized the PdO-decorated PNB devices for H2 sensing at various relative humidities. The PdO nanoparticles on the PNB devices having a grain distance that sustained a spillover effect were almost immune to RH interference.

Printed, Flexible, Ionic Liquid-Based Hydrogen Sensor via Aerosol Jet Printing of Nanomaterials

Low-cost, high-performance hydrogen sensors are highly demanded in hydrogen leakage detection. To increase the sensitivity and reliability of the hydrogen sensor, an ionic liquid (IL)-based electrochemical gas sensor is fabricated with bimetallic Platinum–Nickel (Pt-Ni) nanoparticles (NPs) with aerosol jet printing technology for continuous monitoring of hydrogen concentration. The Pt-Ni NPs covering the top surface of the metal electrodes can accelerate the catalysis and expand the sensing surface area. When hydrogen gas is sensed at room temperature, the uniquely reversible and rapid redox reactions of hydrogen at the IL/Pt electrode interface, thereby creating continuous measurement capability in a real-time manner with little signal drift. The full coverage of the sensor electrodes will increase the robustness and accuracy of the device. The fabricated sensors demonstrate excellent analytical sensing performance, reaching a limit of detection up to 19.3 ppm. The device takes advantage of an easy fabrication process, simple structure, high sensing response, and low cost, providing a promise for hydrogen sensing at room temperatures.

The Effect of the Working Electrode Material Based on Pt/SnO2(Sb) on the Properties of Hydrogen and Carbon-Monoxide Sensors

The effect of the platinum content (3–10 wt %) in the Pt/SnO2(Sb)-based working-electrode material on the properties (sensitivity, high-speed performance, recovery time) of solid-state potentiometric gas sensors for hydrogen and carbon monoxide including their simultaneous presence in air is studied. Sensors with 5% Pt demonstrate the best characteristics: the efficient carbon-monoxide detection for its concentration from 0.01 to 1 vol %; no effect of hydrogen present in the CO + air mixture in concentrations comparable with the CO concentration; the shortest relaxation time (~30 s at 1% CO).

The Effect of the Working Electrode Material Based on Pt/SnO2(Sb) on the Properties of Hydrogen and Carbon-Monoxide Sensors

The Effect of the Working Electrode Material Based on Pt/SnO2(Sb) on the Properties of Hydrogen and Carbon-Monoxide Sensors

Monolithic Three-Dimensional Integration of Carbon Nanotube Circuits and Sensors for Smart Sensing Chips.

Semiconducting carbon nanotube (CNT) film is a promising material for constructing high-performance complementary metal-oxide-semiconductor (CMOS) integrated circuits (ICs) and highly sensitive field-effect transistor (FET) bio/chemical sensors. Moreover, CNT logic transistors and sensors can be integrated through a compatible low-temperature fabrication process, providing enough thermal budget to construct monolithic three-dimensional (M3D) systems for smart sensors. However, an M3D sensing chip based on CNT film has not yet been demonstrated. In this work, we develop M3D technology to fabricate CNT CMOS ICs and CNT sensor arrays in two different layers; then, we demonstrate a preliminary M3D sensing system comprising CNT CMOS interfacing ICs in the bottom layer and CNT sensors in the upper layer through interlayer vias as links. As a typical example, a highly sensitive hydrogen sensing IC has been demonstrated to perform in situ sensing and processing functions through upper-layer FET-based hydrogen sensors exposed to the environment and bottom-layer CNT CMOS voltage-controlled oscillator (VCO) interfacing circuits. The M3D CNT sensing ICs convert hydrogen concentration information (8-128 ppm) to digital frequency information (0.78-1.11 GHz) with a sensitivity of 2.75 MHz/ppm. M3D sensing technology is expected to provide a universal sensing system for future smart sensing chips, including multitarget detection and ultralow power sensors.