H2 Gas Sensor Research Articles

Review on progress in synthesis of CdS‐based composites and their potential applications

AbstractIn recent times, there has been a growing interest among materials communities in functional nanomaterials. This paper aims to explore the fundamental advancements in the role of Cadmium sulfide (CdS) in photoelectrochemical water splitting, CO2 conversion, photocatalytic H2 conversion, photovoltaic devices, and gas sensors. Additionally, we provide a summary of key points and propose avenues for advancing research on CdS‐based composites.

Sol-Gel Pt-VO2 Films as Selective Chemoresistive and Optical H2 Gas Sensors.

In this work, VO2 (M1/R) thin films were exploited as H2 gas sensors. A flat film morphology, obtained by furnace annealing, was compared with a laser-induced nanostructured one. The combination of the environmentally friendly sol-gel approach with the ultrafast laser crystallization allows for significant reductions in energy consumption and related emissions during the fabrication of VO2 sensors. By decorating the sensors' surface with Pt nanoparticles (NPs), the sensor response was enhanced exploiting the hydrogen spillover effect. The Pt/VO2 sensors, tested at operating temperatures between 20 and 200 °C and for concentration of H2 from few ppm to 50000 ppm, offered a dual chemoresistive and optical sensing mode. Low operating temperatures of 150 °C were achieved, along with a detection limit as low as 2 ppm and a perfect baseline recovery. Both sensors guaranteed specific selectivity toward H2, without response to NO2 or humidity, and long-term stability over 500 h. The H2 sensing mechanism, for both the monoclinic and rutile VO2 phases, was investigated through in operando X-ray Diffraction and in situ X-ray Photoelectron Spectroscopy tests. The interaction was found to be based on the reversible formation of HxVO2 bronze, along with the reversible variations in the oxidation state of V.

Long-term reliable wireless H2 gas sensor via repeatable thermal refreshing of palladium nanowire

The increasing significance of hydrogen (H2) gas as a clean energy source has prompted the development of high-performance H2 gas sensors. Palladium (Pd)-based sensors, with their advantages of selectivity, scalability, and cost-effectiveness, have shown promise in this regard. However, the long-term stability and reliability of Pd-based sensors remain a challenge. This study not only identifies the exact cause for performance degradation in palladium (Pd) nanowire H2 sensors, but also implements and optimizes a cost-effective recovery method. The results from density functional theory (DFT) calculations and material analysis confirm the presence of C = O bonds, indicating performance degradation due to carbon dioxide (CO2) accumulation on the Pd surface. Based on the molecular behavior calculation in high temperatures, we optimized the thermal treatment method of 200 °C for 10 minutes to remove the C = O contaminants, resulting in nearly 100% recovery of the sensor’s initial performance even after 2 months of contamination.

Experimental and theoretical studies of sputter deposited pure SnO2 thin films for high selective and humidity-tolerant H2 gas sensor

Experimental and theoretical studies of sputter deposited pure SnO2 thin films for high selective and humidity-tolerant H2 gas sensor

Uniform Nanocrystal Spatial Distribution-Enhanced SnO2-based Sensor for High-Sensitivity Hydrogen Detection.

Hydrogen (H2) is colorless, odorless, and has a wide explosive concentration range (4-75 vol %), making rapid and accurate detection of hydrogen leaks essential. This paper demonstrates a method to modify the spatial distribution of nanocrystals (NCs) by adding surfactants to improve the sensing performance. In order to explore its potential for H2 gas-sensing applications, SnO2, containing different mass percentages of PdCu NCs, was dispersed. The results show that the 0.1 wt % PdCu-SnO2 sensor based on surfactant dispersion performs well, with a response to 0.1 vol % H2 that is 18 times higher than that of the undispersed 0.1 wt % PdCu-SnO2 sensor. The enhanced gas-sensing ability after dispersion can be attributed to the fact that the uniform distribution of NCs generates higher quantum efficiency and exposes more active sites on the carrier surface compared to nonuniform distribution. This study provides a simple, novel, and effective method to improve the sensor response.

Flexible hybrid nanostructured chemiresistive sensing platform for low-temperature trace hydrogen detection

The prevalence of hydrogen (H2) utilization across commercial and industrial sectors has spurred the innovation of various H2 gas sensors. However, their practical implementation has been hindered by issues such as cost inefficiency, low sensitivity, inadequate selectivity, and limitations in low-temperature sensing capabilities. Consequently, the development of a sensor capable of surmounting these challenges is paramount for widespread adoption. In this study, a cost-effective approach has been used to fabricate a flexible hybrid nanostructured platform on polyethylene terephthalate (PET) substrate incorporating a combination of zinc oxide (ZnO), titanium oxide (TiO2), and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). This platform has undergone meticulous morphological characterization and comprehensive evaluation for H2 gas sensing applications at both room temperature and 50˚C. The results reveal that the developed PEDOT:PSS/TiO2/ZnO NWs sensor exhibits superior H2 gas sensing characteristics with 141 % and 163 % higher response by proportions at 100 ppb and 100 ppm, respectively outperforming other prepared devices in the same environment. Thus demonstrating exceptional sensitivity of 0.448 %/ppm with three cycle repeatability, H2 selectivity and nine months of stability at low temperatures. Moreover, the sensor has an ultralow limit of detection (LOD) of ∼9 ppt, along with a rapid response time of 65 s and a recovery time of 42 s at an H2 concentration of 100 ppb. This research drives the advancement of efficient, rapid-responsive, and discerning trace detection of H2 gas at low temperatures.

Fabrication of PANI/GO/Pd nanocomposite based tapered optical fiber for hydrogen gas sensing applications

Hydrogen (H2) is viewed as a promising solution for future energy demands because of its effectiveness, widespread availability, environmentally friendly properties, and sustainability. The study focuses on developing and evaluating H2 gas sensors based on optical fiber coated with nanocomposites such as polyaniline (PANI), graphene oxide (GO), and palladium (Pd) as sensing layers. An optical transducing channel was developed using a 125 μm diameter multimode optical fiber to improve the light field. The optical fiber was reduced to 20 μm and coated with the PANI/GO/Pd nanocomposite using drop casting. The proposed optical fiber sensor achieved a sensitivity of 9.79/vol%. The response and recovery time were calculated at room temperature and found to be 60 and 190 s, respectively. Overall, the developed optical fiber sensor shows high stability and excellent selectivity to H2 gas when compare to other gases such as NH3 and CH4.

Ppb-level H2 gas-sensor based on porous Ni-MOF derived NiO@CuO nanoflowers for superior sensing performance

Nickel oxide (NiO) is an optimal material for precise detection of hydrogen (H2) gas due to its high catalytic activity and low resistivity. However, the solid structure of NiO imposes limitations on the gas response kinetics of H2 gas molecules, resulting in a slower electron–hole transit and reduced gas response value. Herein, a unique NiO@CuO NFs with porous sharp-tip and nanospheres morphology was successfully synthesized by using a metal–organic framework (MOF) as a precursor. The fabricated porous 2 wt% NiO@CuO NFs describes outstanding selectivity towards H2 gas, including a high sensitivity of response value (170–20 ppm at 150 °C), is almost 28.3 % higher than that of porous Ni-MOF, low detection limit (300 ppb) with a notable response (21), short response and recovery times at (300 ppb, 40/63 s and 20 ppm, 100/167 s), exceptional long-term stability and repeatability. The study also explored the impact of relative humidity to evaluate the sensor performance under real-world conditions. The boosted hydrogen dioxide sensing properties may be attributed to synergistic effects of numerous factors including p-p heterojunction at the interface between NiO and CuO nanoflowers, especially a porous sharp-tip MOF structure and rough surface of nanospheres as well as the chemical sensitization effect of NiO. This research offers a viable method for creating unique MOS heterostructures from Ni-MOF and CuO that have unique morphologies and compositions that could be used for H2 gas sensing applications.

Spontaneously decorated palladium nanoparticles on redox active covalent organic framework for chemiresistive hydrogen gas sensing

A rapid hydrogen (H2) sensor operating at room temperature is fabricated using covalent organic framework (COF), namely Pyromellitic dianhydride and tris(4-aminophenyl)amine (PMDA-TAPA), PT COF that has a unique ability to spontaneously reduce Pd2+ into Pd0 nanoparticles without the aid of external reducing agents. The presence of surface redox sites in COF enable the rapid formation of Pd nanoparticles on COF surface under ambient conditions. The generated material, hitherto named as Pd@amicPT portrayed remarkable H2 sensing characteristics with a rare combination of high response % (67.3 ± 1) and rapid response/recovery times (5.3/3.5 s, respectively) for 1 % H2 under ambient conditions. Our results demonstrated appreciable reproducibility, repeatability, and long term stability of sensor that remained unaffected by relative humidity and a high selectivity towards H2. Further, sensor performance is found to be superior when compared to many Pd loaded 2D material based chemiresistive H2 gas sensors.

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.

Highly stable and selective H2 gas sensors based on light-activated a-IGZO thin films with ZIF-8 selective membranes

Metal-organic frameworks (MOFs) have emerged as promising selective membranes in oxide semiconductor gas sensors. However, their susceptibility to high temperatures poses significant challenges to the long-term stability of gas sensors. This paper proposes a novel approach for improving long-term stability by employing a light-activated technique on amorphous InGaZnO (a-IGZO) films with a ZIF-8 membrane. Under 360 nm LED illumination, UV light can penetrate the ZIF membrane and be absorbed by a-IGZO, leading to a substantial number of photogenerated carriers in the IGZO film for gas reaction. The a-IGZO film with a ZIF-8 membrane shows an excellent selective response for H2 over CO, NO2, and O3. This light-activated film maintains a gas response comparable to that of thermal-activated counterparts while significantly improving its long-term stability. Our findings underscore the potential of light-activated a-IGZO sensors as a platform for future integration with an MOF selective membrane, ensuring long-term stability.

Nanotransistor-based gas sensing with record-high sensitivity enabled by electron trapping effect in nanoparticles

Highly sensitive, low-power, and chip-scale H2 gas sensors are of great interest to both academia and industry. Field-effect transistors (FETs) functionalized with Pd nanoparticles (PdNPs) have recently emerged as promising candidates for such H2 sensors. However, their sensitivity is limited by weak capacitive coupling between PdNPs and the FET channel. Herein we report a nanoscale FET gas sensor, where electrons can tunnel between the channel and PdNPs and thus equilibrate them. Gas reaction with PdNPs perturbs the equilibrium, and therefore triggers electron transfer between the channel and PdNPs via trapping or de-trapping with the PdNPs to form a new balance. This direct communication between the gas reaction and the channel enables the most efficient signal transduction. Record-high responses to 1–1000 ppm H2 at room temperature with detection limit in the low ppb regime and ultra-low power consumption of ~\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document}300 nW are demonstrated. The same mechanism could potentially be used for ultrasensitive detection of other gases. Our results present a supersensitive FET gas sensor based on electron trapping effect in nanoparticles.

Maximized nanojunctions in Pd/SnO2 nanoparticles for ultrasensitive and rapid H2 detection

H2 energy has gained massive attraction as a promising candidate for future energy sources. However, the explosive properties of H2 arouse significant safety concerns, emphasizing the need for the development of real-time H2 detection systems. This study presents the fabrication of an ultrasensitive and selective H2 gas sensor using Pd/SnO2 nanoparticles (NPs) synthesized through the utilization of Pluronic F-127. Pluronic F-127 improves the dispersion and regulates the particle size of Pd NPs. Pd/SnO2 NPs, which are comprised of numerous nanojunctions, exhibit H2 response of 27,190 and a response time of 3 s when exposed to 50 ppm of H2 at 100 °C. The practical applicability of Pd/SnO2 NPs was demonstrated by detecting H2 generated from water-splitting cells, exhibiting promising features for H2 energy industries. Overall, the synthetic method of this study proposes advanced strategies for development of sensing materials with maximized gas sensing performance.

Selective Detection of H2 Gas in Gas Mixtures Using NiO‐Shelled Pd‐Decorated ZnO Nanowires

AbstractHydrogen (H2) gas is a green fuel, but its leakage during storage and transportation can lead to disasters due to its explosive nature. Here, a sensitive and selective H2 gas sensor is developed that can detect H2 in H2/CO and H2/NO2 gas mixtures. First, ZnO nanowires (NWs) are grown using vapor–liquid–solid growth. This is followed by atomic layer deposition‐mediated growth of Pd nanoparticles (NPs) on the ZnO NWs and uniform deposition of a thin NiO shell layer (12 nm in thickness) over the Pd‐decorated ZnO NWs. Characterization of the synthesized samples by different methods confirms the desired chemical composition, morphology, and phases. H2 gas sensing studies reveals the highly sensitive and selective response of the optimized gas sensor to H2 at 200 °C. In the presence of H2/CO and H2/NO2 gas mixtures, the NiO‐shelled Pd‐decorated ZnO NW sensor displays good selectivity for H2, but not the Pd‐decorated ZnO NW gas one. The NiO‐shelled Pd‐decorated ZnO NW gas sensor efficiently detected H2 also in the presence of 40% relative humidity and displays good stability even after 1 month. The present results can open the doors to the fabrication of highly selective H2 gas sensors using the described rationale design.

Design of Pentacene Thin-Film Transistor Based Hydrogen Gas Sensor with High-K Dielectric Materials for High Sensitivity

Electrical properties of an organic field-effect transistor were modelled in top gate top contact (TGTC) geometry and H2 gas sensors were designed for increased sensitivity based on the structure. Safety concerns related to hydrogen usage must be addressed; these hazardous characteristics include a wide flammable range (4%–75%) that results in a rapid burning velocity, a low minimum ignition energy (0.017 mJ), a high heat of combustion (143 kJ g−1), and the high diffusivity of hydrogen gas (0.61 cm2 s−1 in the air). These characteristics make it impossible to control hydrogen combustion after a specific time. All simulations were performed in the Silvaco TCAD ATLAS tool. We analysed the driving principle of gas sensors and introduced gas sensing properties in OFET using platinum metal at the gate electrode for H2 gas detection. IOFF, ION, and VTH are sensitivity parameters that alter when the metalwork function of the gate changes with respect to the gas present on it. The designed sensor was analysed for different dielectric materials. Results demonstrate that the increase in sensitivity for OFET-based H2 sensors is 73.4%, 80.7%, 90.5%, and 95.6% when the work function changes by 50, 100, 150, and 200 meV for Pt gate electrodes with an increase in dielectric value of insulating layer from SiO2 (3.9) to La2O3 (27). Results were compared with the In1-xGaxAs CGNWFET-based H2 sensor as the work function varies at 200 meV,the sensitivity enhancement with OFET-based H2 sensors is 8.09%.

Potential high-performance H[formula omitted] gas sensors based on monolayer 2D metal oxide [formula omitted]-MoO[formula omitted] doped with Pt/Rh[formula omitted]predicted by DFT calculations

High-performance H2 gas sensors based on monolayer 2D metal oxide α-MoO3 doped with Pt/Rh has been predicted. With a binding energy of −5.262 eV/−5.877 eV, the substitutional doping of Pt/Rh for Mo is a stable doping. After adsorbing O2 in air, the band gap of Pt/Rh-α-MoO3 decreases by 0.62 eV/0.51 eV due to the appearance of the impurity levels and the band narrowing effect. Due to such large decrease, electrons in the valence band can be excited more easily into the conduction band to produce more O2(ads)−, which would oxidize more H2 to generate H2O or hydroxyl along with releasing more electrons to the sensor and increasing the sensor’s sensitivity. First losing electrons through adsorbing O2 molecules in air and then obtaining electrons through adsorbing H2 molecules in H2, the charge variation of the sensor based on monolayer Pt/Rh-α-MoO3 is 1.487 e/0.394 e for per O2/H2, which suggests that the sensor may have higher sensitivity and lower detection limit. The larger charge variation is also confirmed by the shift of the Fermi level towards the higher energy direction after adsorbing H2.

Optimization of Deposition Parameters of SnO2 Particles on Tubular Alumina Substrate for H2 Gas Sensing

Resistive gas sensors, which are widely used for the detection of various toxic gases and vapors, can be fabricated in planar and tubular configurations by the deposition of a semiconducting sensing layer over an insulating substrate. However, their deposition parameters are not often optimized to obtain the highest sensing results. Here, we have investigated the effect of deposition variables on the H2 gas sensing performance of commercially available SnO2 particles on tubular alumina substrate. Utilizing a tubular alumina substrate equipped with gold electrodes, we varied the number of deposited layers, rotational speed of the substrate, and number of rotations of the substrate on the output of the deposited sensor in terms of response to H2 gas. Additionally, the effect of annealing temperatures (400, 500, 600, and 700 °C for 1 h) was investigated. According to our findings, the optimal conditions for sensor fabrication to achieve the best performance were the application of one layer of the sensing material on the sensor with ten rotations and a rotation speed of 7 rpm. In addition, annealing at a lower temperature (400 °C) resulted in better sensor performance. The optimized sensor displayed a high response of ~12 to 500 ppm at 300 °C. This study demonstrates the importance of optimization of deposition parameters on tubular substrates to achieve the best gas sensing performance, which should be considered when preparing gas sensors.

A proof of concept for reliability aware analysis of junctionless negative capacitance FinFET-based hydrogen sensor

This work demonstrates the reliability-aware analysis of the Junctionless negative capacitance (NC) FinFET employed as a hydrogen (H2) gas sensor. Gate stacking of the ferroelectric (FE) layer induces internal voltage amplification owing to the NC property, thus, improving the sensitivity of the baseline junctionless FinFET. A well-calibrated TCAD model is used to investigate the sensing characteristics of the proposed FinFET-based H2 sensor by employing the palladium (Pd) metallic gate as a sensing element. The mechanism involves the transduction of H2 gas molecules over the metal gate; due to the diffusion process, some atomic hydrogen diffuses into the metal. The H2 gas absorption at the metal surface causes a dipole layer formation at the gate and oxide interface, which changes the metal gate work function. As a result, this change in the work function can be used as a sensing parameter of the proposed gas sensor. Further, the threshold voltage and other electrical characteristics, such as output conductance, transconductance, and drain current are examined for sensitivity analysis for both NC and without NC JL FinFET at different pressure ranges, keeping the temperature constant (i.e. 300 K). The device variation, i.e. Fin thickness, Fin height, doping and thickness of HfO2 ferroelectric layer, etc, on sensor sensitivity has been evaluated through extensive simulation. This paper also presents a detailed investigation of the sensor’s reliability in terms of work function variation, random dopant fluctuation, trap charges, and device aging, i.e. end of a lifetime. At last, the acquired results are compared with earlier reported data, which justifies the profound significance of the proposed junctionless negative capacitance FinFET-based H2 gas sensor.

High-performance hydrogen gas sensor system based on transparent coaxial cylinder capacitive electrodes and a volumetric analysis technique

A high-performance H2 gas sensor system based on capacitive electrodes and a volumetric analysis technique were developed. Coaxial capacitive electrodes were fabricated by placing a thin copper rod in the center and by adhering a transparent conductive film on the exterior surface of a graduated cylinder. Thus, H2 from a polymer specimen lowered the water level in the cylinder between the two electrodes, producing measurable changes in capacitance that allowed for the measurement of the H2 concentration emitted from the specimen enriched by H2 under high-pressure conditions. The sensing system detected diffused/permeated hydrogen gas from a specimen and hydrogen gas leaks caused by imperfect sealing. The hydrogen gas sensor responded almost instantly at 1 s and measured hydrogen concentrations ranging from 0.15 to 1500 ppm with controllable sensitivity and a measurable range. In addition, performance tests with polymer specimens used in hydrogen infrastructure verified that the sensor system was reliable; additionally, it had a broad measurement range to four decimal places. The sensor system developed in this study could be applied to detect and characterize pure gases (He, N2, O2 and Ar) by real time measurement.

Catalytic Metal‐Gated Nano‐Sheet Field Effect Transistor and Nano‐Sheet Tunnel Field Effect Transistor Based Hydrogen Gas Sensor‐ A Design Perspective

AbstractIn this work, for the first time, the catalytic metal gate (CMG) based nanosheet Field Effect Transistor (NSFET) and nanosheet Tunnel Field Effect Transistor (NSTFET) are proposed for nano‐scale device dimensions, and the different design aspects of catalytic metal gate (CMG)‐based transduction for Hydrogen (H2) sensing are extensively investigated using numerical device simulation. The influence of applied biasing conditions and structural parameter specifications on the sensing performance of CMG‐NSFET and CMG‐NSTFET are methodically analyzed from device electrostatics and carrier transport mechanisms. Furthermore, the relative maximum sensitivity variations with H2‐partial pressure, ambient temperature, and the presence of ambient Oxygen are comprehensively studied. The study reveals that compared to CMG‐NSFET, the CMG‐NSTFET demonstrates a high immunity against bias and doping variations, with a notably higher (> 50%) sensitivity within low H2 partial pressures (10−15 – 10−10 Torr). Next, the sensing performance of CMG‐NSTFET is systematically optimized through a band‐gap and gate‐stack engineering approach, leading to a 180% to 650% sensitivity improvement from lower (10−15 Torr) to higher (10−5 Torr) range of H2 partial pressure. Finally, the performance of optimized CMG‐NSFET and CMG‐NSTFET are extensively benchmarked against other reported nanostructured CMG‐FET and TFET‐based H2 gas sensors, exhibiting a notably higher sensitivity in the proposed sensors.