Subzero Conditions Research Articles

An Ultralow Temperature Aqueous Battery with Proton Chemistry

AbstractConventional aqueous batteries usually suffer from serious capacity loss under subzero conditions owing to the freeze of electrolytes. To realize the utilization of aqueous batteries in extremely cold climates, low‐temperature aqueous battery systems have to be developed. Herein, an aqueous Pb‐quinone battery based on p‐chloranil/reduced graphene oxide (PCHL‐rGO) in H2SO4 electrolyte is developed. Such aqueous Pb/PCHL‐rGO batteries display H+ insertion chemistry, which endows the batteries with fast reaction kinetics and high rate capability. In addition, the hydrogen bonds between water molecules can be significantly damaged in electrolyte by modulating the interaction between SO42− and water molecules, lowering the freezing point of electrolyte. As a result, the Pb/PCHL‐rGO batteries deliver extraordinary electrochemical performance even at −70 °C. This work will broaden the horizons of aqueous batteries and open up new opportunities to construct low‐temperature aqueous batteries.

Designing Self-Sustainable Icephobic Layer by Introducing a Lubricating Un-Freezable Water Hydrogel from Sodium Polyacrylate on the Polyolefin Surface

A convenient, environment-friendly, and cost-effective method to keep anti-icing for a long time was highly desirable. Slippery lubricant layers were regarded to be effective and promising for anti-icing on different surfaces, but the drought-out of lubricants and the possible detriments to the environment were inevitable. By combining super-high molecular weight sodium polyacrylate (H-PAAS) with polyolefin through a one-pot method, a self-sustainable lubricating layer with extremely low ice adhesion of un-freezable water hydrogel was achieved at subzero conditions. The lubricant hydrogel layer could auto-spread and cover the surface of polyolefin after encountering supercooled water, frost, or ice. Due to the reduction of storage modulus in the interface, the ice adhesion of the specimen surfaces was far below 20 kPa, varying from 5.13 kPa to 18.95 kPa. Furthermore, the surfaces could preserve the fairly low adhesion after icing/de-icing cycles for over 15 times and thus exhibited sustainable durability. More importantly, this method could be introducing to various polymers and is of great promise for practical applications.

Mutual diffusion of proteins in cold concentration gradients measured by holographic interferometry

Protein mutual diffusion in cold concentration gradients is important for development of processes involving biopharmaceutical formulations. The diffusivities of α-chymotrypsinogen (aCgn), ovalbumin (Ova) and IgG1 were measured from −10 °C to 25 °C, by holographic interferometry at protein concentrations ranging from 5 g/L to 31.5 g/L in multicomponent systems containing sucrose (up to 10% mass). A dialysis step enabled to measure mutual diffusion of the proteins under equi-chemical potential conditions of the other components. The protein could therefore be considered a single component in a continuous fluid, as defined by Stokes-Einstein (SE) assumption. Overall, the SE model provided a reasonable description for mutual diffusion of all the proteins studied, with higher accuracy for aCgn and IgG1 in the full range of temperatures and concentrations. Ova with 10% sucrose, was less accurately described by this model, diffusing 20% faster than predicted. It was also observed a non-linear temperature dependence for the diffusion of Ova in a 10% sucrose medium: this was only apparent at a temperature near −10 °C. The Williams Landel Ferry (WLF) model was used to provide a measure of the non-Arrhenius regime taken the glass transition temperature (Tg) of the mixture Ova+ sucrose as reference (WLF constants obtained are C1,g ~ 18 and C2,g ~ 1). Overall, the present work offers a new approach to obtain experimental diffusion coefficients of relevant protein formulations under sub-zero conditions. The accuracy of classical transport models was explored in this manuscript which can help to gather insight into transport properties of globulins and Mabs under concentration polarization gradients occurring during freezing: deviations to the linear diffusion-temperature relation above Tg – i.e., “continuous medium” diffusion predicted by SE model - can be quantified by the WLF model. Diffusion coefficients may be further related with protein conformational changes and this was proposed for Ova.

The Influence of Sub-Zero Conditions on the Mechanical Properties of Polylactide-Based Composites.

Polylactide-based composites filled with waste fillers due to their sustainability are a subject of many current papers, in which their structural, mechanical, and thermal properties are evaluated. However, few studies focus on their behavior in low temperatures. In this paper, dynamic and quasi-static mechanical properties of polylactide-based composites filled with 10 wt% of linseed cake (a by-product of mechanical oil extraction from linseed) were evaluated at room temperature and at −40 °C by means of dynamic mechanical analysis (DMA), Charpy’s impact strength test and uniaxial tensile test. It was found that the effect of plasticization provided by the oil contained in the filler at room temperature is significantly reduced in sub-zero conditions due to solidification of the oil around −18 °C, as it was shown by differential scanning calorimetry (DSC) and DMA, but the overall mechanical performance of the polylactide-based composites was sufficient to enable their use in low-temperature applications.

Antifreeze Proteins and Their Practical Utilization in Industry, Medicine, and Agriculture.

Antifreeze proteins (AFPs) are specific proteins, glycopeptides, and peptides made by different organisms to allow cells to survive in sub-zero conditions. AFPs function by reducing the water’s freezing point and avoiding ice crystals’ growth in the frozen stage. Their capability in modifying ice growth leads to the stabilization of ice crystals within a given temperature range and the inhibition of ice recrystallization that decreases the drip loss during thawing. This review presents the potential applications of AFPs from different sources and types. AFPs can be found in diverse sources such as fish, yeast, plants, bacteria, and insects. Various sources reveal different α-helices and β-sheets structures. Recently, analysis of AFPs has been conducted through bioinformatics tools to analyze their functions within proper time. AFPs can be used widely in various aspects of application and have significant industrial functions, encompassing the enhancement of foods’ freezing and liquefying properties, protection of frost plants, enhancement of ice cream’s texture, cryosurgery, and cryopreservation of cells and tissues. In conclusion, these applications and physical properties of AFPs can be further explored to meet other industrial players. Designing the peptide-based AFP can also be done to subsequently improve its function.

The influence of amylose and amylopectin on water retention capacity and texture properties of frozen-thawed konjac glucomannan gel

As freeze-thaw processing has become an emerging way to regulate the texture properties of the konjac glucomannan (KGM), the freezing-induced syneresis is getting increased concern in the food industry. In this study, the effects of the different types' starches (amylose and amylopectin) and the frozen conditions on the water retention capacity and texture properties of the frozen KGM-Starch blended gel (KS gel) were investigated. Comparing the effects of the subzero conditions and the starches on the blended gel, we found that the latter would be more powerful to affect the syneresis rate and water holding capacity of the frozen KGM gel, and a dense porous network microstructure emerged in the frozen KS gels. Research results also showed that the water holding capacity of the frozen KS gels could be significantly improved for the increased starches content, while their syneresis rate could be lowered significantly (p < 0.05). Besides, the KGM-amylose blended gel showed a greater value of hardness and chewiness than that of the KGM-amylopectin blended gel after being subjected to the same frozen condition. While even though no significant difference in the SR could be observed between the KGM blended gels treated with the different frozen conditions (frozen time, subzero temperature, and the number of freeze-thaw cycles), a noticeable change in their texture properties could still be detected. What's more, results showed that starch types and concentrations would profoundly affect the proportion of water at different states in the KGM blended gels. These results suggest that the frozen-thawed stability of the KGM gel could be improved by adding in the different types of starch, which may provide some guidance for the production of frozen KGM gel food.

In situ cloud ground-based measurements in the Finnish sub-Arctic: intercomparison of three cloud spectrometer setups

Abstract. Continuous, semi-long-term, ground-based in situ cloud measurements were conducted during the Pallas Cloud Experiment (PaCE) in 2013. The measurements were carried out in Finnish sub-Arctic region at Sammaltunturi station (67∘58′ N, 24∘07′ E; 560 m a.s.l.), part of Pallas Atmosphere – Ecosystem Supersite and Global Atmosphere Watch (GAW) program. The main motivation of the campaign was to conduct in situ cloud measurements with three different cloud spectrometer probes and perform an evaluation of their ground-based setups. Therefore, we mutually compared the performance of the cloud and aerosol spectrometer (CAS), the cloud droplet probe (CDP) and the forward-scattering spectrometer probe (FSSP-100) (DMT; Boulder, CO, USA). We investigated how different meteorological parameters affect each instrument's ground-based setup operation and quantified possible biases and discrepancies of different microphysical cloud properties. Based on the obtained results we suggested limitations for further use of the instrument setups in campaigns where the focus is on investigating aerosol–cloud interactions. Measurements in this study were made by instruments owned by the Finnish Meteorological Institute and results concern their operation in sub-Arctic conditions with frequently occurring supercooled clouds. The measured parameter from each instrument was the size distribution, and additionally we derived the number concentration, the effective diameter, the median volume diameter and the liquid water content. A complete intercomparison between the CAS probe and the FSSP-100 ground setups and additionally between the FSSP-100 and the CDP probe ground setups was made and presented. Unfortunately, there was not a sufficient amount of common data to compare all three probes together due to operational problems of the CDP ground setup in sub-zero conditions. The CAS probe that was fixed to one direction lost a significant number of cloud droplets when the wind direction was out of wind iso-axial conditions in comparison with the FSSP-100 and the CDP, which were both placed on a rotating platform. We revealed that CAS and FSSP-100 had good agreement in deriving sizing parameters (effective diameter and median volume diameter from 5 to 35 µm) even though CAS was losing a significant amount of cloud droplets. The most sensitive derived parameter was liquid water content, which was strongly connected to the wind direction and temperature.

A review on the degradation of properties under the influence of liquid medium of hybrid polymer composites

Hybrid polymer composites are more attractive because of their light in weight, more robust and rigid (in the direction of fiber) than traditional or unreinforced polymers with the added advantage of having their design and form adapted to suit the specifications of a particular application by the combination of the right choice of the materials. Reinforcement in a polymer hybrid composite can be fiber, filler, or fiber& filler together. Integrating reinforcement into polymers can lead to significant growth in the wear characteristics and mechanical properties of the polymer. Nevertheless, in applications wherever interaction by the liquid medium is inevitable, the mechanical properties and wear characteristics of hybrid polymer composites undergo degradation, which is a generally seen phenomenon since liquid medium acts as a plasticizer. This study aims to provide detailed information on the mechanical and tribological effects of hybrid polymer composites. More emphasis is given towards degradation of mechanical properties such as tensile strength, bending strength, and degradation of wear characteristics like erosion wear rate, and respective failure characteristics were analyzed under different environments such as water, kerosene, saline, sub-zero conditions.

Delay of ice formation on penguin feathers

Cold-weather penguins continually dive in and out of the water and get splashed by waves during the frigid Antarctic winter. Yet, even under these extreme sub-zero conditions, macroscopic ice crystals are typically not observed on their feathers. In this work, we hypothesize that the origin of the anti-icing properties of a cold-weather penguin’s feathers comes from a unique combination of the feather’s macroscopic structure, the nanoscale topography of its barbules, and the hydrophobicity of its preen oil. We show that, the combination of all three, make cold-weather penguin feathers both highly water repellant and icephobic. In this paper, we present the results from a series of droplet freezing experiments performed on feathers from a number of species of both cold-weather and warm-weather penguins. Compared to a smooth glass substrate, freezing was delayed by a factor of 30-times for drops deposited on warm-weather penguin feathers and 60-times for cold-weather penguins. The difference in freezing time between warm- and cold-weather penguins was statistically significant and can be attributed to the increase in the contact angle measured between the drop and the feather of the cold-weather penguin. This increased contact angle is the result of an increase in the hydrophobicity of the preen oil and the inclusion of nanoscale, air-trapping dimples on the surface of the barbules. The physics of this delay are explained through the development of a simple heat transfer model which demonstrates that increasing contact angle is a primary cause of increased freezing time and icephobicity. The results of this study can be used to motivate the designs of biomimetic surfaces to minimize ice formation in extreme conditions for a number of important engineering applications.

Hydrogels as Durable Anti-Icing Coatings Inhibit and Delay Ice Nucleation

The accumulation of ice on surfaces brings dangerous and costly problems to our daily life. Thus, it would be desirable to design anti-icing coatings for various surfaces. We report a durable anti-icing coating based on mussel-inspired chemistry, which is enabled via fabricating a liquid water layer, achieved by modifying solid substrates with the highly water absorbing property of sodium alginate. Dopamine, the main component of the mussel adhesive protein, is introduced to anchor the sodium alginate in order to render the coating applicable to all types of solid surfaces. Simultaneously, it serves as the cross-linking agent for sodium alginate; thus, the cross-linking degree of the coatings could be easily varied. The non-freezable and freezable water in the coatings with different cross-link degrees all remain liquid-like at subzero conditions and synergistically fulfill the aim of decreasing the temperature of ice nucleation. These anti-icing coatings display excellent stability even under harsh conditions. Furthermore, these coatings can be applied to almost all types of solid surfaces and have great promise in practical applications.

Investigation of mechanical vibration effect on proton exchange membrane fuel cell cold start

A three-axis vibration platform is first constructed and utilized in the investigation of the effects of mechanical vibration on the cold start performance of a proton exchange membrane (PEM) fuel cell. In addition, an intermittent pattern of purging is adopted to improve the purging efficiency. The applied vibrations are found to promote water dispersion, but ultimately do not enhance water removal. Under subzero conditions (−13 °C), the vibration of the fuel cell improves cold start performance via delayed freezing, especially when vibrating at the fuel cell natural frequency (10 Hz). With an increase in vibration amplitude, the freezing rate is found to be slow and eventually plateau. Finally, the vibration in the vertical axis is found to play a positive role in improving cold start performance; the effects of other orientations depend on the startup temperature. The result of cold start under vibration might indirectly prove the existence of super-cooled water.

A Comparative Study of Sulfate-Based Neutral pH Polymer Electrolytes: Effects of Temperature on Ionic Conductivity

The ion-conducting properties of two neutral pH polymer electrolytes using polyacrylamide (PAM) with Li2SO4 or Na2SO4 ion conductors were studied and compared at various temperatures. Their electrochemical performance over temperatures was correlated to the respective thermal characteristics. Ion hopping was considered as the likely mechanism for both electrolytes at and above ambient temperatures, determined by their low activation energies for conduction. At elevated temperatures where both electrolytes contained fully solvated ions, the ionic conductivity was highly dependent on the mobility of its hydrated ions. While Na2SO4-PAM showed higher ionic conductivity than Li2SO4-PAM at elevated temperatures, the trend was reversed under sub-zero conditions. Cells with Li2SO4-PAM electrolyte maintained good capacitive behavior at −30 °C, whereas the cells with Na2SO4-PAM had a catastrophic loss of capacitance at low temperatures. The low temperature phenomenon was correlated to the formation of crystal hydrate with different amount of crystallized water, which affected the hopping sites for ion conduction differently. This understanding will provide insights for materials and operating conditions selections in the next generations of aqueous-based polymer electrolytes.

ICE CRYSTAL DYNAMICS IN THE NANOCOMPOSITE NETWORKS

Water is abundant in every day's life and critically useful in many biological systems and in water-based mechanical devices. Freeze-thaw process is one of the inevitable dynamics especially for the materials working at sub-zero conditions where ice crystal changes the physical property of the whole crystal-embedded composite systems. However, still many phenomena have not been explained in terms of crystal control methodology in conjunction with mechanical properties. In this study, ice crystal dynamics occurring in network systems has been discussed. Small size of network structure contributes to crystal growth inhibition especially time-dependent recrystallization. This could be explained by nano-scale confinement effect at the initial nucleation/growth stage, controlling size and shape of ice crystallites. The physical property of crystal embedded-nanocomposite is dominated by ice crystal behaviors over the network. This includes freezing point depression, frequency-dependent and temperature-dependent storage modulus changes and cooling rate- dependent dynamics. This study sheds light on ice crystal control methodology which would be useful in various materials and machines working under freeze-thaw dynamics.

Non-toxic printed supercapacitors operating in sub-zero conditions

Aqueous supercapacitors offer a safe alternative for intermediate energy storage in energy harvesting applications, but their performance is limited to relatively warm temperatures. We report the performance of glycerol as a non-toxic anti-freeze for a water-based electrolyte from room temperature to −30 °C at various concentrations. The supercapacitors are manufactured with graphite and activated carbon as current collector and electrode on a flexible polyester (PET) substrate by stencil printing, with a sodium chloride solution as the electrolyte. The devices are characterized at various constant temperatures for electrical performance, as well as in room temperature for mass loss and development of performance over time. It is shown that supercapacitors with glycerol function well in the decreased temperatures compared to water: the capacitance experiences only a slight decrease and the leakage current is significantly reduced. The equivalent series resistance is affected the most by the reduced temperatures, and should be considered the primary limiting factor in low-temperature applications. Electrolytes with 30–40% glycerol perform the best in commercial freezer temperatures, but below −20 °C a higher concentration of 45% glycerol retains better function. The results show great promise for a non-toxic alternative for improving the temperature range of printed supercapacitors.

The effects of winter stress on Sphagnum species with contrasting macro- and microdistributions

ABSTRACTIntroduction. Sphagnum L. forms much of the ground cover in northern peatlands. Different species show affinities for bioclimatic regions in Europe (oceanic/continental; northern/southern) and species-specific tolerance of winter conditions can be a factor explaining their distribution.Methods. We focussed on low temperature in a series of experiments and tested (1) the innate ability of a selection of Sphagnum species to tolerate low temperature in relation to their micro-topographic (wetness) and geographical (climate) distribution; (2) the rate of cold tolerance acquisition; and (3) the ability of species to survive a range of low temperature once cold hardened.Key results. Our experiments showed that maximal PSII efficiency (Fv/Fm, chlorophyll fluorescence), growth rates and survival were all negatively affected by sub-zero temperatures. Environmental conditions associated with the onset of winter (colder nights and shorter days) triggered the acquisition of cold tolerance in Sphagnum.Conclusions. The results were not unequivocal, but species associated with colder climates were generally more tolerant of sub-zero conditions. Species associated with the wettest and driest ends of the wetness gradient were more consistent in their responses than those in between, with wetter-dwelling species being less sensitive to sub-zero temperature than species found in drier microhabitats. Overall, our results suggest that adaptation to winter conditions contribute to the current distribution patterns of Sphagnum species.

Climate change and rapid ice melt: Suggestions from abrupt permafrost degradation and ice melting in an alpine ice cave

Among the different elements of the mountain cryosphere, ice caves still represent the lesser known part of it. Here we present a seven-year-long record of air and rock temperature in a cave of the southeastern European Alps. We demonstrate how the presence of a permanent ice deposit in the cave is not only related to the net cooling effect of the air circulation, as it is well known, but also to the occurrence of relict permafrost. Through a detailed representation of temperature patterns inside the cave, both air and rock data show how after a period of perennially subzero (cryotic) conditions in the rock, ongoing anthropogenic climate warming is responsible for permafrost degradation despite the cooling effect of the air circulation in the cave. Data support the important role of cryotic conditions in the rock in preserving a permanent ice cave deposit in the present climate, even once the possible relict permafrost inherited from the past disappears. A thickness of 29–44 m of permafrost, possibly formed during the Little Ice Age, has now almost completely disappeared. The present abrupt ice degradation observed in this cave is further exacerbated by positive feedbacks related to warmer air circulation in the cave system.

Direct Driven Hydraulic Drive: Effect of Oil on Efficiency in Sub-Zero Conditions

Direct driven hydraulic drives (DDH) have the advantages of compact high power density in hydraulic systems and flexible control of electric motors. These advantages can benefit non-road mobile machinery (NRMM) applications. However, maintaining high efficiency while working in sub-zero conditions with NRMM is challenging. Therefore, this paper investigates the effect of hydraulic oil on the efficiency of a DDH in a cold environment for an NRMM application. In the DDH setup, the speed and position control of a double-acting cylinder was implemented directly with an electric motor drive in a closed-loop system without the conventional control valves. Efficiency measurements of the DDH setup with two oils (conventional multi-grade and high-performance) were conducted under different operating conditions (speed and payload) and environmental conditions (temperature in °C). The paper provides an evaluation of the electro-hydraulic system and a discussion on the usage of hydraulic oil by non-road mobile working machines in sub-zero conditions. An experimental investigation demonstrated an improvement in efficiency of 5%-unit at 22 °C, from 2%-unit to 5%-unit at 3 °C, and of almost a 10%-unit at temperatures below zero (−10 °C) by changing oil.

Cryoprotectant role of exopolysaccharide of Pseudomonas sp. ID1 in the vitrification of IVM cow oocytes.

Biological molecules isolated from organisms that live under subzero conditions could be used to protect oocytes from cryoinjuries suffered during cryopreservation. This study examined the cryoprotectant role of exopolysaccharides of Pseudomonas sp. ID1 (EPS ID1) in the vitrification of prepubertal and adult cow oocytes. IVM oocytes were vitrified and warmed in media supplemented with 0, 1, 10, 100 or 1000µgmL-1 EPS ID1. After warming, oocytes were fertilised and embryo development, spindle morphology and the expression of several genes in Day 8 blastocysts were assessed. Vitrification led to significantly lower proportion of prepubertal oocytes exhibiting a normal spindle configuration. In fresh control oocytes and most groups of vitrified adult oocytes, similar percentages of oocytes with a normal spindle configuration were observed. Percentages of Day 8 blastocysts were similar for prepubertal oocytes vitrified in the absence or presence of 1 or 10µgmL-1 EPS ID1 and for adult oocytes vitrified in the presence of 10µgmL-1 EPS ID1 compared with non-vitrified oocytes. EPS ID1 supplementation had no effect on solute carrier family 2 member 3 (SLC2A3), ubiquitin-conjugating enzyme E2A (UBE2A) and histone deacetylase 1 (HDAC1) expression in Day 8 blastocysts form adult oocytes. However, supplementation with 10 and 100µgmL-1 EPS ID1 led to increased expression of genes involved in epigenetic modifications (DNA methyltransferase 3 alpha (DNMT3A) and K (lysine) acetyltransferase 2A (KAT2A)) and apoptosis (BCL2 associated X apoptosis regulator (BAX) and BCL2-like 1 (BCL2L1)). The lowest BAX:BCL2L1 ratio was found in the 10µgmL-1 EPS ID1-supplemented group. The results suggest that 10µgmL-1 EPS ID1 added to vitrification and warming media may help protect bovine oocytes against cryodamage.

Design approach of a density-driven solar water heater system

Energy conservation continues to play a crucial role in social and economic development. With the remarkable increase in oil prices and exploring solutions for the replacement of fossil fuels, an ecofriendly energy resource has become the priority among more and more people. Keeping the intension for reducing the global warming impact and looking for alternative clean source of energy, solar energy applications such as solar thermal systems, solar water heating and cooling are becoming energy-efficient designs. One of the widely used applications of solar energy is solar water heating systems. Low-cost solar water heaters can cover the domestic needs for water in the range of 100–200 l per day. Solar water heating systems are generally more efficient and advantageous in hot areas. However, the application of solar water heating is still a challenge in winter and sub-zero conditions, having low solar irradiance. In such conditions, solar water heating system cannot produce enough energy, which drives a need for evaluating system component design and improves its performance during low ambient conditions. In this study, detailed design methods for solar water heater components are discussed for cold regions like North Dakota, USA. The type of system chosen in this study is natural circulation-based solar water heating system. The study will also compare the experimental data with previously conducted numerical analysis.

Sub-Zero Cell Reversal Tolerance in Polymer Electrolyte Membrane Fuel Cells

Polymer electrolyte membrane fuel cells (PEMFCs) have gained considerable attention in recent years for application in electric vehicles, portable devices, and cogeneration systems. Large scale commercialization of PEMFCs mainly requires addressing the high cost issues associated with the fuel cell stack in addition to the challenges associated in building H2 infrastructure. Though, significant amount of research has been carried out in developing low Pt loaded Membrane Electrode Assemblies to meet the 2020 DOE performance targets for automotive applications, there are still challenges associated in meeting durability requirements due to catalyst layer and membrane degradation. It is well documented voltage cycling during start-up/shutdown process leads to Pt dissolution and loss of electrochemical surface area of Pt and thereby affecting the durability. Fuel cells stacks need to be robust against both specific and non-specific failure modes. Specific failure modes of MEA can be predicted by operating conditions/parameters, however non-specific failure mode such as cell reversal is difficult to predict. Though, system level mitigation can be employed to minimize the impact of cell reversal, there is a potential cost trade-off associated with this approach. Ballard1 was first to develop and report the impact of cell reversal tolerance above sub-zero conditions with and without cell reversal tolerance catalyst in the MEA. Cell reversals2 can occur mainly during reactant starvation and especially during H2 starvation under freeze start-up operation. This presentation will focus on evaluating the impact of operating parameters on cell reversal under sub-zero conditions and will highlight the mechanism and potential ways to improve cell reversal tolerance under sub-zero conditions. Figure 1 shows the impact of current density on cell reversal tolerance under sub-zero conditions3. As it can be seen, significant reduction in sub-zero reversal tolerance noticed with current density. To the best of our knowledge, we evaluated for the first time, the cell reversal tolerance under sub-zero conditions. References S.D.Knights, D.P.Wilkinson, S.A. Cambell, J.L.Taylor, J.M. Gascoyne and T.R. Ralph, Solid polymer fuel cell with improved voltage reversal tolerance. US Patent 6936370.C. Qin, J. Wang, D. Yang, B. Li and C. Zhang, Proton Exchange Membrane Fuel Cell Reversal:A Review, Catalysts, 6, 2016, 197.R.Bashyam, J.Bellerive, P.He, Fuel cell system and method of operating fuel cell system, German Patent application DE102016207786A1 Acknowledgement We thank Volkswagen AG and Audi for funding this work. Figure 1