Effect of bipolar-plates design on corrosion,mass and heat transfer in proton-exchange membrane fuel cells and water electrolyzers:A review

Attaining a decarbonized and sustainable energy system,which is the core solution to global energy issues,is accessible through the development of hydrogen energy.Proton-exchange membrane water electrolyzers(PEMWEs)are promising devices for hydrogen production,given their high efficiency,rapid responsiveness,and compactness.Bipolar plates account for a relatively high percentage of the total cost and weight compared with other components of PEMWEs.Thus,optimization of their design may accelerate the promotion of PEMWEs.This paper reviews the advances in materials and flow-field design for bipolar plates.First,the working conditions of proton-exchange membrane fuel cells(PEMFCs)and PEMWEs are compared,including reaction direction,operating temperature,pressure,input/output,and potential.Then,the current research status of bipolar-plate substrates and surface coatings is summarized,and some typical channel-rib flow fields and porous flow fields are presented.Furthermore,the effects of materials on mass and heat transfer and the possibility of reducing corrosion by improving the flow field structure are explored.Finally,this review discusses the potential directions of the development of bipolar-plate design,including material fabrication,flow-field geometry optimization using threedimensional printing,and surface-coating composition optimization based on computational materials science.

Trifunctional robust electrocatalysts based on 3D Fe/N-doped carbon nanocubes encapsulating Co4N nanoparticles for efficient battery-powered water electrolyzers

Herein,we have designed a highly active and robust trifunctional electrocatalyst derived from Prussian blue analogs,where Co_(4)N nanoparticles are encapsulated by Fe embedded in N-doped carbon nanocubes to synthesize hierarchically structured Co_(4)N@Fe/N-C for rechargeable zinc-air batteries and overall water-splitting electrolyzers.As confirmed by theoretical and experimental results,the high intrinsic oxygen reduction reaction,oxygen evolution reaction,and hydrogen evolution reaction activities of Co_(4)N@Fe/N-C were attributed to the formation of the heterointerface and the modulated local electronic structure.Moreover,Co_(4)N@Fe/N-C induced improvement in these trifunctional electrocatalytic activities owing to the hierarchical hollow nanocube structure,uniform distribution of Co_(4)N,and conductive encapsulation by Fe/N-C.Thus,the rechargeable zinc-air battery with Co_(4)N@Fe/N-C delivers a high specific capacity of 789.9 mAh g^(-1) and stable voltage profiles over 500 cycles.Furthermore,the overall water electrolyzer with Co_(4)N@Fe/N-C achieved better durability and rate performance than that with the Pt/C and IrO2 catalysts,delivering a high Faradaic efficiency of 96.4%.Along with the great potential of the integrated water electrolyzer powered by a zinc-air battery for practical applications,therefore,the mechanistic understanding and active site identification provide valuable insights into the rational design of advanced multifunctional electrocatalysts for energy storage and conversion.

Transcriptomics integrated with metabolomics reveals the mechanism of CaCl_(2)-HCl electrolyzed water-induced glucosinolate biosynthesis in broccoli sprouts

Glucosinolates are important phytochemicals in Brassicaceae.We investigated the effect of CaCl_(2)-HCl electrolyzed water(CHEW)on glucosinolates biosynthesis in broccoli sprouts.The results showed that CHEW treatment significantly decreased reactive oxygen species(ROS)and malondialdeh yde(MDA)contents in broccoli sprouts.On the the 8^(th)day,compared to tap water treatment,the the total glucosinolate content of broccoli sprouts with CHEW treatment increased by 10.6%and calcium content was dramatically enhanced from 14.4 mg/g DW to 22.7 mg/g DW.Comparative transcriptome and metabolome analyses revealed that CHEW treatment activated ROS and calcium signaling transduction pathways in broccoli sprouts and they interacted through MAPK cascades.Besides,CHEW treatment not only promoted the biosynthesis of amino acids,but also enhanced the expression of structural genes in glucosinolate synthesis through transcription factors(MYBs,bHLHs,WRKYs,etc.).The results of this study provided new insights into the regulatory network of glucosinolates biosynthesis in broccoli sprouts under CHEW treatment.

Optimization of Channel Structure of Alkaline Water Electrolyzer by Using an Expanded Mesh as a Bipolar Plate

Alkaline water electrolysis(AWE)is the most mature technology for hydrogen production by water electrolysis.Alkaline water electrolyzer consists of multiple electrolysis cells,and a single cell consists of a diaphragm,electrodes,bipolar plates and end plates,etc.The existing industrial bipolar plate channel is concave-convex structure,which is manufactured by complicated and high-cost mold punching.This structure still results in uneven electrolyte flow and low current density in the electrolytic cell,further increasing in energy consumption and cost of AWE.Thereby,in this article,the electrochemical and flow model is firstly constructed,based on the existing industrial concave and convex flow channel structure of bipolar plate,to study the current density,electrolyte flow and bubble distribution in the electrolysis cell.The reliability of the model was verified by comparison with experimental data in literature.Among which,the electrochemical current density affects the bubble yield,on the other hand,the generated bubbles cover the electrode surface,affecting the active specific surface area and ohmic resistance,which in turn affects the electrochemical reaction.The result indicates that the flow velocity near the bottom of the concave ball approaches zero,while the flow velocity on the convex ball surface is significantly higher.Additionally,vortices are observed within the flow channel structure,leading to an uneven distribution of electrolyte.Next,modelling is used to optimize the bipolar plate structure of AWE by simulating the electrochemistry and fluid flow performances of four kinds of structures,namely,concave and convex,rhombus,wedge and expanded mesh,in the bipolar plate of alkaline water electrolyzer.The results show that the expanded mesh channel structure has the largest current density of 3330 A/m^(2)and electrolyte flow velocity of 0.507 m/s in the electrolytic cell.Under the same current density,the electrolytic cell with the expanded mesh runner structure has the smallest potential and energy consumption.This work provides a useful guide for the comprehensive understanding and optimization of channel structures,and a theoretical basis for the design of large-scale electrolyzer.

Enhancing the Efficiency of Multi-Electrolyzer Clusters with Lye Mixer:Topology Design and Control Strategy

The rise in hydrogen production powered by renewable energy is driving the field toward the adoption of systems comprising multiple alkaline water electrolyzers.These setups present various operational modes:independent operation and multi-electrolyzer parallelization,each with distinct advantages and challenges.This study introduces an innovative configuration that incorporates a mutual lye mixer among electrolyzers,establishing a weakly coupled system that combines the advantages of two modes.This approach enables efficient heat utilization for faster hot-startup and maintains heat conservation post-lye interconnection,while preserving the option for independent operation after decoupling.A specialized thermal exchange model is developed for this topology,according to the dynamics of the lye mixer.The study further details startup procedures and proposes optimized control strategies tailored to this structural design.Waste heat from the caustic fully heats up the multiple electrolyzers connected to the lye mixing system,enabling a rapid hot start to enhance the system’s ability to track renewable energy.A control strategy is established to reduce heat loss and increase startup speed,and the optimal valve openings of the diverter valve and the manifold valve are determined.Simulation results indicate a considerable enhancement in operational efficiency,marked by an 18.28%improvement in startup speed and a 6.11%reduction in startup energy consumption inmulti-electrolyzer cluster systems,particularlywhen the systems are synchronized with photovoltaic energy sources.The findings represent a significant stride toward efficient and sustainable hydrogen production,offering a promising path for large-scale integration of renewable energy.

Strategic comparison of membrane-assisted and membrane-less water electrolyzers and their potential application in direct seawater splitting(DSS)

Electrocatalytic splitting of water by means of renewable energy as the electricity supply is one of the most promising methods for storing green renewable energy as hydrogen. Although two-thirds of the earth’s surface is covered with water, there is inadequacy of freshwater in most parts of the world. Hence, splitting seawater instead of freshwater could be a truly sustainable alternative. However, direct seawater splitting faces challenges because of the complex composition of seawater. The composition, and hence, the local chemistry of seawater may vary depending on its origin, and in most cases, tracking of the side reactions and standardizing and customizing the catalytic process will be an extra challenge. The corrosion of catalysts and competitive side reactions due to the presence of various inorganic and organic pollutants create challenges for developing stable electro-catalysts. Hence, seawater splitting generally involves a two-step process, i.e., purification of seawater using reverse osmosis and then subsequent fresh water splitting. However, this demands two separate chambers and larger space, and increases complexity of the reactor design. Recently, there have been efforts to directly split seawater without the reverse osmosis step. Herein, we represent the most recent innovative approaches to avoid the two-step process, and compare the potential application of membrane-assisted and membrane-less electrolyzers in direct seawater splitting(DSS). We particularly discuss the device engineering, and propose a novel electrolyzer design strategies for concentration gradient based membrane-less microfluidic electrolyzer.

Effect of Alkaline Electrolyzed Water on Performance Improvement of Green Concrete with High Volume of Mineral Admixtures

The strength and durability of concrete will be significantly reduced at high volume of mineral admixture,and the poor early strength of concrete also still needs to be solved.In this investigation,a highly active alkaline electrolyzed waters was used as mixing water to improve the early strength and enhance the durability of green concrete with high volume mineral admixture,the influences of alkaline electrolyzed water(AEW)on hydration activity of mineral admixture and durability of concrete were determined.The results showed that compared with natural tap water,AEW can accelerate early hydration process of cement in concrete and produce comparatively more hydrated products,leading to a 13.6%higher compressive strength than that of ordinary concrete at early age,but the improvement effect of AEW concrete was relatively reduced at long-term age.Meanwhile,the activity of mineral admixtures could be stimulated by AEW to some extent,the strength and durability performance of AEW concrete after double doping 25%slag and 25%fly ash can still reach the level of ordinary cement concrete without mineral admixtures.The SEM micromorphology of 7 d hydrated natural tap water cement paste was observed to be flaky and tabular,but the AEW cement pastes present obvious cluster and granulation phenomenon.The SEM microstructure of AEW concrete with mineral admixtures is more developed and denser than ordinary tap water concrete with mineral admixtures.Therefore,the AEW probably could realize the effective utilization of about 50%mineral admixture amount of concrete without strength loss,the cement production cost and associated CO_(2) emission reduced,which has a good economic and environmental benefit.

An effective oxygen electrode based on Ir0.6Sn0.4O2 for PEM water electrolyzers

An effective oxygen evolution electrode with Ir0.6Sn0.4O2 was designed for proton exchange membrane(PEM)water electrolyzers.The anode catalyst layer exhibits a jagged structure with smaller particles and pores,which provide more active sites and mass transportation channels.The prepared IrSn electrode showed a cell voltage of 1.96 V at 2.0 A cm^-2 with Ir loading as low as 0.294 mg cm^-2.Furthermore,Ir Sn electrode with different anode catalyst loadings was investigated.The IrS n electrode indicates higher mass current and more stable cell voltage than the commercial Ir Black electrode at low loading.

Technical factors affecting the performance of anion exchange membrane water electrolyzer

Anion exchange membrane(AEM)electrolysis is a promising membrane-based green hydrogen production technology.However,AEM electrolysis still remains in its infancy,and the performance of AEM electrolyzers is far behind that of well-developed alkaline and proton exchange membrane electrolyzers.Therefore,breaking through the technical barriers of AEM electrolyzers is critical.On the basis of the analysis of the electrochemical performance tested in a single cell,electrochemical impedance spectroscopy,and the number of active sites,we evaluated the main technical factors that affect AEM electrolyzers.These factors included catalyst layer manufacturing(e.g.,catalyst,carbon black,and anionic ionomer)loadings,membrane electrode assembly,and testing conditions(e.g.,the KOH concentration in the electrolyte,electrolyte feeding mode,and operating temperature).The underlying mechanisms of the effects of these factors on AEM electrolyzer performance were also revealed.The irreversible voltage loss in the AEM electrolyzer was concluded to be mainly associated with the kinetics of the electrode reaction and the transport of electrons,ions,and gas-phase products involved in electrolysis.Based on the study results,the performance and stability of AEM electrolyzers were significantly improved.

Advances and challenges of electrolyzers for large-scale CO_(2) electroreduction

CO_(2) electroreduction(CO_(2) ER)to high value-added chemicals is considered as a promising technology to achieve sustainable carbon neutralization.By virtue of the progressive research in recent years aiming at design and understanding of catalytic materials and electrolyte systems,the CO_(2) ER performance(such as current density,selectivity,stability,CO_(2) conversion,etc.)has been continually increased.Unfortunately,there has been relatively little attention paid to the large-scale CO 2 electrolyzers,which stand just as one obstacle,alongside series-parallel integration,challenging the practical application of this infant technology.In this review,the latest progress on the structures of low-temperature CO_(2) electrolyzers and scale-up studies was systematically overviewed.The influence of the CO_(2) electrolyzer configurations,such as the flow channel design,gas diffusion electrode(GDE)and ion exchange membrane(IEM),on the CO_(2) ER performance was further discussed.The review could provide inspiration for the design of large-scale CO_(2) electrolyzers so as to accelerate the industrial application of CO_(2) ER technology.

Activation of iridium site by anchoring ruthenium atoms on defects for efficient anodic catalyst in polymer electrolyte membrane water electrolyzers

1.Introduction Hydrogen is an ideal energy carrier to tackle the energy crisis and greenhouse effect,because of its high energy density and low emission.The production,storage and transportation of hydrogen are key factors to the practical application of hydrogen energy.As the scientific and technological understanding of the electrochemical devices was advancing in the past few decades,water electrolyzers based on the proton exchange membrane (PEM) have attracted much focus for its huge potential on the production of hydrogen via water splitting.PEM electrolyzers use perfluorinated sulfonic acid (PFSA) based membranes as the electrolyte.

Electrolyzed Oxidized Water (EOW): Non-Thermal Approach for Decontamination of Food Borne Microorganisms in Food Industry

Electrolyzed Oxidized Water (EOW) is produced by passing a diluted salt solution through an electrolytic cell, having anode and cathode electrodes. The anode and cathode are separated by a bipolar membrane. Negatively charged ions—chloride and hydroxide in the diluted salt solution move to anode to give up electrons and become gas (O2, Cl2) and hypochlorous acid and having redox potential of +700 to +800 mV with pH 4.0. It has a strong oxidation potential and a shortage of electrons giving it the ability to oxidize and sterilize. In microbial inactivation process, oxidized water damage cell membranes, create disruption in cell metabolic processes and essentially kill the cell. EOW, also a strong acid, is different to hydrochloric acid or sulfuric acid in that it is not corrosive to skin, mucous membrane, or organic material. It is easy to handle and suitable for the sanitation of the plant and decontamination of foods. Electrolyzed water has been tested and used as a disinfectant in the food industry and other applications.

Hydrogen Production from an Alkali Electrolyzer Operating with Egypt Natural Resources

Egypt is bordered by coastal sea2450 km, while incident solar radiation is in the order of magnitudes of 1900-2200 W/m2 in that area of the world. The present work is aimed to assess the hydrogen production from the solar-hydrogen system composed of photovoltaic cell motivated by solar energy and supplies electricity to alkali electrolyzer. The electrolyzer uses sea and Nile water as electrolytes. Indoor tests are done to identify the optimum concentration ratio of the sea water to produce hydrogen. Experimental results showed that stand-alone sea water gives a higher production rate. The results of the outdoor tests revealed the need for about seven units of electrolyzer working with the sea water to produce the same amount of hydrogen that KOH solution electrolyte would provide. However, the efficiency of solar-hydrogen units working with the sea water gives a lower constant efficiency of about 0.13%, followed by Photovoltaic/electrolyzer unit using Nile water of approximately 0.005%. The KOH solution electrolyte provides an efficiency of approximately 8% at solar noon. The sea water is recommended to be used instead of KOH solution in all coming electrolyzers.

MATLAB/Simulink Modeling and Experimental Resultsof a PEM Electrolyzer Powered by a Solar Panel

In this paper, the solar panels are used to power an electrolyzer to separate the water into hydrogen and oxygen gas. Theelectrical equivalent circuit for the proton exchange membrane electrolyzer was developed and implemented in MATLAB/Simulinkalong with the atmospheric hydrogen storage tank. The voltage （2 volt） and current （1 ampere） were supplied in a similar manner inorder to compare the simulated and experimental results. The hydrogen amount is calculated to be 7.345 （ml/min A） from the modelas well as the experimental set-up. The experimental and simulation results were matched.

Influence of surfactants on selective mechanical separation of fine active materials used in high temperature electrolyzers contributing to circular economy

As one of the promising hydrogen production technologies,the development of water electrolysis systems including recycling of their functional components is actively investigated.However,the focus lies on energy and chemical intensive metallurgical operations and less on mechanical separation processes in most studies.Here,an innovative surfactant-based separation process(using CTAB and SDS)is investigated to contribute to developing a selective physical separation process for ultrafine particles used in high temperature water electrolyzers(composed of NiO,LSM,ZrO_(2),and YSZ).Their different surface charge in alkaline solutions influences the adsorption of surfactants on particle surfaces as well as the modification of particulate wettability,which is a key separation feature.Through the observations of changes in surface charge and wetting behavior in the presence of surfactants,a feasibility of liquid-liquid particle separation(LLPS)is evaluated.The performance of LLPS with model particle mixtures shows the potential of selective separation with recovery of NiO in the organic phase,while the rest of the particles remain in the aqueous phase.Perovskite LSM is not considered in this system because it shows a high possibility of being recovered by magnetic separation.The proposed process can be further optimized by increasing the phase separation stages,and further research is needed on the NiO phase,which showed exceptional behavior in the presence of the surfactants.

Understanding the Temperature Effect on Carbon-Carbon Coupling during CO_(2)and CO Electroreduction in Zero-Gap Electrolyzers

Comprehensive Summary Cu-catalyzed electrochemical CO_(2)reduction reaction(CO_(2)RR)and CO reduction reaction(CORR)are of great interest due to their potential to produce carbon-neutral and value-added multicarbon(C2+)chemicals.In practice,CO_(2)RR and CORR are typically operated at industrially relevant current densities,making the process exothermal.Although the increased operation temperature is known to affect the performance of CO_(2)RR and CORR,the relationship between temperatures and kinetic parameters was not clearly elaborated,particularly in zero-gap reactors.In this study,we detail the effect of the temperature on Cu-catalyzed CO_(2)RR and CORR.Our electrochemical and operando spectroscopic studies show that high temperatures increase the activity of CO_(2)RR to CO and CORR to C2H4 by enhancing the mass transfer of CO_(2)and CO.As the rates of these two processes are highly influenced by reactant diffusion,elevating the operating temperature results in high local CO_(2)and CO availability to accelerate product formation.Consequently,the*CO coverage in both cases increases at higher temperatures.However,under CO_(2)RR conditions,*CO desorption is more favorable than carbon-carbon(C—C)coupling thermodynamically at high temperatures,causing the reduction in the Faradaic efficiency(FE)of C_(2)H_(4).In CORR,the high-temperature-augmented CO diffusion overcomes the unfavorable adsorption thermodynamics,increasing the probability of C—C coupling.

Effects of high-pressure activated slightly acidic electrolyzed water on cleaning and sterilization of pig transfer vehicles

The establishment of biosafety system is of enormous importance to the livestock and poultry production in terms of mitigating the transmission of diseases and implementing regional prevention and control measures.However,the current sterilization technology presents several drawbacks,including time-consuming procedures,chemical residues,and challenges in treating the sewage after rinsing.In this study,a novel cleaning and sterilization method that combines slightly acidic electrolyzed water and high pressure water-jet was developed.An orthogonal test was conducted to examine the correlation between high-pressure conditions and the various non-structural parameters on the efficacy of sterilization rate.In a field test,the effectiveness of the technology in cleaning pig transfer vehicles was evaluated by the total plate count and variations of community composition.The findings revealed that the combination of process parameters,including an available chlorine concentration of 200 mg/L,rinsing pressure of 170 bar,rinsing duration of 10 s,and residence time of 15 min,resulted in a removal rate of colony concentration on the surface of pig transfer vehicles of(96.50±0.91)%.Moreover,it was demonstrated to effectively inhibit a variety of pathogenic bacteria.The innovative cleaning system has the potential to replace traditional methods and reduces pollution while saving time and labor.It introduces a novel approach for sterilization of transportation in livestock and poultry farms as well as the biosafety construction of the animal husbandry.

Progresses on two-phase modeling of proton exchange membrane water electrolyzer

The Proton Exchange Membrane(PEM)water electrolyzer is considered one of the promising energy storing means for harnessing variable renewable energy sources to produce hydrogen.Understanding the internal fluid dynamics,which are often challenging to directly observe experimentally,has prompted the use of numerical models to investigate two-phase flow within PEM water electrolyzers.In this study,we provide a comprehensive review of prior research focusing on two-phase modeling of PEM electrolyzers,encompassing both components at mesoscopic scales and the full electrolyzer at the macroscopic level.We delve into the specifics of various modeling approaches for two-phase flow at different scales and summarize and discuss the current state of the art in the field.Presently,two-phase models for the full electrolyzer predominantly employ a macroscopic homogeneous assumption.However,mesoscopic and microscopic models capable of tracking phase interfaces are limited to components.Challenges persist in integrating various modeling scales into a comprehensive electrolyzer model,particularly in coupling two-phase flow between the channels and porous media.Future efforts should focus on developing multi-scale models and simulating two-phase flow under fluctuating input conditions.Additionally,given the structural similarities between PEM water electrolyzers and PEM fuel cells,we compare and discuss differences in two-phase modeling between the two technologies.This work offers the insights for researchers in the field of modeling of PEM water electrolyzers and even fuel cells.

Conception of a new 4-quadrant hydrogen compressed air energy storage power plant with an integrated electrolyzer

A hydrogen compressed air energy storage power plant with an integrated electrolyzer is ideal for large-scale,long-term energy storage because of the emission-free operation and the possibility to offer multiple ancillary services on the German energy market.This paper defines analyzes such a storage concept and conducts an extensive comparison with four additional storage concepts based on various criteria.The results show that the combination of storing compressed air and hydrogen offers a higher efficiency than storing only hydrogen and lower specific investment costs than storing only compressed air.This result is confirmed with analysis of the optimal sizing of each power plant component for simultaneous participation on multiple energy markets with a linear optimization dispatch mode.The hydrogen compressed air energy storage(HCAES)power plant can utilize more revenue possibilities than a hydrogen energy storage because of the higher round-trip efficiency and the combination of the air compressor and the integrated electrolyzer during charging mode.The integration of the electrolyzer,however,offers a couple of challenges itself because of the highly flexible operation mode.A new concept for the controllable 24-pulse diode-thyristor rectifier of the electrolyzer is presented,that uses mostly common components while offering little to no grid harmonics and a long lifetime.The flexible integrated electrolyzer allows for the 4-quadrant operation of the storage power plant.

Electrolyzed water and its application in animal houses

Electrolyzed water(EW) can be produced by electrolysis of a dilute salt solution. Slightly acidic electrolyzed water(SAEW, p H 5.0–6.5) and neutral electrolyzed water(NEW, p H 6.5–8.5) are considered healthy and environmentally friendly because no hazardous chemicals are added in its production, there is reduced corrosion of surfaces and it minimizes the potential for damage to animal and human health. Over the last decade, EW has become increasingly popular as an alternative disinfectant for decontamination in animal houses. However, there have been some issues related to EW that are not well known, including different mechanisms for generation of SAEW and NEW, and the antimicrobial mechanism of EW. This review covers the definitions of SAEW and NEW, different generation systems for SAEW and NEW, the antimicrobial mechanism of EW, and recent developments related to the application of SAEW and NEW in animal houses.