Hydrogen Gas Sensor Research Articles

1 ppm-detectable hydrogen gas sensor based on nanostructured polyaniline

The hydrogen (H2) energy industry has continued to expand in recent years due to the decarbonization of the global energy system and the drive towards sustainable development. Due to hydrogen’s high flammability and significant safety risks, the efficient detection of hydrogen has become an increasingly hot issue today. In this work, a new type of relatively fast and responsive conducting polymer sensor has been demonstrated for tracing H2 gas in a nitrogen environment. Inspiration of unique properties of carbon nanotube (CNT) and graphene, polyaniline (PANI) hollow nanotubes, PANI thin films are fabricated to study for structural-properties investigation. The PANI hollow nanotube sensor ensures the 1 ppm hydrogen gas detection at room temperature, and exhibits high sensitivity (29%) and fast response and recovery times of 15 and 17 s, follows by PANI thin film sensor (20%), response and recovery times of 65s and 45s. This conducting polymer-based hydrogen sensor holds promise for the early detection of H2 leaks in a wide range of industries.

Nano‐Patterned CuO Nanowire Nanogap Hydrogen Gas Sensor with Voids

AbstractHydrogen (H2) is increasingly employed in industrial applications, such as developing hydrogen fuel cells for vehicles and power plants. However, H2 explodes at a concentration limit of 4%, necessitating the development of ultrasensitive hydrogen sensors capable of early‐stage detection of hydrogen leaks. In this study, nano‐patterned polycrystalline cupric oxide (CuO) nanowire array nanogap gas sensors with voids are fabricated using electron‐beam lithography and ex situ oxidization by annealing, which could detect 5 ppb H2 and show response and recovery times of less than 10 s without a baseline shift. Combining a pre‐H2 annealing process in Ar/H2 for Cu nanowires and a low‐rate oxidation process enhances the crystallinity of CuO nanowires, facilitating the preparation of polycrystalline CuO nanowires with voids, which is a significantly practical approach for the improvements of gas sensing properties. Response and recovery times of <10 s can be obtained for a gap separation of ≈30 nm. These improvements are discussed based on a high electric field of ≈1.3 MV cm−1. The relationship between the normalized response and H2 concentration is discussed based on the power law. This paper presents highly reliable and fast H2 sensors without a baseline shift to meet the demands of the hydrogen industry.

Study of argon plasma modified Pd/AlGaN/GaN high electron mobility transistor for superior hydrogen gas detection

The surface and microstructure of the sensitive material play an important role in the gas adsorption and detection. However, few report of the surface modification affection on the work function-based gas sensor is carried out. Herein, facile Ar+ modification is proposed and utilized to modify the surface of the Pd sensitive layer, which acts as the gate of a AlGaN/GaN high electron mobility transistor (HEMT) based hydrogen (H2) gas sensor. Results show that the Pd surface is significantly changed to smoother microstructure by 5 s Ar+ modification. Compared with the device without Ar+ modification, the response values increase by ∼ twice at all operating temperatures. Interestingly, the response time is pronouncedly shortened from 10 to 2.3 s at 500 ppm, suggesting the significant effect of Ar+ modification in the enhancement of gas detection. At the optimized operating temperature of 120 °C, a high response of 739% and an ultrafast response time of 1.4 s are observed for the 500 ppm H2 gas. In addition, this sensor exhibits a low limit of detection ∼200 ppb, along with excellent repeatability, consistency, and selectivity. Our study indicates that the facile Ar+ modification of the gate surface is a highly effective technology in the enhancement of gas detection and may provide a novel approach for the design and development of all the work function type gas sensors.

(Invited) Development of Fiber-Optic Hydrogen Sensor Using Platinum-Supported Tungsten Trioxide-Silica Composite Film

A fiber-optic hydrogen gas sensor using a platinum-supported tungsten oxide-silica composite film was fabricated. This sensor utilizes the absorption of the evanescent field interaction in the hydrogen sensitive clad which was composed of WO3 and SiO2, coated on a silica core with sol-gel process. As a first step, transmission spectra of sensing film itself were measured. The transmittance of the sensitive film decreased in the range of wavelengths above about 500 nm after exposure to pure hydrogen, and the change in transmittance at 1300 nm was greater than that at 850 nm. Then, fiber optic sensor device was fabricated, and the amount of propagating light was measured. In the case of using the light source with a wavelength of 1300 nm, the sensitivity with respect to the hydrogen response was nearly twice and the response speed was faster, compared with those at 850 nm.

Developing an internet of things system for hydrogen leak detection at hydrogen refueling stations integrating LoRa and global positioning system

Developing a hydrogen leak detection system that can quickly detect even the smallest amount of hydrogen is extremely crucial in the hydrogen industry. Currently, hydrogen refueling stations use a fixed hydrogen leak detection system. This study develops a mobile hydrogen gas leak detection system for hydrogen refueling stations using s, global positioning system, and Internet of Things (IoT) equipment, including LoRa and Wi-Fi. A digital twin is implemented by linking hydrogen gas-sensing data at a location that is quickly required or suspected using Google Maps. A time-series database is used to store the hydrogen gas-sensing data, and the transfer delay of hydrogen gas-sensing data between the hydrogen equipment was measured. Therefore, we developed a prototype system that transmits, stores, and analyzes hydrogen gas-sensing data in real time using IoT equipment for hydrogen refueling stations.

One-Dimensional ZnO Nanorod Array Grown on Ag Nanowire Mesh/ZnO Composite Seed Layer for H2 Gas Sensing and UV Detection Applications.

Photodetectors and gas sensors are vital in modern technology, spanning from environmental monitoring to biomedical diagnostics. This paper explores the UV detection and gas sensing properties of a zinc oxide (ZnO) nanorod array (ZNA) grown on silver nanowire mesh (AgNM) using a hydrothermal method. We examined the impact of different zinc acetate precursor concentrations on their properties. Results show the AgNM forms a network with high transparency (79%) and low sheet resistance (7.23 Ω/□). A sol-gel ZnO thin film was coated on this mesh, providing a seed layer with a hexagonal wurtzite structure. Increasing the precursor concentration alters the diameter, length, and area density of ZNAs, affecting their performance. The ZNA-AgNM-based photodetector shows enhanced dark current and photocurrent with increasing precursor concentration, achieving a maximum photoresponsivity of 114 A/W at 374 nm and a detectivity of 6.37 × 1014 Jones at 0.05 M zinc acetate. For gas sensing, the resistance of ZNA-AgNM-based sensors decreases with temperature, with the best hydrogen response (2.71) at 300 °C and 0.04 M precursor concentration. These findings highlight the potential of ZNA-AgNM for high-performance UV photodetectors and hydrogen gas sensors, offering an alternative way for the development of future sensing devices with enhanced performance and functionality.

Ce Doping Effects on the Hydrogen Sensing Properties of Graphene/SnO2-Based Sensors.

The development of a sensor capable of selectively detecting hydrogen levels in the environment holds immense importance for ensuring the safer utilization of hydrogen energy. In this study, a hydrogen sensor made of Ce-doped single-layer graphene (SLG)/SnO2 composite material was fabricated using a hydrothermal method. The study examined the impact of varying Ce doping concentrations on the hydrogen sensing capabilities of the SLG/SnO2 matrix. The results show that the SLG/SnO2 hydrogen sensor doped with 2 mol% Ce demonstrated optimal performance at a humidity of 20%. It operated most efficiently at 250 °C, with a response of 2.49, representing a 25.75% improvement over the undoped sample. The response/recovery times were 0.46/3.92 s, which are 54.9% shorter than those of the undoped sample. The enhancement in hydrogen sensitivity stems from the synergistic effect of Ce and SLG, which facilitates the coexistence of n-n and p-n heterojunctions, thereby increasing carrier mobility and refining grain structure. Analysis via X-ray photoelectron spectroscopy (XPS) reveals that Ce increases the material's oxygen vacancy concentration, enhancing its hydrogen sensitivity. Ce-doped SLG/SnO2, with its robust hydrogen sensitivity, represents one of the leading candidates for future hydrogen gas sensors.

Hydrogen gas sensor based on NiO decorated macroporous silicon heterojunction

Hydrogen gas sensor based on NiO decorated macroporous silicon heterojunction

Optimization for hydrogen gas quantitative measurement using tunable diode laser absorption spectroscopy

Gas sensors are vital for safety, quality control, and environmental preservation across diverse industries. Tunable diode laser absorption spectroscopy (TDLAS) is widely employed for gas analysis due to its high sensitivity and selectivity. However, quantifying low concentrations of hydrogen gas using TDLAS in the infrared region proves challenging due to its lower absorption compared to other gases in the NIR region. This study introduces an innovative method for precise hydrogen gas measurement through the analysis of absorption spectra at different pressures and the employment of a high-pressure gas cell. By applying these methodologies to a calibration-free technique, we can realize the optimal measurement conditions for increasing the gas detection limit and stabilizing the wavelength lock for the laser diode. As a result, a linear relationship between hydrogen gas concentration and sensor response is achieved in the wide detection range of 0.01% to 100%. Under the optimal measurement conditions, our TDLAS system’s stability is demonstrated with minimum detection limits of 0.2866% and 0.0055% at integration times of 1 s and 30 s, respectively.

(Invited) Ga2O3 Semiconductor Devices for High-Temperature Operation

Beta phase of gallium oxide (Ga2O3) has attracted a lot of attention as an ultra-wide band gap semiconductor for applications in high-power electronic devices. High power operation often comes with increased temperatures of the devices due to joule heating, especially in semiconductors like Ga2O3with low thermal conductivity. However, electrical performance and reliability of the Ga2O3based diodes and transistors at very high temperature, above 400C, is not well established.In this talk, I will present our recent experimental results on fabrication of Ga2O3semiconductor devices for applications as high-temperature diodes and hydrogen gas sensors. The fabricated Ga2O3/NiO p-n heterojunctions allow for device operation with >100-1000 rectification ratio up to 400-600C [1]. Despite the stable ultrathin Ohmic contact [2], the device performance degrades over tens of temperature cycles and hundreds of hours at these elevated temperatures, likely due to instability of the rectifying contact. We propose and implement alternative interfacial rectifying contact layers, that enable both high performance and long reliability of these high temperature Ga2O3 semiconductor devices.[1] Sohel, Zakutayev et al Physica Status Solidi (a) 220 2300535 (2023)[2] Callahan, Zakutayev et al J. Vac. Sci. Technol. A 41, 043211 (2023)

Pure 3D Conducting Polymer Network for an Ultra-Sensitive and Flexible Hydrogen Gas Sensor at Room Temperature

Hydrogen (H2) is considered a next-generation energy source with diverse applications across valuable social, economic, and industrial sectors, including transportation, biomedical, power generation, and space exploration. Due to its low ignition energy and wide flammable range, there is an urgent global demand for ultrasensitive, lightweight, portable, wearable, and flexible hydrogen sensors to identify early gas leaks and prevent environmental and economic implications.In this study, we present a flexible hydrogen gas sensor based on conducting polymers, namely polypyrrole (PPY) with graphene nanoparticles, synthesized by the bi-continuous microemulsion polymerization method. The one-step scalable synthetic procedure enables the design of 1D, 2D, and 3D conducting polymers and their nanocomposites with tunable morphological and electrical properties. The unique multilayered oil-to-water nature of the bi-continuous microemulsion allows the fabrication of pure mesoporous 3D conducting polymers and their composites without the addition of any cross-linkers with excellent electrical properties. The 3D pure porous polymer network acts as a monolithic conducting framework that facilitates electron and ion transport and promotes the diffusion of molecules and ions more efficiently than 1D or 2D structures. The soft and porous nature of the polymer improves the interaction and adsorption of the target gas molecules and sensing material by increasing the number of active sites.This 3D PPY_graphene flexible network synthesized by the bi-continuous microemulsion method is successfully utilized to fabricate an ultra-sensitive flexible gas sensor. The performance of the sensor can be modified based on the reactor design. The sensor exhibits a notable response to 1 ppm of H2 gas. At room temperature, the fabricated sensor displayed 14 and 20 seconds of response and recovery time, respectively. To the best of our knowledge, no study has explored the application of 3D pure conducting polymers and their nanocomposites for hydrogen gas sensors using the bi-continuous microemulsion polymerization method, yielding such exceptional sensing results. Figure 1

Size dependent dual functionality of CeO2 quantum dots: A correlation among parameters for hydrogen gas sensor and pollutant remediation

The metal oxide-based nanostructures of variable size and shape are found effective in optimizing the gas sensing ability and pollutant degradation. The size induced lattice strain and large band gap in 3nm CeO2 quantum dots evolved the ability towards hydrogen gas sensing and dye degradation compared to nanopebbles and nanoparticles of sizes 15 ± 3, and 30 ± 12 nm. The smaller CeO2 quantum dots than Debye length was found underlying reason for nearly four times sensor response and selectivity towards reducing hydrogen gases than the oxidizing gases at 1–10 ppm level. The lattice strain calculated by Rietveld refinement and W–H analysis was found in-line with the size of CeO2 nanostructures. The enhancement in lattice strain and optical band gap (2.66, 2.78, and 2.89 eV) with decrease in size are found critical for determining the overall efficiency of CeO2 nanostructures for photocatalytic activity, attributed to the strong quantum confinement effect. The higher catalytic activity of 98 % was achieved CeO2 quantum dots in comparison to the 95 % and 94 % obtained for CeO2 nanopebbles and nanoparticles. The impact of change in degradation efficacy and gas sensing ability of different CeO2 nanomaterials is discussed in detail. This work offers a novel and simplistic method to produce CeO2 quantum dots as an efficient sensor for selective detection of H2 gas and photocatalyst. The correlation between size, Debye length, band gap, and lattice strain gives an insight for understanding the underlying detection mechanism for selective detection of reducing gas molecules and efficient pollutant remediation.

Investigation on palladium gate electrode-based SOI junctionless FET for hydrogen gas sensing

This study provides a comprehensive investigation on palladium (Pd) gate electrode-based silicon on insulator (SOI) junctionless field-effect transistor (JLFET) for hydrogen gas (H2) sensing (Pd–SOI-JLFET). The device has a gate dielectric stack consisting of silicon dioxide (SiO2) and hafnium dioxide (HfO2). An extensive analysis was conducted to detect and identify the presence of hydrogen gas by examining several electrical characteristics such as drain current (IDS), transconductance (gm), output conductance (gd), energy band diagram (E), gate-to-source capacitance (CGS), and surface potential (Φs). Furthermore, a comprehensive investigation was conducted to examine the impact of the presence of H2 gas and variations in temperature on important parameters associated with the short channel effects (SCEs) including off-state current (IOFF), on-state current (ION), subthreshold swing (SS) and threshold voltage (Vth). In addition, the sensitivity analysis of the off-state current (IOFF) by considering process variation effect has been done. Sensitivity is also calculated at various temperatures for the detection of hydrogen gas molecule. At the temperature of 300K, the sensitivity values were obtained as 1.50083, 3.21754, 27.71483, 152.39617 and 2052.8 for pressure values 10−14 Torr, 10−13 Torr, 10−12 Torr, 10−11 Torr and 10−10 Torr, respectively. This analysis provides a thorough examination of the performance and efficacy of the Pd–SOI-JLFET hydrogen gas sensor highlighting its potential for a wide range of hydrogen sensing applications.

High responsive Pd decorated low temperature α-MoO3 hydrogen gas sensor

The H2 gas adsorption properties, which are the most crucial concept for a gas sensor, of the 2-dimensional (2D) MoS2 are limited compared to its oxide form of 2D α-MoO3. On the other hand, it is straightforward to form high surface-to-volume ratio nanostructures with MoS2. In order to get the benefits of the large surface and better H2 adsorption properties for the H2 gas sensor, MoS2 film grown by the chemical vapor deposition (CVD) method was converted into MoO3 with a thermal oxidation process at 380 °C under oxygen-ambient conditions. The grown MoS2 film has indicated that it is formed from the coalesced MoS2 flakes. An ultra-high response of 3 × 106 at a relatively low temperature of 100 °C was achieved for as low as 800 ppm hydrogen concentration. The hydrogen gas sensing mechanism has been discussed in depth using the double injection model, similar to the electrochromic mechanism.

Pd Nanoparticles Decorated Hollow TiO2 Nanospheres for Highly Sensitive and Selective UV-Assisted Hydrogen Gas Sensors

Pd Nanoparticles Decorated Hollow TiO₂ Nanospheres for Highly Sensitive and Selective UV-Assisted Hydrogen Gas Sensors

Balancing Pd-H Interactions: Thiolate-Protected Palladium Nanoclusters for Robust and Rapid Hydrogen Gas Sensing.

The transition toward hydrogen gas (H2) as an eco-friendly and renewable energy source necessitates advanced safety technologies, particularly robust sensors for H2 leak detection and concentration monitoring. Although palladium (Pd)-based materials are preferred for their strong H2 affinity, intense palladium-hydrogen (Pd-H) interactions lead to phase transitions to palladium hydride (PdHx), compromising sensors' durability and detection speeds after multiple uses. In response, this study introduces a high-performance H2 sensor designed from thiolate-protected Pd nanoclusters (Pd8SR16), which leverages the synergistic effect between the metal and protective ligands to form an intermediate palladium-hydrogen-sulfur (Pd-H-S) state during H2 adsorption. Striking a balance, it preserves Pd-H binding affinity while preventing excessive interaction, thus lowering the energy required for H2 desorption. The dynamic adsorption-dissociation-recombination-desorption process is efficiently and highly reversible with Pd8SR16, ensuring robust and rapid H2 sensing at parts per million (ppm). The Pd8SR16-based sensor demonstrates exceptional stability (50 cycles; 0.11% standard deviation in response), prompt response/recovery (t90 = 0.95 s/6 s), low limit of detection (LoD, 1ppm), and ambient temperature operability, ranking it among the most sensitive Pd-based H2 sensors. Furthermore, a multifunctional prototype demonstrates the practicality of real-world gas sensing using ligand-protected metal nanoclusters.

Development of room-temperature operable TiO2-x-based hydrogen gas sensor with light irradiation

In this research work, TiO2-x-thin films are deposited through a radio-frequency magnetron sputtering technique by varying the oxygen partial pressure (pO2) of 6.0 %, 6.4 %, and 6.8 %. The X-ray diffraction analysis depicts the formation of the anatase phase of the annealed thin film with a high crystalline nature. The existence of higher oxygen vacancies and surface roughness are confirmed by the X-ray photoelectron spectroscopy and the atomic force microscopy analyses, respectively, in the 6.0 % pO2 grown thin film. At room temperature (30 °C) and dark conditions, the optimized TiO2-x-based hydrogen gas sensor device depicts a notable response of 22.9 % on exposure to 100 ppm of H2 gas. The irradiation of the ultra-violet (UV) light (λ = 365 nm) on the sensing material promotes desorption of the oxygen species and hence improves the responsivity of the sample. The highest responsivity of 87.7 %, along with faster response and recovery time of 9.4 s and 7.8 s, respectively, is achieved under the UV light irradiation and 100 ppm of H2 gas for the sample grown at 6.0 % pO2, which signifies its potential for the development of room temperature operable hydrogen gas sensor.

Sensitivity enhancement of hydrogen-gas sensor by sub nm Au on Pd surface of a wireless quartz resonator

Hydrogen (H2) is an important source of next-generation energy production. The various H2 sensors developed to date cannot easily detect very low concentrations of H2 (<10 ppm) at room temperature within 100 s. In this study, we develop H2 sensors by depositing a 200 nm thick palladium (Pd) film on AT-cut quartz resonators and adding a sub nm gold (Au) layer on the Pd surface. Moderate Au deposition on the Pd surface improves the sensitivity of the sensor by decreasing the activation energy of atomic-hydrogen migration from the surface to the subsurface. The optimal Au thickness that minimizes the activation energy is 0.5 nm. Finally, we show that the approximate detection limit at room temperature is 5 ppm.

Rare Earth Material for Hydrogen Gas Sensing: PtGd Alloy Thin Films as a Promising Frontier.

At the focus of our investigation lies the precision fabrication of ultrathin platinum-gadolinium (PtGd) alloy films, with the aim to use these films for resistive hydrogen gas sensing. The imperative for sensitive and selective sensors to harness hydrogen's potential as an alternative energy source drives our work. Applying rare earth materials, we enhance the capabilities of hydrogen gas sensing applications. Our study pioneers PtGd alloy thin films for hydrogen gas sensing, addressing a gap in existing literature. Here, we demonstrate the functional characteristics of 2 nm thick PtxGd100'x (x = 25, 50 and 75) alloy films, analyzing their hydrogen gas sensing properties, comprehensively examining the interplay between alloy composition, temperature fluctuation and hydrogen concentration. The effect of composition and structural properties on the sensing response were assessed using EDX and XPS. The films are tested at a temperature range between 25 °C and 150 °C with hydrogen gas concentrations ranging from 10 ppm to 5%. Hydrogen gas sensing mechanisms in PtGd alloy ultrathin films are explained by surface scattering. The unique combination of Pt and Gd offers promising characteristics for gas sensing applications, including high reactivity with hydrogen gas and tunable sensitivity based on the alloy composition.

Room temperature hydrogen gas sensor based on Pd decorated bridging GaN nanowires

A highly sensitive and low-power consumption hydrogen (H2) gas sensor based on palladium nanoparticles (Pd NPs) decorated bridging GaN nanowires (NWs) has been fabricated, which can be used for H2 detection at room temperature (RT). The bridging GaN NWs growth across the deep trench of GaN coated sapphire substrate were prepared by Metal-organic Chemical Vapor Deposition (MOCVD), and Pd NPs were deposited on the surface of GaN NWs using magnetron sputtering. The characterizations of the structure and morphology of Pd-GaN NWs indicated that the Pd NPs were successfully loaded on the surface of GaN NWs. The sensors with different Pd thickness (2 nm, 5 nm, 10 nm, and 15 nm) were measured at RT (∼ 25 ℃), with H2 concentrations varying from 1 to 10,000 ppm. When the Pd thickness is 10 nm, the H2 response reaches its maximum, has a fast response time (∼3 s toward 10,000 ppm H2) and a low detection limit (LOD) of 42.2 ppb H2. Moreover, the sensor has excellent repeatability, superior H2 selectivity, relatively good humidity-tolerant and long-term stability. In addition, H2 sensing characteristics at different self-heating power (1.9 mW, 6.6 mW, 18.4 mW, and 36.1 mW) were also measured, and found that the H2 response increased with the increase of self-heating power. The fabricated H2 sensor with low-power consumption (without heater or illumination) have a wide application in portable device or Internet of Things (IoT) system.