Electrochemical Hydrogen Compression Research Articles

Robust and highly proton conductive COF composite membranes for fuel cell and electrochemical hydrogen compression

Robust and highly conductive proton exchange membrane (PEM) is the unremitting pursuit of numerous electrochemical energy technologies such as fuel cell and the emerging electrochemical hydrogen compression. Ionic covalent organic framework nanosheets (iCONs) with long-range ordered nanochannels and abundant ionic groups show substantial potential as next-generation PEM materials. However, it is challenging to assemble iCONs into membranes with both robustness and flexibility due to the electrostatic repulsion and rigid framework. Herein, we propose a hydrogen-bond binding strategy to fabricate sulfonic iCON (SCON) composite membranes by co-assembling tannic acid (TA) nanoaggregates and SCONs. The abundant and dynamically reversible hydrogen-bond interactions introduced by TA nanoaggregates establish effective linkage between SCONs and allow some restricted movements, endowing membranes with remarkably improved mechanical properties. The stacked SCONs construct long-range ordered nanochannels with well-arranged sulfonic groups in membranes, and the hydrogen-bond networks further facilitate the proton transport through Grotthuss mechanism. Consequently, TA/SCON composite membranes displays significantly enhanced tensile strength of 101.9 MPa, good flexibility and high proton conductivity of 490.1 mS cm−1 at 80 °C and 100 % RH simultaneously. This hydrogen-bond binding strategy offers a promising approach to fabricate robust and highly conductive PEMs for various proton-conducting applications.

Optimal sizing and operation of electrochemical hydrogen compression

Hydrogen compression is necessary for efficient hydrogen storage, transportation, and in high-pressure chemical processes. A promising alternative to traditional mechanical compressors is electrochemical compression. As a novel technology, there are still open questions regarding the optimal design and operation in terms of total cost and the influence of the pressure level on the optimal operating point. We analyze the efficiency and economic performance of such compression. We develop a dynamic and spatially distributed (1D) model of an electrochemical hydrogen compressor. We investigate hydrogen compression at low to high pressure levels. Moreover, an operational and capital cost analysis is performed, and the optimal current density and temperature are determined. The results reveal that lower temperatures, and higher current densities tend to be favorable at higher target pressures. The optimal total cost for the considered compressor varies from 0.6 ▪ to 2 ▪ for compression to 1 MPa and 70 MPa, respectively.

Influence of key design variables on the performance and mechanical behavior of an electrochemical hydrogen compressor

This study examines the impact of key design variables on the water management, mechanical responses, and overall performance of an Electrochemical Hydrogen Compressor (EHC) cell. A previously developed three-dimensional (3-D) computational model of EHC is applied to different EHC cell geometries, varying in the thicknesses of membranes and the gas diffusion layer (GDL), as well as the widths of the channel and rib in the flow field. Generally, the model's predictions align well with the experimental data measured across a broad spectrum of operating current densities, revealing the intricate interaction between electrochemical/transport phenomena and the mechanical behaviors within the EHC cell. Thinner membranes provide enhanced performance by reducing water shortage at the anode, while increased GDL thickness significantly mitigates cell deformation and stress concentration. Changes in the widths of the rib and channel exert minimal influence on water transport behaviors and cell performance, but they substantially impact mechanical stability. This study underlines the necessity of fine-tuning EHC design factors to strike a balance between mechanical stability and cell performance, thus aiding the practical implementation of EHC technology.

Covalent organic frameworks with flexible side chains in hybrid PEMs enable highly efficient proton conductivity.

Electrochemical hydrogen compression (EHC) is an emerging energy conversion technology. Proton exchange membranes (PEMs) with high proton conductivity and high mechanical strength are highly required to meet the practical requirements of EHC. Herein, ionic covalent organic frameworks (iCOFs) with tunable side chains were synthesized and introduced into the sulfonated poly (ether ether ketone) (SPEEK) matrix to fabricate hybrid PEMs. In our membranes, the rigid iCOFs afford ordered proton conduction channels, whereas the flexible side chains on iCOFs afford abundant proton conduction sites, adaptive hydrogen bonding networks, and high local density short hydrogen bonds for highly efficient proton transport. Moreover, the hydrogen bond interactions between the side chains on iCOFs and the SPEEK matrix enhance the mechanical stability of membranes. As a result, the hybrid PEM acquires an enhanced proton conductivity of 540.4 mS cm-1 (80 °C, 100%RH), a high mechanical strength of 120.41 MPa, and a superior performance (2.3 MPa at 30 °C, 100%RH) in EHC applications.

Production of Novel Tubular Electrochemical Hydrogen Compressor

For most applications, especially transport, hydrogen needs to be compressed due to its low volumetric density. Conventionally, mechanical compressors are used for hydrogen compression, but they possess disadvantages such as high maintenance due to moving parts and a limited one-stage compression ratio. A promising technology to overcome those obstacles is electrochemical hydrogen compression, in which hydrogen is compressed in an electrochemical membrane reactor.To date, only planar electrochemical reactors for hydrogen compression have been investigated although tubular designs offer advantages in membrane area to reactor volume ratio, sealing options, pressure stability and reactor complexity. However, high contact and membrane resistances and scalable manufacturing processes are still challenges to be addressed for the advent of tubular electrochemical compressors in application.Herein we introduce a manufacturing process for tubular electrochemical hydrogen compression reactors. The developed cell comprises a catalyst coated porous tubular anode covered by a tubular proton exchange membrane, which was subsequently coated with the cathode catalyst layer. The porous anode was prepared via metal 3D printing. 3D printing enables tailored porosity and geometry by which mass transport is enhanced. The catalyst layer was applied by manual spray coating. Constant current experiments and electrochemical impedance spectroscopy were performed to characterize the as prepared tubular electrochemical compressor. The results revealed the importance of tailored contacting concepts and the optimization of components regarding water transport, as the efficiency of the process is dominated by contact and membrane resistances.

(Invited) Parametric Investigation of Electrochemical Hydrogen Compression: An Experimental Study

The rising global demand for energy has been primarily met by fossil fuels resulting in environmental threats like global warming and climate change. Hydrogen can play a key role in combating climate change because it represents a carbon-free energy pathway when it is produced renewably. The chemical energy in hydrogen can be converted with high efficiency to electricity using fuel cells with water as the only byproduct. However, the establishment of the hydrogen infrastructure still poses significant challenges, particularly in the area of storage. Due to its low density, hydrogen is difficult to store either as a compressed gas or a liquid. Mechanical compressors are typically used to compress hydrogen, but their complex design and maintenance requirements add to their cost.Electrochemical compression (ECC) represents a viable alternative to mechanical compressors due to its higher efficiency, lack of moving parts, noiseless and vibration-free operation, and modularity. ECC is an electrochemical device that employs a proton exchange membrane (PEM) to compress hydrogen. It operates by applying a voltage across the PEM while supplying low-pressure hydrogen to the anode. The applied voltage initiates the oxidization of hydrogen into protons and electrons. The protons migrate through the PEM towards the cathode, while the electrons are directed towards the cathode through the external circuit by the power source. Upon reaching the cathode, the protons and electrons recombine to produce hydrogen at a higher pressure. Furthermore, ECC offers additional advantages such as the ability to separate and purify hydrogen from a gaseous mixture.For the successful commercialization of ECC, it is essential to achieve high performance with minimal energy consumption. This work presents a detailed parametric investigation of electrochemical hydrogen compression conducted experimentally using a single cell ECC apparatus. The effects of key parameters including voltage, temperature, membrane thickness, and relative humidity on ECC performance are examined for two outlet variables, viz. discharge pressure and gas throughput. We also elucidate the adverse effect of back diffusion due to the high pressure differential between cathode and anode compartments on the overall ECC performance. Various ECC performance metrics such as output pressure, current density, net flux, and compression efficiency are investigated as a function of the operating parameters. The results show that tradeoffs are required to achieve different objectives. For example, operating at a higher voltage is favorable for both discharge pressure and gas throughput but at the cost of reduced ECC efficiency due to increased back diffusion. The results also show that a lower operating temperature favors higher discharge pressures, whereas a higher temperature favors higher gas throughput. Similarly, thinner membranes facilitate a higher gas throughput due to reduced ohmic resistance, while thicker membranes can mitigate back diffusion thereby yielding higher discharge pressures. Furthermore, operating at higher RH is beneficial for both the discharge pressure and gas throughput.These results provide valuable insights on the effect of various operating parameters on ECC performance. This study confirms that back diffusion plays a deleterious role in ECC operation and must be given careful consideration in stack design. Also, novel PEMs with low hydrogen permeability should be identified to optimize ECC performance. The results suggest that ECC is a promising alternative to conventional technologies for hydrogen compression.

Incorporating graphene oxide into COF membranes enables ultrahigh proton conductivity and ultralow H2 crossover

Proton exchange membranes (PEMs) are the core components of electrochemical hydrogen energy production, storage and conversion devices. It is a great challenge to develop PEMs with a combination of high proton conductivity, minimal H2 crossover and mechanical robustness for achieving high efficiency and long-term stability in these devices. Here, a co-assembled PEM composed of ionic covalent organic framework (iCOF) nanosheets and functionalized graphene oxide (GO) nanosheets was presented. The iCOF (TpPa-SO3H) nanosheets and polydopamine-modified graphene oxide (DGO) nanosheets were co-assembled into TpPa-SO3H/DGO mixed nanosheets with ultrahigh aspect ratio, which were readily further processed into TpPa-SO3H/DGO co-assembled membranes. The abundant and uniformly distributed –SO3H groups on TpPa-SO3H nanosheets and the acid-base pairs formed between TpPa-SO3H and DGO nanosheets promoted proton conduction significantly. Additionally, the dense structured DGO nanosheets inhibited H2 crossover remarkably, and the multiple interactions between TpPa-SO3H and DGO nanosheets enhanced mechanical strength. The resultant TpPa-SO3H/DGO co-assembled membrane exhibited an ultrahigh proton conductivity of 916.4 mS cm−1 (80 °C, 100% RH), an unprecedently low H2 crossover of 9.7 barrer and a sufficient tensile stress of 87.8 MPa. The enhanced proton conduction and H2 barrier property led to enhanced performance in both electrochemical hydrogen compression and single hydrogen fuel cells.

Dynamic Modeling and Operation of a Green Hydrogen Fueling Station for Heavy-Duty Fuel Cell Vehicles

Hydrogen fuel cell electric vehicles (FCEVs) have increased driving ranges and faster refueling times than battery electric vehicles (BEVs). The driving range of FCEVs can be increased by increasing the size, quantity or operating pressure of on-board hydrogen storage tanks at a lower weight and cost than increasing the size or number of Li-ion battery packs in BEVs. Ffast-refueling leads to less waiting time at the fueling station for high-utilization commercial vehicles. As a result, fuel cell system heavy-duty vehicles (HDV) are attracting more attention [1]. Currently, the lack of a hydrogen refueling infrastructure is limiting FCEV adoption. Since the driving routes of HDV trucks are more predictable, a small number of strategically located fueling stations could service pre-planned truck driving routes [2]. While hydrogen refueling protocols and fueling stations for light-duty vehicles (LDV) have been extensively studied [3,4,5], HDV trucks have different refueling protocols and operating conditions (e.g. mass holdup, pressure, refueling rate). To our knowledge, little work has been done on modeling hydrogen fueling stations for HDV trucks applications. With this motivation, a dynamic model of a truck stop coupled with green hydrogen production has been developed for fleet HDV trucks. At the truck stop, green hydrogen is produced from water electrolysis using solar photovoltaics (PV). Electrochemical hydrogen compression (EHC) is implemented for high-pressure hydrogen storage and dispensing. The fluctuations from solar PV and truck hydrogen demand are actively managed by installation of a spherical hydrogen storage vessel. The feasibility and flexibility of a truck stop using 100% renewable electricity and hydrogen will be discussed.A high-fidelity dynamic model of a Proton Exchange Membrane (PEM) electrolyzer is developed for hydrogen production from PV electricity. A PEM electrochemical hydrogen compressor model is developed for gas pressurization with consideration of EHC temperature and water management. The green hydrogen is stored in a large spherical storage vessel to decouple the different PV power loads and HDV trucks hydrogen refueling demands. A modular system for HDV trucks refueling (nominal working pressure of 35 MPa) is designed and modeled with parallel multi-stage hydrogen compression and cascaded storage tanks. It was found that single modular system for FCEV refueling shows a service gap during hydrogen cascaded storage tank refilling, but a multiple modular structure can be easily expanded and provide uninterrupted hydrogen for FCEV refueling.The different hydrogen production and dispensing scenarios are implemented depending on the seasonal solar supply and varied HDV trucks demands. Hydrogen compression using mechanical compressor and electrochemical compressor are compared. The truck stop operation strategies are proposed based on the integrated process systems analysis of solar penetrations, hydrogen production and compression, and HDV trucks demand. The feasibility and flexibility of truck stop fueled by solar energy provide an insight for the transition to Net Zero Emission Transportation.[1] Cullen, D.A., Neyerlin, K.C., Ahluwalia, R.K., Mukundan, R., More, K.L., Borup, R.L., Weber, A.Z., Myers, D.J. and Kusoglu, A. (2021). New roads and challenges for fuel cells in heavy-duty transportation. Nature energy, 6(5), 462-474.[2] Cano, Z. P., Banham, D., Ye, S., Hintennach, A., Lu, J., Fowler, M., & Chen, Z. (2018). Batteries and fuel cells for emerging electric vehicle markets. Nature Energy, 3(4), 279-289.[3] Xiao, L., Chen, J., Wu, Y., Zhang, W., Ye, J., Shao, S., & Xie, J. (2021). Effects of pressure levels in three-cascade storage system on the overall energy consumption in the hydrogen refueling station. International Journal of Hydrogen Energy, 46(61), 31334-31345.[4] Rothuizen, E., Mérida, W., Rokni, M., & Wistoft-Ibsen, M. (2013). Optimization of hydrogen vehicle refueling via dynamic simulation. International journal of hydrogen energy, 38(11), 4221-4231.[5] Rothuizen, E., & Rokni, M. (2014). Optimization of the overall energy consumption in cascade fueling stations for hydrogen vehicles. International journal of hydrogen energy, 39(1), 582-592.

(Invited) Regenerative Fuel Cell System Utilizing a High Differential Pressure Water Electrolysis Technology

The expansion of manned activities in space requires energy system technology that utilizes sunlight, and hydrogen fuel cells are one such means. By electrolyzing water with sunlight, energy is stored with oxygen and hydrogen, and electricity is generated by fuel cells. The generated water can be recycled, and energy can be stored and supplied without external replenishment. This is commonly called a regenerative fuel cell. In the space domain, such energy systems must be compact and lightweight, and gas must be stored under high pressure. However, mechanical compressors that are generally used for compressing are heavy, and there are also issues of vibration and noise.Since the 1990s, Honda has worked on the development of high-differential-pressure water electrolysis technology that generate hydrogen from renewable energy and compress without a mechanical compressor, in parallel with the development of fuel cell technology. High-differential-pressure water electrolysis is a technology that generates high pressure hydrogen by moving the protons generated by electrolysis to the cathode through the Proton exchange membrane (PEM) . The energy required is only the potential generated by the difference in hydrogen concentration, which is superior to small mechanical compressors whose efficiency is reduced by friction loss. However, a large differential pressure is generated across the PEM because only one side is at a high pressure. Honda has achieved a maximum pressure increase of 70 MPa by using its own structure. Moreover, this principle can be applied not only to the generation and pressurization of hydrogen, but also to oxygen. Honda is working on the development of RFC technology that integrates these hydrogen technologies with the aim of applying them not only to sustainability on Earth, but also to the space domain. Currently, we are undertaking a JAXA project and are promoting the production of a breadboard model.The feature of Honda's RFC technology is that it applies high-differential-pressure water electrolysis technology, not only to generate oxygen and hydrogen, but also to pressurize each gas. By not using a mechanical compressor, it is possible to downsize the system, and it is also no vibration or noise. Utilizing the characteristics of this technology, we are planning to build an energy system that can store energy at high density and apply it to various manned missions.Honda's RFC consists of the high-differential-pressure water electrolysis system that simultaneously electrolyzes water and pressurizes oxygen, a Electrochemical hydrogen compressor system (EHC system) that electrochemically pressurizes the hydrogen and a fuel cell system. In the electrolysis stack, oxygen is generated and compressed to the target pressure by the differential pressure water electrolysis. The generated hydrogen is sent to the EHC stack that also applies the technology of high-differential pressure water electrolysis, where the hydrogen is pressurized. As a result, both oxygen and hydrogen gases were generated and compressed without a mechanical compressor. For the fuel cell system, the compact and highly efficient fuel cell technology that has been developed for FCVs is applied. When the fuel cell is used on the ground, oxygen is supplied from the atmosphere, but in space RFC it is necessary to generate electricity using pure oxygen and to circulate the system. A dedicated circulating FC system was constructed to achieve stable power generation. The water produced by power generation is used in the next water electrolysis cycle, and the proof of principle as RFC has been completed. In addition to these basic functions, for space application, we must address issues not found on Earth, such as heat management in a vacuum, radiation, and vibrations during launch. Starting with the lunar exploration mission scheduled for 2030, Honda will develop this technology for the spread of manned activities. Figure 1

Coupled mechanical and electrochemical modeling and simulations for electrochemical hydrogen compressors (EHC)

A three-dimensional (3-D) model of an electrochemical hydrogen compressor (EHC) cell was developed by rigorously accounting for the hydrogen oxidation and evolution reactions and resulting species and charge transport through various EHC components. Particular emphasis was placed on coupling computational fluid dynamics (CFD) and finite element method (FEM) methodology to predict EHC performance numerically under the deformed cell geometries, i.e., induced by the cell assembly and the hydrogen pressure difference between the anode and cathode sides. First, the EHC model was validated experimentally against polarization curves and impedance spectra measured under different hydrogen compression ratios and operating temperatures. In general, the simulation results compared well with the measured data and further revealed the operating characteristics of the EHC cells. In particular, the most irreversible voltage rise comes from the ohmic overpotential because of the proton transport through the membrane, clearly indicating dehydration of the electrolyte due mainly to the electro-osmotic drag effect is one of the most critical issues for efficient EHC operations. While the dehydration issue tends to be mitigated under higher hydrogen discharge pressure or higher operating temperatures, the cell deformation toward the low-pressure side (anode) is visible even with the low hydrogen compression ratio of 10, clearly requiring improvement in the mechanical properties of EHC components and cell structure for a higher compression of hydrogen gas.

Performance analysis of a gas-to-power system based on protonic-ceramic electrochemical compressor

In this study, two scenarios are considered to evaluate the performance of a protonic ceramic electrochemical hydrogen compressor (EHC) and reformer integrated with a proton exchange membrane fuel cell (PEMFC). First scenario includes integration of an EHC with PEMFC and in the second scenario, steam methane reforming (SMR) is replaced by an EHC. Results show that the highest energy and exergy efficiencies of the system in the first scenario is achieved when the area-specific resistance (ASR) in EHC is 1.5 Ωcm2. An increase in the working temperature of EHC causes a considerable rise in the exergy destruction and an increase of energy efficiency by 7% in the first scenario, while the temperature of the reformer affects the exergy destruction, negligibly. The parametric study indicates that the best value of the current density of PEMFC is 0.8481 A/cm2 and 0.8324 A/cm2 and the best current density of PEM-EHC value is 0.4468 A/cm2 and 0.11 A/cm2 in the 1st and 2nd scenarios, respectively. Under the same conditions, energy and exergy efficiencies for the first scenario are 61.63% and 54.9% and for the second scenario are 42.48% and 14.61%, respectively.

PEM Electrochemical Hydrogen Compression with Sputtered Pt Catalysts.

This work presents research on thin magnetron-sputtered platinum (Pt) films deposited over commercial gas diffusion electrodes and applied to convert and pressurize hydrogen in an electrochemical hydrogen pump. The electrodes were integrated into a membrane electrode assembly with a proton conductive membrane. Their electrocatalytic efficiency toward hydrogen oxidation and hydrogen evolution reactions was studied in a self-made laboratory test cell by means of steady-state polarization curves and cell voltage measurements (U/j and U/pdiff characteristics). The achieved current density at a cell voltage of 0.5 V, the atmospheric pressure of the input hydrogen, and a temperature of 60 °C was more than 1.3 A cm-2. The registered increase in the cell voltage with the increasing pressure was only 0.05 mV bar-1. Comparative data with commercial E-TEK electrodes reveal the superior catalyst performance and essential cost reduction of the electrochemical hydrogen conversion on the sputtered Pt films.

Thermodynamics, Transport, and Kinetics in BaZr0.8Y0.2O3−δ Electrolytes and their Impact on Hydrogen Separation and Compression

This paper initially fits a comprehensive set of thermodynamic and transport properties charged mobile defects (protons, oxygen vacancies, and small polarons) in proton-conducting BaZr0.8Y0.2O3−δ (BZY20). The fits are based on recently published measurements, including conductivity, proton concentrations via Karl–Fischer titration, and non-stoichiometry via thermogravimetric analysis, all with wide ranges of temperatures and pressures. These properties are needed for inclusion in physics-based models. The paper goes on to fit charge-transfer kinetics in Butler–Volmer form, based primarily in protonic-ceramic fuel cell data in button-cell format. These fits use the previously fitted thermodynamic and transport properties without alteration. The next step is to consider the kinetics of H2O-incorporation kinetics (i.e. Stotz-Wagner hydration). Unfortunately, to date, there are no direct measurements of these thermal (i.e. not charge-transfer) kinetics. However, the present analysis shows great sensitivities to the defect-incorporation kinetics, ranging from near equilibration to strong rate limitations. The paper concludes with modeling and interpreting the performance of an electrochemical hydrogen-compression cell, using the newly established properties.

Minimizing Area-Specific Resistance of Electrochemical Hydrogen Compressor under Various Operating Conditions Using Unsteady 3D Single-Channel Model.

Extensive research has been conducted over the past few decades on carbon-free hydrogen energy. Hydrogen, being an abundant energy source, requires high-pressure compression for storage and transportation due to its low volumetric density. Mechanical and electrochemical compression are two common methods used to compress hydrogen under high pressure. Mechanical compressors can potentially cause contamination due to the lubricating oil when compressing hydrogen, whereas electrochemical hydrogen compressors (EHCs) can produce high-purity, high-pressure hydrogen without any moving parts. A study was conducted using a 3D single-channel EHC model focusing on the water content and area-specific resistance of the membrane under various temperature, relative humidity, and gas diffusion layer (GDL) porosity conditions. Numerical analysis demonstrated that the higher the operating temperature, the higher the water content in the membrane. This is because the saturation vapor pressure increases with higher temperatures. When dry hydrogen is supplied to a sufficiently humidified membrane, the actual water vapor pressure decreases, leading to an increase in the membrane's area-specific resistance. Furthermore, with a low GDL porosity, the viscous resistance increases, hindering the smooth supply of humidified hydrogen to the membrane. Through a transient analysis of an EHC, favorable operating conditions for rapidly hydrating membranes were identified.

Experimental and modeling studies of a high-temperature electrochemical hydrogen compressor

Some non-technical factors such as economics and logistics prevent hydrogen (H2) technologies from becoming more widespread in daily life. Today, the prevalence of H2 technologies requires new technological developments. Electrochemical hydrogen compressors (ECHC) are of great interest due to their ability to pressurize and purify in one step. In this study, the electrochemical H2 compression performance of high phosphoric acid (PA) doped poly 2,2-m-phenylene-5,5-benzimidazole (PBI) membrane-based HT-ECHC under high temperature and non-humid conditions was investigated through both an experimental and a numerical approach. The H2 compression capacity of HT-ECHC at different operating voltages was examined by performance tests at 160 °C, and it was determined that the electrochemical compression performance increased with increasing operating voltage. It was observed that the current density values also increased with increasing voltage, and it was determined that a current density of 61.2 A was obtained at 1 V. As a result of the tests, H2 was successfully compressed from atmospheric pressure to 60 bar by HT-ECHC without any gas leakage. The results of the developed model were compared with the experimental performance test data, and the variation of molar flow, cell voltage, and cell efficiency over time was examined. It has been determined that the back diffusion from the cathode to the anode in the cell increases with the increasing operating voltage of HT-ECHC and therefore the cell efficiency decreases. It has been evaluated that the developed model and experimental results are in good agreement.

Preliminary Study for the Commercialization of a Electrochemical Hydrogen Compressor

A global energy shift to a carbon-neutral society requires clean energy. Hydrogen can accelerate the process of expanding clean and renewable energy sources. However, conventional hydrogen compression and storage technology still suffers from inefficiencies, high costs, and safety concerns. An electrochemical hydrogen compressor (EHC) is a device similar in structure to a water electrolyzer. Its most significant advantage is that it can accomplish hydrogen separation and compression at the same time. With no mechanical motion and low energy consumption, the EHC is the key to future hydrogen compression and purification technology breakthroughs. In this study, the compression performance, efficiency, and other related parameters of EHC are investigated through experiments and simulation calculations. The experimental results show that under the same experimental conditions, increasing the supply voltage and the pressure in the anode chamber can improve the reaction rate of EHC and balance the pressure difference between the cathode and anode. The presence of residual air in the anode can impede the interaction between hydrogen and the catalyst, as well as the proton exchange membrane (PEM), resulting in a decrease in performance. In addition, it was found that a single EHC has a better compression ratio and reaction rate than a double EHC. The experimental results were compatible with the theoretical calculations within less than a 7% deviation. Finally, the conditions required to reach commercialization were evaluated using the theoretical model.

The role of the EHC system in the transition to a sustainable energy future: A review

The hydrogen economy is seen as the key point for the transition to a sustainable energy future. Since hydrogen has a very low volumetric energy density, in order to be used as an energy carrier, it must be compressed and transported. Various methods used in the compression of hydrogen have been mentioned in the literature. Among these proposed methods, the electrochemical hydrogen compressor system (EHC), which has the ability to pressurize hydrogen as well as purify it, stands out as a promising technology due to its economic and environmental friendly nature. In this article, focusing on this prominent technology, first of all, the characteristics of the basic methods used in the purification and compression of hydrogen are reviewed. The EHC system, on the other hand, was handled comprehensively, the components of the system, the design, the working principle, and the parameters affecting its performance were analyzed, the research made in this field was presented and the missing aspects of the system were mentioned. Finally, the commercial applications of the existing EHC system were also included, current developments were evaluated, and the necessity of the system for the hydrogen value chain was outlined.

Recent advances and perspectives in diagnostics and degradation of electrochemical hydrogen compressors

This paper presents a literature overview of progress and current state-of-the-art electrochemical hydrogen compressors (EHCs) emphasizing their performance diagnostics, durability testing methods, and possible degradation mechanisms that could affect the desired performance. The review also critically gives current technology shortcomings and challenges, primarily considering the current testing procedures issues of EHC state-of-health, but also suggests potential development ideas for improvements in perspective.

Enhanced electrochemical hydrogen compression performance with a gradient water-retaining hybrid membrane

Stored hydrogen has become increasingly important as an efficient and clean energy source. Noiseless and highly efficient electrochemical hydrogen compressors (EHCs) have been employed in H2 fueling stations, refrigeration, and hydrogen purification. However, unequal water distribution in EHCs during operation significantly affects the compression performance. Herein, we developed a gradient hybrid membrane (PFSA/PCTS-5 + 2.5 + 1 %) for use in EHCs by synthesizing phosphorylated chitosan (PCTS) using chitosan, 2-phosphonate butane-1, 2, 4-tricarboxylic acid, and other water-retaining components. Advanced physical characterizations were employed to analyze the morphology, chemical structure, proton conductivity, water uptake ratio, hydrophilicity, thermal stability, and mechanical properties of the membranes. Furthermore, the membrane electrode assemblies (MEAs) fabricated with PFSA/PCTS hybrid membranes exhibited significant performance enhancement at a 50 % RH. The PFSA/PCTS-5 + 2.5 + 1 %-based MEA yields an EHC that can compress H2 up to 0.9 MPa in 419 s (at 50 % RH) and up to 1.0 MPa in 137 s (at 100 % RH) in compression testing. EIS analysis reveals that the ohmic resistance decreased markedly due to gradient hybrid structure of membrane. Such a remarkable performance is attributed to the gradient structure, high hydrophilicity of the functional groups (–OH, –NH2), and good proton conductivity arising from the synergetic effect of phosphate groups and carboxyl groups.

Minimizing Specific Energy Consumption of Electrochemical Hydrogen Compressor at Various Operating Conditions Using Pseudo-2D Model Simulation.

With the increased usage of hydrocarbon-based fossil fuels, air pollution and global warming have accelerated. To solve this problem, renewable energy, such as hydrogen technology, has gained global attention. Hydrogen has a low volumetric density and thus requires compression technologies at high pressures to reduce storage and transportation costs. Techniques for compressing hydrogen include using mechanical and electrochemical hydrogen compressors. Mechanical compressors require higher specific energy consumption than electrochemical hydrogen compressors. Here, we used an electrochemical hydrogen compressor as a pseudo-two-dimensional model focused on electroosmotic drag, water back-diffusion, and hydrogen crossover flux at various temperatures, polymer electrolyte membrane thicknesses, and relative humidity conditions. To date, there have been few studies based on various operating conditions to find the optimal conditions. This study was conducted to determine the optimal parameters under various operating conditions. A numerical analysis demonstrated that the specific energy consumption was low in a specific current density section when the temperature was decreased. At the above-mentioned current density, the specific energy consumption decreased as the temperature increased. The polymer electrolyte membrane thickness yielded similar results. However, according to the relative humidity, it was confirmed that the higher the relative humidity, the lower the specific energy consumption in all of the current density sections. Therefore, when comparing temperatures of 30 °C and 80 °C at 145 A/m2, operating at 30 °C reduces the specific energy consumption by 12.12%. At 3000 A/m2 and 80 °C, the specific energy consumption is reduced by 11.7% compared to operating at 30 °C. Using N117 compared to N211 at 610 A/m2 for polymer electrolyte membranes can reduce specific energy consumption by 10.4%. Using N211 in the 1500 A/m2 condition reduces the specific energy demand by 9.6% compared to N117.