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.

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.

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.

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.

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.

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.

Boosting Oxygen Evolution Reaction Performance on NiFe‑Based Catalysts Through d‑Orbital Hybridization

Anion-exchange membrane water electrolyzers(AEMWEs)for green hydrogen production have received intensive attention due to their feasibility of using earth-abundant NiFe-based catalysts.By introducing a third metal into NiFe-based catalysts to construct asymmetrical M-NiFe units,the d-orbital and electronic structures can be adjusted,which is an important strategy to achieve sufficient oxygen evolution reaction(OER)performance in AEMWEs.Herein,the ternary NiFeM(M:La,Mo)catalysts featured with distinct M-NiFe units and varying d-orbitals are reported in this work.Experimental and theoretical calculation results reveal that the doping of La leads to optimized hybridization between d orbital in NiFeM and 2p in oxygen,resulting in enhanced adsorption strength of oxygen intermediates,and reduced rate-determining step energy barrier,which is responsible for the enhanced OER performance.More critically,the obtained NiFeLa catalyst only requires 1.58 V to reach 1 A cm^(−2) in an anion exchange membrane electrolyzer and demonstrates excellent long-term stability of up to 600 h.

CO2 electrolysis at industrial current densities using anion exchange membrane based electrolyzers

Significant progress on electrocatalytic CO2 reduction reaction (CO2RR) has been achieved in recent years.However,the research and development of electrolyzer device for CO2RR is scarce.Here we use anion exchange membrane to develop zerogap electrolyzers for CO2RR.The electrochemical properties of the electrolyzers with Pd/C and Cu cathodes are investigated.The Pd/C cathode shows a current density of 200 mA cm^-2with CO Faradaic efficiency of 98%and energy efficiency of 48.8%,while the Cu cathode shows a current density of 350 mA cm^-2with total CO2RR Faradaic efficiency of 81.9%and energy efficiency of 30.5%.This work provides a promising demonstration of CO2 electrolyzer using anion exchange membrane for CO2 electrolysis at industrial current densities.

Selenium vacancies regulate d-band centers in Ni_(3)Se_(4)toward paired electrolysis in anion-exchange membrane electrolyzers for upgrading N-containing compounds

Paired electrolysis in anion-exchange membrane(AEM)electrolyzers toward the cathodic nitrate reduction reaction(NO_(3)RR)and anodic benzylamine oxidation reaction(BOR)could generate high value-added N-containing compounds simultaneously.The key challenge is to develop bifunctional electrocatalysts with a wide potential window,which can achieve highly efficient conversion of anode and cathode reactants.Herein,Ni_(3)Se_(4)with Se vacancies was prepared and employed as the cathode and anode of AEM electrolyzers for NO_(3)RR and BOR.^(15)N isotope-labeling online differential electrochemical mass spectrometry(DEMS)proved that ammonium was reduced from nitrates and revealed the reaction pathway of NO_(3)RR.The density functional theory calculation clarified that Se vacancies regulate d-band centers,and then further modulate the adsorption energy of adsorbed hydrogen,NO_(3)^(-)and intermediates on the Ni_(3)Se_(4)-60s surface in NO_(3)RR,so as to optimize the hydrogenation of NO_(3)^(-)into ammonia.Moreover,during the BOR,the Se vacancy can promote the adsorption of OH^(-),which is easier to form the active species of Ni OOH.The technical and economic evaluation exhibited that the cost of paired electrolysis is 1.21 times lower and the profit is 1.42 times higher than that of the unpaired electrolysis,which shows the economic attraction of paired electrolysis.This work delivers the guidance for the design of efficient catalysts for paired electrolysis in AEM electrolyzer toward the sustainable synthesis of value-added chemicals.

Electrocatalytic CO_(2)reduction to syngas

While carbon dioxide(CO_(2))is a major greenhouse gas,it is also an important C1 resource.In the trend of energy conservation and emission reduction,electrocatalytic reduction has become a very promising strategy for CO_(2)utilization because it can convert CO_(2)directly to high-valued chemicals and fuels under mild conditions.In particular,the product CO and by-product H_(2)can be combined into syngas by an electrocatalytic CO_(2)reduction reaction(CO_(2)RR)in an aqueous medium.Different molar ratios of CO and H_(2)may be used to produce essential bulk chemicals or liquid fuels such as methanol,alkanes,and olefins through thermochemical catalysis,Fischer-Tropsch synthesis,microbial fermentation,and other techniques.This work discusses the latest strategies in controlling the molar ratio of CO/H_(2)and improving the yield of CO_(2)RR-to-syngas.The challenges of electrocatalytic syngas production are analyzed from an industrial application perspective,and the possible measures to overcome them are proposed in terms of new catalyst design,electrolyte innovation,flow reactor optimization,anodic reaction coupling,and operando technique application.

A Cu-Pd alloy catalyst with partial phase separation for the electrochemical CO_(2) reduction reaction

Cu catalysts can convert CO_(2) through an electrochemical reduction reaction into a variety of useful carbon-based products.However,this capability provides an obstacle to increasing the selectivity for a single product.Herein,we report a simple fabrication method for a Cu-Pd alloy catalyst for use in a membrane electrode assembly(MEA)-based CO_(2) electrolyzer for the electrochemical CO_(2) reduction reaction(ECRR)with high selectivity for CO production.When the composition of the Cu-Pd alloy catalyst was fabricated at 6:4,the selectivity for CO increased and the production of multi-carbon compounds and hydrogen is suppressed.Introducing a Cu-Pd alloy catalyst with 6:4 ratio as the cathode of the MEAbased CO_(2) electrolyzer showed a CO faradaic efficiency of 92.8%at 2.4 V_(cell).We assumed that these results contributed from the crystal planes on the surface of the Cu-Pd alloy.The phases of the Cu-Pd alloy catalyst were partially separated through annealing to fabricate a catalyst with high selectivity for CO at low voltage and C_(2)H_4 at high voltage.The results of CO-stripping testing confirmed that when Cu partially separates from the lattice of the Cu-Pd alloy,the desorption of~*CO is suppressed,suggesting that C-C coupling reaction is favored.

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.

Pulsed laser interference patterning of transition-metal carbides for stable alkaline water electrolysis kinetics

We investigated the role of metal atomization and solvent decomposition into reductive species and carbon clusters in the phase formation of transition-metal carbides(TMCs;namely,Co_(3)C,Fe_(3)C,TiC,and MoC)by pulsed laser ablation of Co,Fe,Ti,and Mo metals in acetone.The interaction between carbon s-p-orbitals and metal d-orbitals causes a redistribution of valence structure through charge transfer,leading to the formation of surface defects as observed by X-ray photoelectron spectroscopy.These defects influence the evolved TMCs,making them effective for hydrogen and oxygen evolution reactions(HER and OER)in an alkaline medium.Co_(3)C with more oxygen affinity promoted CoO(OH)intermediates,and the electrochemical surface oxidation to Co_(3)O_(4)was captured via in situ/operando electrochemical Raman probes,increasing the number of active sites for OER activity.MoC with more d-vacancies exhibits strong hydrogen binding,promoting HER kinetics,whereas Fe_(3)C and TiC with more defect states to trap charge carriers may hinder both OER and HER activities.The results show that the assembled membrane-less electrolyzer with Co_(3)C∥Co_(3)C and MoC∥MoC electrodes requires~2.01 and 1.99 V,respectively,to deliver a 10 mA cm−2 with excellent electrochemical and structural stability.In addition,the ascertained pulsed laser synthesis mechanism and unit-cell packing relations will open up sustainable pathways for obtaining highly stable electrocatalysts for electrolyzers.

Towards high-performance and robust anion exchange membranes(AEMs)for water electrolysis:Super-acid-catalyzed synthesis of AEMs

The increasing demand for hydrogen energy to address environmental issues and achieve carbon neutrality has elevated interest in green hydrogen production,which does not rely on fossil fuels.Among various hydrogen production technologies,anion exchange membrane water electrolyzer(AEMWE)has emerged as a next-generation technology known for its high hydrogen production efficiency and its ability to use non-metal catalysts.However,this technology faces significant challenges,particularly in terms of the membrane durability and low ionic conductivity.To address these challenges,research efforts have focused on developing membranes with a new backbone structure and anion exchange groups to enhance durability and ionic conductivity.Notably,the super-acid-catalyzed condensation(SACC)synthesis method stands out due to its user convenience,the ability to create high molecular weight(MW)polymers,and the use of oxygen-tolerant organic catalysts.Although the synthesis of anion exchange membranes(AEMs)using the SACC method began in 2015,and despite growing interest in this synthesis approach,there remains a scarcity of review papers focusing on AEMs synthesized using the SACC method.The review covers the basics of SACC synthesis,presents various polymers synthesized using this method,and summarizes the development of these polymers,particularly their building blocks including aryl,ketone,and anion exchange groups.We systematically describe the effects of changes in the molecular structure of each polymer component,conducted by various research groups,on the mechanical properties,conductivity,and operational stability of the membrane.This review will provide insights into the development of AEMs with superior performance and operational stability suitable for water electrolysis applications.

Generation of input spectrum for electrolysis stack degradation test applied to wind power PEM hydrogen production

Hydrogen production by proton exchange membrane electrolysis has good fluctuation adaptability,making it suitable for hydrogen production by electrolysis in fluctuating power sources such as wind power.However,current research on the durability of proton exchange membrane electrolyzers is insufficient.Studying the typical operating conditions of wind power electrolysis for hydrogen production can provide boundary conditions for performance and degradation tests of electrolysis stacks.In this study,the operating condition spectrum of an electrolysis stack degradation test cycle was proposed.Based on the rate of change of the wind farm output power and the time-averaged peak-valley difference,a fluctuation output power sample set was formed.The characteristic quantities that played an important role in the degradation of the electrolysis stack were selected.Dimensionality reduction of the operating data was performed using principal component analysis.Clustering analysis of the data segments was completed using an improved Gaussian mixture clustering algorithm.Taking the annual output power data of wind farms in Northwest China with a sampling rate of 1 min as an example,the cyclic operating condition spectrum of the proton-exchange membrane electrolysis stack degradation test was constructed.After preliminary simulation analysis,the typical operating condition proposed in this paper effectively reflects the impact of the original curve on the performance degradation of the electrolysis stack.This study provides a method for evaluating the degradation characteristics and system efficiency of an electrolysis stack due to fluctuations in renewable energy.

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.

Modeling of Large-Scale Hydrogen Storage System Considering Capacity Attenuation and Analysis of Its Efficiency Characteristics

In the existing power system with a large-scale hydrogen storage system,there are problems such as low efficiency of electric-hydrogen-electricity conversion and single modeling of the hydrogen storage system.In order to improve the hydrogen utilization rate of hydrogen storage system in the process of participating in the power grid operation,and speed up the process of electric-hydrogen-electricity conversion.This article provides a detailed introduction to the mathematical and electrical models of various components of the hydrogen storage unit,and also establishes a charging and discharging efficiency model that considers the temperature and internal gas partial pressure of the hydrogen storage unit.These models are of great significance for studying and optimizing gas storage technology.Through these models,the performance of gas storage units can be better understood and improved.These studies are very helpful for improving energy storage efficiency and sustainable development.The factors affecting the charge-discharge efficiency of hydrogen storage units are analyzed.By integrating the models of each unit and considering the capacity degradation of the hydrogen storage system,we can construct an efficiency model for a large hydrogen storage system and power conversion system.In addition,the simulation models of the hydrogen production system and hydrogen consumption system were established in MATLAB/Simulink.The accuracy and effectiveness of the simulation model were proved by comparing the output voltage variation curve of the simulation with the polarization curve of the typical hydrogen production system and hydrogen consumption system.The results show that the charge-discharge efficiency of the hydrogen storage unit increases with the increase of operating temperature,and H2 and O2 partial voltage have little influence on the charge-discharge efficiency.In the process of power conversion system converter rectification operation,its efficiency decreases with the increase of temperature,while in the process of inverter operation,power conversion system efficiency increases with the increase of temperature.Combined with the efficiency of each hydrogen storage unit and power conversion system converter,the upper limit of the capacity loss of different hydrogen storage units was set.The optimal charge-discharge efficiency of the hydrogen storage system was obtained by using the Cplex solver at 36.46%and 66.34%.

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.