H2 Sensor Research Articles

Improved hydrogen detection in SnO2-based materials using CuxPd bimetallic catalyst

Hydrogen (H2) holds promise as a replacement for conventional fossil fuels in future energy systems. However, developing a rapid, highly sensitive, and cost-effective H₂ sensor remains a significant challenge. This study first uses a low-cost-oriented CuxPd binary alloy for SnO2 for H2 sensing, and the corresponding properties are evaluated comprehensively. The results of H2 sensitivity demonstrate that our bimetallic CuxPd significantly enhances the sensitivity of SnO2, which is attributed to the synergistic effect of CuxPd bimetallic catalysts Our CuxPd/SnO2 nanocomposite materials not only exhibit high response (401 @ 1000 ppm at 100 °C), rapid response/recovery time (1/12 s @ 1000 ppm at 100 °C) and still maintains good response (1.42) to 1 ppm H2 gas. The introduction of Cu effectively stabilizes Pd and creates more oxygen vacancies, which provides a more catalytic effect than monometallic Pd. Therefore, this work provides a scenario for low-cost catalysis of H2 detection.

Monolayer Amphiphiles Hydrophobicize MoS2-Mediated Real-Time Water Removal for Efficient Waterproof Hydrogen Detection.

Ensuring water-fouling-free operation of semiconductor-based gas sensors is essential to maintaining their accuracy, reliability, and stability across diverse applications. Despite the use of hydrophobic strategies to prevent external water intrusion, addressing in situ-produced water transport during H2 detection remains a challenge. Herein, we construct a novel waterproof H2 sensor by integrating single-atom Ru(III) self-assembly with monolayer amphiphiles embedded in MoS2. The unique monolayer structure enables the sensor to detect H2 in the presence of water, as well as facilitate the self-transport of in situ-generated water from the H2-O2 reaction during H2 detection. Molecular dynamics simulations reveal that monolayer amphiphiles exhibit a higher water diffusion coefficient than multilayer amphiphiles, making them more advantageous for removing in situ-produced water. Deployable on mobile platforms, it enables wireless H2cat detection for up to 6 months, without the introduction of protective membranes against dust and water ingress. This work not only enhances the performance of H2 detection but also introduces a new concept for the advancement of stable water-sensitive sensors.

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.

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.

Observation on Switching Properties of WO3-Based H2 Sensor Regulated by Temperature and Gas Concentration.

Transition metal oxide semiconductors have great potential for use in H2 sensors, but in recent years, the strange phenomena about gas-sensitive performance associated with their special properties have been more widely discussed in research. In some cases, the resistance of transition metal oxide gas sensors will emerge with some changes contrary to their intrinsic semiconductor characteristics, especially in gas sensor research of WO3. Based on the hydrothermal synthesis of WO3, our work focuses on the abnormal change of tungsten oxide resistance to different gases at low temperature (80-200 °C) and high temperature (above 200 °C). Through in situ FT-IR and in situ XPS, combined with density functional theory calculations, a new reasonable explanation of WO3 is proposed for the abnormal resistance change caused by temperature and the strange response due to gas concentration. The occurrence of these findings can be attributed to the synergistic effect resulting from the presence of two contributing factors. One of them is attributed to the alteration in the surface valence state of WO3 induced by gas, resulting in the reduction of W6+. The other one is due to the reaction between gas and adsorbed oxygen on the surface of WO3. This work presents a novel and rational concept for addressing the reaction mechanism between gas and transition metal oxide semiconductors, thereby paving the way for the development of highly efficient gas sensors based on transition metal oxide semiconductors.

Highly Durable Chemoresistive Micropatterned PdAu Hydrogen Sensors: Performance and Mechanism.

Hydrogen (H2) is a promising alternative energy source for Net-zero, but the risk of explosion requires accurate and rapid detection systems. As the use of H2 energy expands, sensors require high performance in a variety of properties. Palladium (Pd) is an attractive material for H2 detection due to its high H2 affinity and catalytic properties. However, poor stability caused by volume changes and reliability due to environmental sensitivity remain obstacles. This study proposes a micropatterned thin film of PdAu with optimized composition (Pd0.62Au0.38) as a chemoresistive sensor to overcome these issues. At room temperature, the sensor has a wide detection range of 0.0002% to 5% and a fast response time of 9.5 s. Significantly, the sensor exhibits excellent durability for repeated operation (>35 h) in 5% H2 and resistance to humidity and carbon monoxide. We also report a negative resistivity change in PdAu, which is opposite to that of Pd. Density functional theory (DFT) calculations were performed to investigate the resistance change. DFT analysis revealed that H2 penetrates specific interstitial sites, causing partial lattice compression. The lattice compression causes a decrease in electrical resistance. This work is expected to contribute to the development of high-performance H2 sensors using Pd-based alloys.

Exploring the influence of Zn impurities on the structural, optical, and H2 sensor properties of ultrasonic spray pyrolysis-grown MgO thin films

Magnesium oxide (MgO) thin films, both pure and zinc (Zn) doped, were fabricated on soda lime glass substrates using ultrasonic spray pyrolysis. Zn was introduced at concentrations of 0.5 %, 1 %, 2 %, 4 %, and 8 %. The effects of these doping levels on the films' structural, morphological, optical, and H2 gas sensing properties were studied using XRD, SEM, EDAX, UV–vis spectroscopy, PL spectroscopy, gas sensing measurements, and XPS. The films showed a cubic crystal structure without secondary phases, and grain sizes generally decreased with doping. Morphological changes in nanocrystal shapes were noted due to impurities. Optimal doping enhanced MgO's absorbance, with a slight increase in bandgap. The PL spectra showed increased luminescent emissions with higher doping, due to defects from Zn ions. Pure films were responsive to H2 gas, while Zn-doped samples showed weaker responses. The XPS confirmed the expected chemical compositions.

Performance enhancement of SAW based hydrogen sensor employing Pd/Ni alloy thin film

Abstract This study focuses on determining the optimized design parameters of palladium/nickel (Pd/Ni) thin film coated surface acoustic wave (SAW) hydrogen (H2) sensors with high sensitivity and fast response by modulating the ratio and thickness of Pd/Ni thin film. The Pd/Ni thin films deposited on the wave propagation path of delay-line patterned SAW sensors had Ni content ranging from 0 to 30 at% and thickness ranging from 20 to 400 nm. A phase discrimination circuit was used to collect the signal of SAW H2 sensor. The experimental results indicated that the response sensitivity of the sensor decreased with the increase of Ni content, while the response time gradually accelerated. Besides, the stability of the sensor deteriorated with increasing thickness, and there existed a non-linear relationship between sensitivity and thickness, and the response time slowed down as the thickness increased. To analyze the SAW sensing mechanism, a theoretical simulation model of the Pd/Ni thin film coated SAW H2 sensor was established using perturbation theory, which was well-validated by experimental results. Considering the requirements of fast response, high sensitivity, and stability of the H2 sensor, the optimal thin film structure parameters were determined as Pd9Ni1 thin film with the thickness of 40 nm.

(Invited) Detection, Location and Quantification of H2 Gas Leaks Based on Data Collected with Electrochemical Sensors in a Specifically Designed Test Chamber

Hydrogen is one of the most important energy gases as it is carbon free and therefore can result in the emission reduction of the greenhouse gas CO2. However, hydrogen itself is a secondary greenhouse gas. As a secondary greenhouse gas, hydrogen does not directly add to global warming by entrapping heat. Instead, it reacts with molecules in the atmosphere that are needed to remove the greenhouse gas CH4. CH4 is comparably short-lived in the atmosphere with approximately 10 years compared to CO2 which can last in the atmosphere for centuries. However, CH4 traps at least 100 times as much heat as CO2. Considering the difference in heat capacities of CH4 and CO2, combined with the difference in lifetime, if the same amount of CH4 and CO2 were to be released into the atmosphere at the same time, the global warming effect of CH4 would be approximately 28 times higher than the warming effect of CO2. This means, by releasing hydrogen in the atmosphere, the global warming effect is indirectly enhanced by increasing the lifetime of CH4. Therefore, it is essential to be able to detect, locate and quantify hydrogen leaks right away.Due to the ever-growing hydrogen infrastructure including production facilities, transportation systems like pipelines, as well as storage facilities and user end stations, it is essential to create low-cost, low-power sensors that can be deployed in high numbers. Electrochemical sensors have the potential to fulfill all the needed criteria and are already used for the detection of hydrogen. However, in order to use these sensors to not only detect the leak, but also to locate and quantify the amount of hydrogen that leaked into the atmosphere, additional models and algorithms are needed. To our knowledge, no system currently exists on the market that can be used to fulfill all three tasks.We built a test chamber that enabled us to evaluate H2 leaks and to collect data with electrochemical sensors in a controlled room and environment. The chamber has the size of 800 x 400 x 450 mm3 with a total volume of 144 L. We placed seven of our commercial electrochemical sensors that can detect 0 – 250 ppm hydrogen at different positions inside the box. The box was equipped with one gas inlet and one gas outlet to ensure pressure stability inside the box during our leak test. The inlet was connected to a gas tube which was connected to two mass flow controllers as well as to an outlet tube via a three-way valve. This way, it could be ensured that the gas stream had a stable volume and a constant speed. We released controlled amounts of hydrogen into the box and collected the data with our seven sensors. We were able to see a location-dependent sensor response over time for a 1 second leak of H2 which indicates the capability of such a sensor system to be used for the location of a leak.Quantifying hydrogen is a very complex issue. It requires extremely accurate readings and an intelligent algorithm that is capable to use the reading from multiple sensors and turn that into a mass of hydrogen leaked or leaking. The extremely accurate reading is difficult because the zero and span readouts from the electrochemical sensor is dependent on temperature as well as humidity. This means that the readout zero and span will have to be compensated for both temperature and humidity. While we currently use algorithms to compensate for temperature, we found that these algorithms are not good enough when the sensors are used to measure concentrations in the low-ppm or ppb range. We are researching AI and other computational means to include both temperature and humidity in the compensation algorithms and how including both variables in the compensation process can improve the sensors performance at low concentrations. Both the H2 sensor and its deployment capabilities are technologically and economically significant to the rapidly expanding H2 market for protecting human health, the environment, stemming expensive product losses and promoting efficient use.

Construction of ultra-sensitive hydrogen sensor based on two phases In2O3 nanoparticles modified by regular dodecahedral ZnO

Hydrogen (H2) is considered one of the promising energy sources to replace fossil fuels so efficient H2 sensing technology is a necessary condition to ensure the safety of people’s livelihood and economic development. In this paper, ZnO obtained by calcination of precursor ZIF-8 has a regular dodecahedral structure. The product of In2O3 obtained with the participation of the surfactant PEO-PPO-PEO has two different crystal forms, namely cubic phase c-In2O3 and hexagonal h-In2O3. Crystal form c-In2O3 is 7.07 wt% of the mass of h-In2O3. When ZnO is 5 wt% of In2O3, the H2 sensor based on the ZnO (5 %)-Inc/Inh composite material has the best response performance and the operating temperature is 450 °C. The sensor’s response time for detecting 5000 ppm H2 is less than 1 s, and the recovery time is 6 s with a response intensity of 79.91. The limit of detection (LOD) is 53 ppb, which is much lower than the explosive concentration (4–75 V/V%). Density functional theory (DFT) is utilized for investigating the performance advantages of Inc/Inh composites over pure c-In2O3 and h-In2O3 and further elaborating the mechanism of ZnO improving the gas-sensing performance of ZnO (5 %)-Inc/Inh. The sensor based on ZnO (5 %)-Inc/Inh composite may guide the research of high-performance H2 sensors. The H2 adsorption mechanism of the sensor was analyzed based on the oxygen adsorption mechanism.

Enhanced Hydrogen Sensing Response Through Controlled Porosity and Diameter of Vertically Aligned ZnO Nanorods

We report phase pure vertically aligned zinc oxide nanorods (ZnO NRs) using a low-cost hydrothermal process on the pre-deposited RF sputtered ZnO seed layer on SiO2/Si substrate. The variation in seed layer thickness is used to control the diameter and surface porosity of ZnO NRs. The average diameter of NRs is ∼ 153, 103, and 90 nm for 2, 4, and 6-min deposited seed layers, respectively, with an average length of ∼ 3 μm irrespective of the seed layer thickness. Further, the Au/Cr interdigitated electrode is deposited on ZnO NRs/SiO2/Si to analyze its H2 sensing performance. It is observed that, among various devices, the 2 min seed layered ZnO NRs (ZNR-2) delivered superior sensing performance with 19.6% relative response, 28 s response, and 104 s recovery time, with exposure to 60 ppm H2 gas at temperature 100 . The limit of detection and limit of quantification for the ZNR-2 device is 68 ppb and 227 ppb, respectively. This device selectively responds to H2 concerning other gases. Thus, the present findings provide the guiding path for improving the sensing response for Zinc oxide-based H2 sensors.

Hollow mesoporous In2O3 derived from MIL-68 (In) for dual gas sensing of NO2 and H2

NO2 is one of the most important air pollutant gases for the environment and human health. H2 is seen as the next generation of clean energy to promote sustainable development. However, sensitive detection of NO2 at room temperature is still a major challenge, and reliable H2 sensors are also scarce. Metal oxide semiconductor (MOS) gas sensors are advantageous for detecting gas. Hence, we synthesized the unique hexahedral hollow mesoporous In2O3 (h-In2O3) derived from MIL-68 (In). The formation process and properties of h-In2O3 were analyzed. The surface of h-In2O3 is rich in hydroxyl groups, which are active sites for NO2 adsorption at room temperature. Increasing working temperature up to 160 °C enables effective sensing reaction with H2. Based on different temperature-dependent gas sensing mechanisms, the h-In2O3 sensor exhibits ultrasensitive response values of 400 towards 100 ppb NO2 at room temperature (24 °C) and of 17.99 towards 10 ppm H2 at 160 °C. In addition, the h-In2O3 sensor exhibits reliable linear response, low theoretical detection limit of 1.8 ppt and 23 ppb for NO2 and H2, excellent selectivity, repeatability and long-term stability. The synergistic effect of the unique structure, larger specific surface area, and abundant adsorbed oxygen plus oxygen vacancy contribute to the excellent gas sensing performance of the h-In2O3 sensor. This study provides a promising strategy for the development of bifunctional 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.

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.

Hydrogen sensing in different hydrogen-carrying gases using composites of PdSnO2 and halloysite nanotubes

In this work, we developed composites of palladium-decorated tin dioxide (PdSnO2) and halloysite nanotubes (HNTs) by adding different amounts of HNTs as additives into PdSnO2, and investigated how the different amounts of HNTs in the composites and the different hydrogen (H2) carrying gases (air and helium (He)) could affect the H2 sensing performance of such composites (PdSnO2-HNT). Through the sensing-performance characterization using H2 carried by air, it was found that PdSnO2 with an appropriate small amount of HNTs (i.e., 2 % of PdSnO2 mass) can improve the sensing performance with respect to limit of detection (LOD) and response/recovery time. Further, the optimal PdSnO2-HNT composite as a sensor was tested to detect H2 in He. The testing results indicated that the composite can detect H2 in He, but its performance parameters (i.e., the profile of calibration curve, LOD, and response time) are different from those of such a sensor in detecting H2 in air. Moreover, the composite still presented better sensing performance than PdSnO2 without HNTs in detecting H2 in He. Possible reasons for the effects of HNT and H2-carrying gas on the sensing performance of PdSnO2-HNT-based sensors were discussed. We believe that this study provides valuable insights into the functionality and the adaptability of PdSnO2-HNT-based H2 sensors in diverse operational conditions.

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.

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.

Rapid photothermal reduction-derived Pt1.6Ni nanoalloys embedded in laser-induced graphene for hydrogen evolution reaction

Water electrolysis is one of the most intriguing technologies for hydrogen production because of its carbon-neutral nature, however the development of efficient electrocatalysts is required to improve the energy conversion efficiency of water splitting. In this study, we suggest a facile route for the fabrication of Pt1.6Ni nanoalloys on laser-induced graphene (Pt1.6Ni NAs/LIG) by the photothermal reduction using commercial CO2 laser which is irradiated on the surface of the LIG. The laser ablation process on the polyimide (PI) film resulted in porous and interconnected graphene sheets, while uniform nanoparticles with an average size of around 4.5 nm were decorated on their surface by the photothermal reduction effect. The overall process took only 60 s. Bonding structure investigation confirmed that PI film was successfully transformed into a graphene structure and the metal precursors were converted into bimetallic nanoalloy by using Raman spectroscopy and XPS, respectively. Electrochemical measurements for hydrogen evolution reaction discovered that the Pt1.6Ni NAs/LIG showed superior catalytic performance which required an overpotential of only 96 mV to achieve a current density of 10 mA cm−2. It exhibited superior catalytic activity compared to LIG (740 mV), Pt NPs/LIG (204 mV), and PtNi1.6 NAs/LIG (205 mV), as well as other previously reported catalysts at the same current density. Based on these results, the Pt1.6Ni NAs/LIG was employed for hydrogen gas collection and detection. The generated bubbles were collected separately from both electrodes, and their compositions with evolution rate were confirmed to be hydrogen using a commercial H2 sensor.

Thermal decomposition and combustion of interior design materials

Research findings on the patterns of thermal decomposition and combustion are reported for widely used interior design materials. The experiments were conducted using a hardware and software system including a thermogravimetric analyzer (to record the characteristics of thermal decomposition), a gas analyzer (with H2, CH4, H2S, SO2, CO and CO2 sensors) and a high-speed camera (to record the characteristics of ignition and combustion). The temperature of the oxidizing medium ranged from 500 to 900°C to investigate the conditions of thermal decomposition initiation and sustained combustion. It was established that the highest concentrations of toxic emissions were typical of the combustion of polypropylene at a maximum temperature of the oxidizing medium (900°C). Wood showed the shortest ignition delay time and the longest duration of combustion. The experimental data were used for a physical problem statement and mathematical model of heat and mass transfer to explore the thermal decomposition and combustion of interior design materials in different rooms. A comparison of the experimental findings with the mathematical modeling results validates the developed model. The growth rates of carbon monoxide and carbon dioxide concentrations were determined for construction (wooden) and interior design (polymer) materials. The maximum concentrations of CO and CO2, and the minimum times taken to reach their threshold values corresponded to wood and polyvinyl chloride panels. This research provides a deeper insight into the thermal decomposition of a wide range of fuels and the formation of gaseous pyrolysis products of these fuels. The results obtained can be used to evaluate the toxicity of construction and interior design materials during compartment fires as well as to estimate the safe egress time and risks involved in the process. They can also serve as a database for the development and testing of mathematical models describing fire outbreaks and propagation in confined spaces.

High performance H2 sensors based on NiO-SnO2 nanosheets in temperature-pulsed operation mode

Enhancements in the responses of semiconductor gas sensors for hydrogen (H2) are imperative to ensure the safety for industrial processes and fuel cells applications. Alternative to the conventional method of maintaining an optimum isothermal temperature, this study presents a novel technique that sequentially modulates the physisorption and chemisorption processes of the target gas and oxygen species through a temperature-pulsed strategy. This method substantially amplified the electrical responses of a NiO-doped SnO2 gas sensor to H2 vapor. Under the optimum pulsed-heating condition, the sensor achieved a remarkable response of 252–300 ppm H2, which is comparable to or better than that of many existing H2 sensors. The integration of a pulse-driven microheater with a heterojunction-forming sensing layer has led to improved sensitivity, providing additional opportunities for H2 monitoring.