Flammability Hazard Research Articles

Climatic Indicators and Their Variation Trends as Conditions for Forest Flammability Hazard in the South of Tyumen Oblast

This study analyzes the forest flammability hazard in the south of Tyumen Oblast (Western Siberia, Russia) and identifies variation patterns in fire areas depending on weather and climate characteristics in 2008–2023. Using correlation analysis, we proved that the area of forest fires is primarily affected by maximum temperature, relative air humidity, and the amount of precipitation, as well as by global climate change associated with an increase in carbon dioxide in the atmosphere and the maximum height of snow cover. As a rule, a year before the period of severe forest fires in the south of Tyumen Oblast, the height of snow cover is insignificant, which leads to insufficient soil moisture in the following spring, less or no time for the vegetation to enter the vegetative phase, and the forest leaf floor remaining dry and easily flammable, which contributes to an increase in the fire area. According to the estimates of the CMIP6 project climate models under the SSP2-4.5 scenario, by the end of the 21st century, a gradual increase in the number of summer temperatures above 35 °C is expected, whereas the extreme SSP5-8.5 scenario forecasts the tripling in the number of such hot days. The forecast shows an increase of fire hazardous conditions in the south of Tyumen Oblast by the late 21st century, which should be taken into account in the territory’s economic development.

Chemical hazard assessment toward safer electrolytes for lithium-ion batteries.

Commercialization of rechargeable lithium-ion (Li-ion) batteries has revolutionized the design of portable electronic devices and is facilitating the current transition to electric vehicles. The technological specifications of Li-ion batteries continue to evolve through the introduction of various high-risk liquid electrolyte chemicals, yet critical evaluation of the physical, environmental, and human health hazards of these substances is lacking. Using the GreenScreen for Safer Chemicals approach, we conducted a chemical hazard assessment (CHA) of 103 electrolyte chemicals categorized into seven chemical groups: salts, carbonates, esters, ethers, sulfoxides-sulfites-sulfones, overcharge protection additives, and flame-retardant additives. To minimize data gaps, we focused on six toxicity and hazard data sources, including three empirical and three nonempirical predictive data sources. Furthermore, we investigated the structural similarities among selected electrolyte chemicals using the ChemMine tool and the simplified molecular input line entry systeminputs from PubChem to evaluate whether chemicals with similar structures exhibit similar toxicity. The results demonstrate that salts, overcharge protection additives, and flame-retardant additives contain the most toxic components in the electrolyte solutions. Furthermore, carbonates, esters, and ethers account for most flammability hazards in Li-ion batteries. This study supports the complementary use of quantitative structure-activity relationship modelsto minimize data gaps and inconsistencies in CHA. Integr Environ Assess Manag 2024;20:2231-2244. © 2024 The Author(s). Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

CFD modelling of methane dispersion from buried pipeline leaks: Experimental validation and hazard distance estimation

The safe operation of buried pipelines necessitates an understanding of potential leak dynamics and the subsequent formation of flammable clouds defining hazard distances. This paper presents a computational fluid dynamics (CFD) model and its validation against experimental data on the dispersion of methane through a sand layer of 100 mm thickness to the atmosphere. A leak orifice diameter of 4 mm was considered for pipeline gauge pressures in the range of 10–300 kPa. This study describes the methane propagation in time through the sand and the development of the flammable cloud in the atmosphere. The simulations demonstrate a high degree of accuracy in capturing the transient behaviour of methane propagation in the sand and dispersion in the atmosphere when compared with a 60 s experiment. The model was applied to predict the development and maximum spread of the flammable cloud and hazard distances are presented. The simulations provide insight into the development of the flammable cloud. The validated CFD model can serve as a predictive tool for hazard distance estimation in case of buried leaks, inform safer pipeline design and improve emergency response strategies for gas leaks.

Ungulates mitigate the effects of drought and shrub encroachment on the fire hazard of Mediterranean oak woodlands.

Climate change is increasing the frequency of droughts and the risk of severe wildfires, which can interact with shrub encroachment and browsing by wild ungulates. Wild ungulate populations are expanding due, among other factors, to favorable habitat changes resulting from land abandonment or land-use changes. Understanding how ungulate browsing interacts with drought to affect woody plant mortality, plant flammability, and fire hazard is especially relevant in the context of climate change and increasing frequency of wildfires. The aim of this study is to explore the combined effects of cumulative drought, shrub encroachment, and ungulate browsing on the fire hazard of Mediterranean oak woodlands in Portugal. In a long-term (18 years) ungulate fencing exclusion experiment that simulated land abandonment and management neglect, we investigated the population dynamics of the native shrub Cistus ladanifer, which naturally dominates the understory of woodlands and is browsed by ungulates, comparing areas with (no fencing) and without (fencing) wild ungulate browsing. We also modeled fire behavior in browsed and unbrowsed plots considering drought and nondrought scenarios. Specifically, we estimated C. ladanifer population density, biomass, and fuel load characteristics, which were used to model fire behavior in drought and nondrought scenarios. Overall, drought increased the proportion of dead C. ladanifer shrub individuals, which was higher in the browsed plots. Drought decreased the ratio of live to dead shrub plant material, increased total fuel loading, shrub stand flammability, and the modeled fire parameters, that is, rate of surface fire spread, fireline intensity, and flame length. However, total fuel load and fire hazard were lower in browsed than unbrowsed plots, both in drought and nondrought scenarios. Browsing also decreased the population density of living shrubs, halting shrub encroachment. Our study provides long-term experimental evidence showing the role of wild ungulates in mitigating drought effects on fire hazard in shrub-encroached Mediterranean oak woodlands. Our results also emphasize that the long-term effects of land abandonment can interact with climate change drivers, affecting wildfire hazard. This is particularly relevant given the increasing incidence of land abandonment.

RGO/In2O3 heterostructures based gas sensor for efficient ppb-level n-butanol detection

The real-time and effective detection of n-butanol gas is particularly important in production and daily life due to its flammability, toxicity, and potential hazards to the environment. This article reports the preparation of hollow indium oxide spheres and rGO/In2O3 composites through a simple hydrothermal and subsequent heat treatment method. Test results indicate that the gas sensitivity of n-butanol can be significantly improved through rGO composites. The prepared hollow indium oxide spheres are composed of nanosheets with a diameter of probably 500 nm. After combination by rGO, the specific surface area and the proportion of adsorbed oxygen of the material are increased, both of which are advantageous for enhancing gas sensitivity abilities. At the optimum operating temperature of 160 °C, the response value of rGO/In2O3 complex sensor is 51–50 ppm of n-butanol, which is 3.6 times the response of pure In2O3. Gas sensors composed of rGO/In2O3 exhibit ultra-fast response time and low detection limit. Even for ppb grade (100 ppb) n-butanol gas, the response value is still 2.3. These characteristics make rGO/In2O3 a promising material for the preparation of high-performance n-butanol gas sensors. Besides, the gas-sensitive mechanism of the enhanced n-butanol sensing performances is also analyzed.

PREDICTING THE FLARE TEMPERATURE OF BINARY FUEL

A method for calculating the flash point from the results of simulating liquid–solid equilibrium at constant pressure using the Gibbs equation is discussed. A model is used to predict the flash point of the mixture based on the modified Le Chatelier equation, the Antoine equation and a model for estimating the activity coefficient. The flammability hazard of liquids is primarily characterized by their flash point. The flash point is defined as the temperature at which a liquid evaporates and forms a flammable mixture with air. To measure the flash point, closed and open type devices are used. In closed-type devices, the state of equilibrium between the liquid and vapor components of the mixture is studied. Open type devices take into account the interaction of a mixture of flammable liquids with the atmosphere. The flash point of a mixture is a critical property, but experimental data for many mixtures are lacking and obtaining such data is expensive and time-consuming. Therefore, the development of mathematical models for analyzing the state of the environment under conditions of increasing risk of emergency situations is an important scientific and practical task. This paper examines the possibility of predicting the flash point in closed-type devices, i.e. the influence of atmospheric conditions is not taken into account in this approximation. Several models for predicting the flash point for mixtures of various types have been proposed previously. Keywords: binary mixtures, flash point, boiling point, activity coefficients, solvation coefficient, association coefficient.

Spatial distribution of wildfire threat in the far north: exposure assessment in boreal communities

Increased wildfire activity has raised concerns among communities about how to assess and prepare for this threat. There is a need for wildfire hazard assessment approaches that capture local variability to inform decisions, produce results understood by the public, and are updatable in a timely manner. We modified an existing approach to assess decadal wildfire hazards based primarily on ember dispersal and wildfire proximity, referencing landscape changes from 1984 through 2014. Our modifications created a categorical flammability hazard scheme, rather than dichotomous, and integrated wildfire exposure results across spatial scales. We used remote sensed land cover from four historical decadal points to create flammability hazard and wildfire exposure maps for three arctic communities (Anchorage and Fairbanks, Alaska and Whitehorse, Yukon). Within the Fairbanks study area, we compared 2014 flammability hazard, wildfire exposure, and FlamMap burn probabilities among burned (2014–2023) and unburned areas. Unlike burn probabilities, there were significantly higher in exposure values among burned and unburned locations (Wilcoxon; p < 0.001) and exposure rose as flammability hazard classes increased (Kruskal–Wallis; p < 0.001). Very high flammability hazard class supported 75% of burned areas and burns tended to occur in areas with 60% exposure or greater. Areas with high exposure values are more prone to burn and thus desirable for mitigation actions. By working with wildfire practitioners and communities, we created a tool that rapidly assesses wildfire hazards and is easily modified to help identify and prioritize mitigation activities.

Demonstrating on-demand production of bio-ethylene oxide in a two-step dehydration-epoxidation process with chemical looping operations

Ethylene oxide (EO) is a key chemical intermediate produced almost exclusively from petrochemically derived ethylene. Currently, EO manufacturing involves epoxidation of ethylene with O2 over Ag/Al2O3 - one of the highest CO2-emitting processes in the chemical sector (Boulamanti and Moya, 2017). The flammability hazards associated with incumbent methods and sluggish process start-ups prevent small-scale, flexible operations or alignment with intermittently available renewable resources. Presented herein is a novel process for on-demand production of bio-EO from bioethanol. Ethanol, laboratory-grade or denatured, was first dehydrated to ethylene over HZSM-5 (at 280 °C) or γ-Al2O3 (at 350 °C) catalysts, producing ethylene and water. The ethylene stream was then selectively oxidised to EO over Ag/SrFeO3 at 270 °C using lattice oxygen from a solid – SrFeO3, employed to drive chemical looping epoxidation (CLE). For a configuration where the dehydration and epoxidation reactions were carried out in separate reactors, the process produced EO with 57 % selectivity at 15 % conversion of ethylene, thus exceeding the incumbent approach with pure Ag/α-Al2O3 and O2. In an alternative configuration, experiments were carried out in one dehydration-epoxidation reactor layered with two catalysts: HZSM-5 and Ag/SrFeO3. The results revealed that water presence at a percentage level enhanced unselective combustion. In-situ removal of water, possible with an additional layer of a drying material between the two catalysts, proved effective in boosting the process performance, reaching selectivity to EO of 50 % at 12 % conversion of ethylene. The catalysts showed no sign of deactivation when using denatured ethanol or when performing experiments intermittently. Hence, our novel process can be kept offline without penalty, allowing for on demand production and complete alignment with renewable resources.

The limiting oxygen volume fraction for opposed flame spread extinction

The limiting oxygen volume fraction (LOC) for flame spread is a parameter used to determine flammability and fire hazard. The LOC depends on the solid material, geometry, and environmental conditions. It is important to understand the relationship between these conditions and the LOC, particularly for environments different than Earth atmospheres. Future spacecraft will have sub-atmospheric cabin pressures designed to reduce preparation time for extravehicular activities. This work attempts to provide further information on this aspect of solid fuel flammability by conducting experiments to determine the effect of ambient pressure and external radiant flux for flames spreading downward over cylindrical samples of black polymethyl methacrylate (PMMA). The experimental methodology is based on test methods ASTM 2863 (LOI) and ASTM E-1321 (LIFT), that are used to determine some aspects of material flammability, specifically extinction and flame spread under external radiant heating. Experiments are conducted in a pressure chamber at pressures from 40 to 100 kPa with radiant heating from 0 to 3.3 kW/m2. Results show that decreasing either the ambient pressure or the external radiant flux increases the LOC of the PMMA. The results are correlated in terms of the ratio of the partial pressure of oxygen, radiant flux, and ambient pressure with an equation that includes the LOC at atmospheric pressure. It is found that the heat transfer and chemical kinetic mechanisms that control the flame spread are primarily dependent on the oxygen molar fraction, explaining the experimental observations. The data from this work will be compared with experiments to be conducted in the International Space Station (ISS) under the SoFIE-MIST project to provide further understanding of the effect spacecraft environments have on the LOC of materials. The results will give further insight into the flammability of materials, particularly at sub-atmospheric ambient pressures found in spacecraft, aircraft, and high-altitude locations.

Analysis and prediction of hydrogen-blended natural gas diffusion from various pipeline leakage sources based on CFD and ANN approach

The influences of pipeline leakage source types on the hazard area distribution caused by accidental hydrogen-blended natural gas leakage are still the focus of gas leakage accidents. Three types of pipeline leakage sources are discussed in this study. Namely, the gas in the vertical pipeline flows from top to bottom, and the leakage orifice is in the pipeline wall; the gas in the vertical pipeline flows from bottom to top, and the leakage orifice is in the pipeline wall; the leakage orifice is in the horizontal pipeline end. The common feature of the above three pipeline leakage sources is that the normal of leakage orifice is parallel to the horizontal plane. The differences in the flow field distribution of hydrogen-blended natural gas released from three pipeline leakage sources are compared through numerical simulation. The effect of various factors on the jet centerline, concentration decay, and maximum horizontal diffusion distance of hydrogen-blended natural gas released from three pipeline leakage sources are analyzed. The predictive models of hydrogen-blended natural gas's maximum horizontal diffusion distance in three pipeline leakage sources under multi-factor coupling are established through a backward propagation neural network (BPNN). Results show that the angle between the gas flow direction in the pipeline and the normal of the leakage orifice, and the background step flow cause differences in the concentration field near the leakage orifice from the three pipeline leakage sources at the same working conditions. In the near-field region, the leakage orifice diameter has the most significant influence on the jet centerline of three hydrogen-blended natural gas jets among three factors. The concentration decay rate of gas released from the horizontal pipeline end is greater than that of gas released from the other two pipeline leakage sources. With the increase of volumetric flow rate, the maximum horizontal diffusion distances of methane released from three pipeline leakage sources all increase, while the maximum horizontal diffusion distances of hydrogen released from three pipeline leakage sources have little change. The predictive models of the maximum horizontal diffusion distance of hydrogen-blended natural gas released from three pipeline leakage sources are established through BPNN. The maximum horizontal hazard distances of the new working conditions are predicted, and the predicted results are in good agreement with the numerical simulation results. This investigation has guiding value for fast and accurate prediction of flammable gas hazard areas.

Research progress of organic liquid electrolyte for sodium ion battery.

Electrochemical energy storage technology has attracted widespread attention due to its low cost and high energy efficiency in recent years. Among the electrochemical energy storage technologies, sodium ion batteries have been widely focused due to the advantages of abundant sodium resources, low price and similar properties to lithium. In the basic structure of sodium ion battery, the electrolyte determines the electrochemical window and electrochemical performance of the battery, controls the properties of the electrode/electrolyte interface, and affects the safety of sodium ion batteries. Organic liquid electrolytes are widely used because of their low viscosity, high dielectric constant, and compatibility with common cathodes and anodes. However, there are problems such as low oxidation potential, high flammability and safety hazards. Therefore, the development of novel, low-cost, high-performance organic liquid electrolytes is essential for the commercial application of sodium ion batteries. In this paper, the basic requirements and main classifications of organic liquid electrolytes for sodium ion batteries have been introduced. The current research status of organic liquid electrolytes for sodium ion batteries has been highlighted, including compatibility with various types of electrodes and electrochemical properties such as multiplicative performance and cycling performance of electrode materials in electrolytes. The composition, formation mechanism and regulation strategies of interfacial films have been explained. Finally, the development trends of sodium ion battery electrolytes in terms of compatibility with materials, safety and stable interfacial film formation are pointed out in the future.

Toward the future of firefighter gear: Assessing fluorinated and non-fluorinated outer shells following simulated on-the-job exposures.

In 2022, the occupation of firefighting was categorized as a "Group 1" carcinogen, meaning it is known to be carcinogenic to humans. The personal protective equipment that structural firefighters wear is designed to safeguard them from thermal, physical, and chemical hazards while maintaining thermo-physiological comfort. Typically, the outer layer of structural turnout gear is finished with a durable water and oil-repellent (DWR) based on per- and polyfluoroalkyl substances (PFAS) that helps limit exposure to water and hazardous liquids. The PFAS-based aqueous emulsion typically used in DWR finishes is highly persistent and can cause various health problems if absorbed into the body through ingestion, inhalation, and/or dermal absorption. In response, the U.S. Fire Service has begun using non-PFAS water repellants in firefighter turnout gear. This study aims to evaluate the performance of both traditional PFAS-based and alternative non-PFAS outer shell materials. The study involved exposing both PFAS-based and non-PFAS DWR outer shell materials in turnout composites to simulated job exposures (i.e., weathering, thermal exposure, and laundering) that artificially aged the materials. After exposures, samples were evaluated for repellency, durability, thermal protection, and surface chemistry analysis to determine any potential performance trade-offs that may exist. Non-PFAS outer shell fabrics were found not to be diesel/oil-repellent, posing a potential flammability hazard if exposed to diesel and subsequent flame on an emergency response. Both PFAS-based and non-PFAS sets of fabrics performed similarly in terms of thermal protective performance, tearing strength, and water repellency. The surface analysis suggests that both PFAS and non-PFAS chemistries can degrade and shed from fabrics during the aging process. The study indicates that firefighters should be educated and trained regarding the potential performance trade-offs, such as oil absorption and flammability concerns when transitioning to non-PFAS outer shell materials.

Effect of additional side shielding on the wire arc additive manufacturing of AZ31 magnesium alloy

Magnesium (Mg) alloys have a low density among the structural metals, but it is hard to be plastically deformed due to their crystallographic nature. Wire arc additive manufacturing (WAAM) could be one of the alternative processes to fabricate the Mg products for various industrial applications. Nonetheless, it is used in limited industrial fields due to challenging issues such as low commercial availability of wire, high oxygen affinity, explosive and flammable hazard, and typical defects of WAAM like distortion and side collapse, grain coarsening, etc. In this research, it was tried to find out the better way to fabricate the WAAM of AZ31 alloy. An additional Ar gas side shielding was given during the WAAM process, and compared with the conventional shielding method. It was observed that the global shielding affects the microstructural evolution of the WAAM product, and influences the mechanical property in a positive way.

Assessing genuine flammability hazard of halogenated species for their safe processing and use: Case studies

It is recognized that the combustion of halogenated substances (gas and liquids) may present specific features compared to traditional hydrocarbons. As a matter of facts, the standardized flammability characterization methods referenced by the various regulations (transport, labeling, etc.) do not necessarily take the specific features of these substances into account. Subsequently, this may lead to an underestimation of the risk associated with their use (physical hazard such as explosion). Through two case studies of interest, one concerning a fluorinated liquid, the other focusing on a fluorinated gas, this work reveals technical difficulties that may arise in appraising actual flammability hazards of halogenated hydrocarbons, due to their combustion specific behavior, when applying existing flammability methods without appropriate expert judgement. In the case of the liquid ethoxy-nonafluorobutane (Novec 7200™) this work highlights that this substance can be erroneously considered non-flammable due a clear pitfall of flash point methods, whilst its genuine flammability can be revealed otherwise. Regarding gaseous halogenated species, we show that operating conditions shall be carefully selected to reveal the genuine flammability behavior of such substances. Indeed, this is not necessarily correctly identified in all possible flammability hazard rating standard methods. In this study, the application of European standards allows to confirm that R1234ze(E) is flammable at temperatures below 30 °C, at atmospheric pressure and at a humidity of 50%RH.

Comparison of hydrogen and hydrocarbon fuels hazards and practical risk management strategies

AbstractThe use of hydrogen as a fuel and energy carrier is increasing globally. Existing processes are being expanded, and hydrogen is also being incorporated into novel technologies and processes. As new hydrogen applications and processes are being developed, it is important for industry professionals to understand the associated hazards and how they differ from the hazards of hydrocarbon fuels. While best practices and risk management strategies for hydrocarbon fuel processes are mature and generally known within thre industry, the hazards of hydrogen processes, such as liquid storage tanks and fuel dispensers, are less commonly understood by those who may be planning to enter this industry. The objective of this paper is to explain the hazards of hydrogen and to provide a comparison of these hazards with those of commonly used hydrocarbon fuels through a review of the flammable hazards, consequence modeling, and select hydrogen‐release incidents. The analysis will provide current industry risk practitioners with useful guidance to understand the hazards associated with this increasingly popular fuel. This paper provides information in three main sections. The first section provides a review and comparison of fire and explosion hazards for hydrogen as compared to hydrocarbon fuels. Second section provides consequence modeling results comparing hydrogen and hydrocarbon fuels for similar release scenarios using a common software model (DNV Phast version 8.71). Third section provides a review of select hydrogen incidents.

Trinity flame retardant with benzimidazole structure towards unsaturated polyester possessing high thermal stability, fire-safety and smoke suppression with in-depth insight into the smoke suppression mechanism

Although possessing polymer with excellent flame retardant and low heat release have emerged in previous work, synchronously suppressing smoke (fatal hazards in fire disasters) is still a dilemma. Adjusting the key intermediate-polycyclic aromatic hydrocarbons (PAHs) during the burning processes is a promising path to achieve low smoke release. In this work, we constructed the benzimidazole structure, as an aromatization precursor to chemically modify ammonium polyphosphate (APP) to obtain a trinity flame retardant (APP-BIM). Unsaturated polyester resin (UP), as a typical polymer with high flammability and smoke hazards being the research model, exhibit excellent thermal stability and fire safety compared with previous work. Meanwhile, a homemade smoke sampling module (SSM) coupling with a cone calorimeter (Cone-SSM) is also constructed for online acquiring the soot particles during burning for in-depth investigation of smoke suppression mechanism. This strategy provides a promising new approach to effectively reduce the fire hazard of polymers.

Consequence modeling of liquefied petroleum gas accidental release from retail outlets in an African city residential environment

AbstractThe drive by the Nigerian government to increase the usage of liquefied petroleum gas (LPG) within the country has led to the rapid growth of refill stations without adherence to international safety and regulatory guidelines on gas handling. This has increased associated hazards such as explosions and fires leading to loss of life and damage to properties. This study employed the Areal Locations of Hazardous Atmospheres software to model the consequences of explosion and fire due to accidental leakage of LPG into the environment in four selected locations in the Ilorin metropolis under four scenarios. The longest threat zones were observed in Scenario II in all the selected refill stations. The flammability hazard for gas station 1 was predicted to be 98 and 238 m for the red and yellow threat zones, respectively. For thermal radiation, the predicted threat zones are 17, 27, and 43 m for 10, 5, and 2 kW/m2, respectively. January was observed to have the longest threat zones, particularly in the flammability hazard which indicates the influence of atmospheric weather conditions on dispersion. To reduce the accidental release of LPG, continuous enlightenment on safety rules is mandatory for all.

Qualitative Inherent Safety Assessment for Flammability Evaluation of Deep Eutectic Solvent

Due to the increasing demand for green and sustainable analytical methods, many researchers have been using various attempts to improve and design environmentally friendly chemical processes. Based on the literature, most of the researchers agreed that DESs is one of the attractive solutions to environmentally friendly chemicals due to its classification as a green solvent and safe to use due to its low flammability characteristic. Although studies on the benefits and advantageous implementation of DESs are extensive, investigation on the safety level of DESs is still lacking. This paper aims to introduce a simple qualitative inherent safety assessment method for flammability evaluation of DESs. Flash point values of the HBA and HBD component of DES are used in evaluating the flammability level of the DES. Subjective score assignment was utilized based on the flash point data as well as mixing temperature in the production of DES. In this scoring method, higher score represents higher flammability hazard. The resulted scoring method has five level of hazards representing five range of flash point values with 5 indicates the highest and most hazardous score while 1 is the lowest and the least hazardous score. Implementation on a simple case study shows that this scoring method is easy to use and can be easily improved for future usage as more safety information on DES emerge.

Transient hydrogen crossover in dynamically operated PEM water electrolysis cells - A model-based analysis

Hydrogen crossover in polymer electrolyte membrane electrolysis cells is important concerning faradaic efficiency, flammability hazards, and degradation phenomena. In recent years, steady-state H2-in-O2 measurements have demonstrated that the hydrogen crossover increases with current density, due to mass transport limitations in the cathode catalyst layer. However, hydrogen crossover during dynamic operation has not been investigated yet. Therefore, this study investigates the hydrogen crossover with a dynamic macroscopic 1-D through-plane model of a polymer electrolyte membrane electrolysis cell. The model focuses on the detailed description of the dynamics of the reactions and mass transport of hydrogen in the membrane electrode assembly. Simulated down steps in current density, lead to transient overshoots in the H2-in-O2 content at the anode side. The membrane acts as short-term mass storage for the dissolved hydrogen, and mass transport lags the instant response of the current density. Under specific conditions with high cathode mass transport limitations, the lower explosion limit of H2-in-O2 can be transiently exceeded. This work provides for the first-time insights into transient hydrogen crossover phenomena and is a further step into dynamic model-based analysis of polymer electrolyte water electrolysis cells.

Phosphonate-Functionalized Ionic Liquid Gel Polymer Electrolyte with High Safety for Dendrite-Free Lithium Metal Batteries.

The conventional lithium-ion battery technology relies on the liquid carbonate-based electrolyte solution, which causes excessive side reactions, serious risk of electrolyte leakage, high flammability, and significant safety hazards. In this work, phosphonate-functionalized imidazolium ionic liquid (PFIL) is synthesized and used as a gel polymer electrolyte (GPE) to replace the organic carbonate-based electrolyte solution. The as-prepared ionic liquid-based gel polymer electrolyte (IL-GPE) shows low crystallinity, flame retardance, and excellent electrochemical performance. Thanks to the fast double channel transport of lithium ions in the IL-GPE electrolyte, a high ionic conductivity of 0.48 mS cm-1 and a lithium-ion transference number of 0.37 are exhibited. Symmetrical lithium cells with IL-GPE retain stable cycling even after 3000 h under 0.1 mA cm-2. IL-GPE exhibits good compatibility toward lithium metal, yielding excellent long-term electrochemical kinetic stability. IL-GPE induces the formation of a uniform and robust SEI layer, inhibiting the growth of lithium dendrites and improving the rate performance and cycle stability. Furthermore, Li/LiFePO4 cells exhibit a specific capacity of 63 mA h g-1 after 150 cycles at 5.0 C, with a capacity retention of 90.2%. It is foreseen that this GPE is a promising candidate to enhance the safety of high-performance lithium metal batteries.