Electrochemical Hydrogen Compression Research Articles

Insights into electrochemical hydrogen compressor operating parameters and membrane electrode assembly degradation mechanisms

Understanding how to control the different operating parameters in an electrochemical hydrogen compressor can provide a basis for further improving its performance. In this paper, the effects of hydrogen stoichiometric ratio:1.0–2.0, input temperature: 30–90 °C, inlet pressure: 30–90 kPa were systematically analyzed. Besides, we evaluate and discuss how various operating parameters and current densities affect the running performance, charge transfer, mass transfer, and kinetics of the hydrogen electrode reaction, using I–V curves and electrochemical impedance spectroscopy. Time and energy consumption are recorded at different voltages during the hydrogen compression process. For different actual needs, it is determined that 0.3 V is the best choice for a compression ratio of up to 22 in this system. We also analyze the causes and mechanisms of membrane electrode assembly deterioration and suggest improvements in the compression process and operation strategy.

Phosphoric Acid-Doped Biphenyl-Backbone Ion-Pair Coordinated Pems with Broad Relative Humidity Tolerance

Fuel cell has been recognized as a promising electrochemical device attributed to its high energy efficiency and zero CO2 emission. As an essential component of fuel cell, currently the most widely used proton exchange membrane (PEM), Nafion®, operates only at low temperature (<100 ˚C) and high relative humidity (>80% RH). Although phosphoric acid (PA)-doped polybenzimidazole membranes have been reported to offer good proton conductivity at temperatures 140–180 ˚C, they suffer from severe performance degradation due to acid leaching when moisture is present. For wider adoption of PEM fuel cell technology, the development of PEM that is capable of working over a broad operating condition window is highly desirable. In this presentation, three PA-doped biphenyl-backbone ion-pair coordinated PEMs with different quaternary ammonium structures (alkyltrimethylammonium, piperidinium, and 1,2-dimethylimidazolium) were reported. The resulting PA-doped PEMs were comprehensively characterized in terms of PA doping level, proton conductivity, RH tolerance, thermal stability, and mechanical properties. Acid titration result indicates the PA doping levels of three membrane samples were between six and eight, and the size and structure of cation groups of the ion-pair polymers were found to affect their PA doping levels. Proton conductivity was studied as a function of RH over a wide range of 5% to 95% RH. Stable conductivity was observed up to 70% RH at 80 ˚C for 10 h. A combination of high proton conductivity at low RH conditions and good humidity tolerance makes this new class of PEMs great potential candidates for use in electrochemical devices such as PEM fuel cell and electrochemical hydrogen compressor.

Poison mitigation strategies for the use of impure hydrogen in electrochemical hydrogen pumps and fuel cells

A new approach to mitigate against common poisons present in hydrogen for electrochemical hydrogen compressors and fuel cells is introduced. This approach uses the inclusion of ozone in the oxygen bleed as a poison mitigation strategy (online cleaning). This ozone treatment is also used to recover systems which have already been degraded by exposure to poisons (offline treatment). The different poisons studied are representative of products from a steam methane reformer (SMR), hydrogen contaminated by H2S, and an SMR feed contaminated with H2S. The efficacy of the cleaning methodology on the performance of an electrochemical hydrogen pump (EHP) and polymer electrolyte fuel cell are evaluated by comparing to the performance achieved when using pure hydrogen. Gas compositions containing ozone were more effective than O2 alone in cleaning poisons such as COad and Sad from the Pt and PtRu catalysts, thus, increasing the current densities and efficiencies of the EHP and polymer fuel cell. For the more severely poisoned streams, inclusion of ozone doubles the achievable current density. The mechanisms of catalyst regeneration using O2 and O2/O3 bleeds, following COad and Sad poisoning, involved both electrochemical and heterogeneous oxidation.

Techno-economic evaluation on a hybrid technology for low hydrogen concentration separation and purification from natural gas grid

Hydrogen can be stored and distributed by injecting into existing natural grids, then, at the user site separated and used in different applications. The conventional technology for hydrogen separation is pressure swing adsorption (PSA). The recent NREL study showed the extraction cost for separating hydrogen from a 10% H2 stream with a recovery of 80% is around 3.3–8.3 US$/kg. In this document, new system configurations for low hydrogen concentration separation from the natural gas grid by combining novel membrane-based hybrid technologies will be described in detail. The focus of the manuscript will be on the description of different configurations for the direct hydrogen separation, which comprises a membrane module, a vacuum pump and an electrochemical hydrogen compressor. These technological combinations bring substantial synergy effect of one-another while improving the total hydrogen recovery, purity and total cost of hydrogen. Simulation has been carried out for 17 different configurations; according to the results, a configuration of two-stage membrane modules (in series) with a vacuum pump and an electrochemical hydrogen compressor (EHC) shows highest hydrogen purity (99.9997%) for 25 kg/day of hydrogen production for low-pressure grid. However, this configuration shows a higher electric consumption (configuration B) due to the additional mechanical compressor between the two-stage membrane modules and the EHC. Whereas, when the compressor is excluded, and a double skin Pd membrane (PdDS) module is used in a single-stage while connected to a vacuum pump (configuration A5), the hydrogen purity (99.92%) slightly decreases yet the power consumption considerably improves (1.53 times lower). Besides to these two complementary configurations, the combination of a single membrane module, a vacuum pump and the electrochemical compressor has been also carried out (configuration A) and results show that relatively higher purity can be achieved. Based on four master configurations, this document presents a different novel hybrid system by integrating two to three technologies for hydrogen purification combined in a way that enhances the strengths of each of them.

Parametric study of a proton exchange membrane compressor for electrochemical hydrogen storage using numerical assessment

Abstract This paper investigates a single cell proton exchange membrane based electrochemical hydrogen compressor for hydrogen storage purposes. This work applies a three-dimensional numerical model based on single-domain method in order to simulate the thermal and electrochemical kinetics of the electrochemical cell. The design parameters including operating temperature, pressure, the thickness and porosity of the gas diffusion layer, and channel dimension affect the electrochemical hydrogen compression cell performance. The results show that the performance of the cell improves by increasing the operating temperature at high current density, but it has a negligible effect within the activation region. Increase of pressure from 1 bar to 20 bar at the current density of 5000 A m−2 reduces the overall cell voltage by almost 24% and the cell performance deteriorates. The results indicate that increase of gas diffusion layer thickness from 0.2 to 0.5 mm has a negative effect on the performance of electrochemical cell. Moreover, a comparison between different gas diffusion layer porosities shows no significant effect on the polarization curve due to the high permeability of hydrogen. Furthermore, the required voltage will be grown in the range of 87.84 -70.61 mV by varying the channel rib in the range of 0.5 -1 mm.

Using of an Electrochemical Compressor for Hydrogen Recirculation in Fuel Cell Vehicles

AbstractThe automotive industry sees hydrogen‐powered fuel cell (FC) drives as a promising option with a high range and short refueling time. Current research aims to increase the profitability of the fuel cell system by reducing hydrogen consumption. This study suggests the use of an electrochemical hydrogen compressor (EHC) for hydrogen recirculation. Compared to mechanical compressors, the EHC is very efficient due to the almost isothermal conditions and due to its modular structure, can only take up a minimal amount of space in vehicles. In addition, gas separation and purification of the hydrogen takes place in an EHC, which is a significant advantage over the standard recirculation with a blower or a jet pump. The high purity of the hydrogen at the cathode outlet of the EHC, also increased partial pressure of the hydrogen at the fuel cell inlet and its efficiency. The study carried out shows that replacing the blower with the EHC reduces the hydrogen loss by purging by up to ∼95% and the efficiency of the FC system could be further improved. Thus, the EHC has a great potential for recycling hydrogen in FC systems in the automotive industry and is a great alternative to the current blower.

Phosphoric Acid-Doped Ion-Pair Coordinated PEMs with Broad Relative Humidity Tolerance

Proton exchange membrane (PEM) capable of working over a broad operating condition window is critical for successful adoption of PEM-based electrochemical devices. In this work, phosphoric acid (PA)-doped biphenyl-backbone ion-pair coordinated PEMs were prepared by quaternization of BPBr-100, a precursor polymer, with three different tertiary amines including trimethylamine, 1-methylpiperidine, and 1,2-dimethylimidazole followed by membrane casting, ion exchange reaction to hydroxide ion, and doping with PA. The resulting PA-doped ion-pair PEMs were characterized in terms of PA doping level, proton conductivity, relative humidity (RH) tolerance, thermal stability, and mechanical properties. PA doping levels were between six and eight according to acid-base titration. The size and structure of the cation group of ion-pair polymers were found to affect the PA doping level and water uptake. Proton conductivity was studied as a function of RH over a wide range of 5% to 95% RH. Stable conductivity at 80 °C was observed up to 70% RH for 10 h. Mechanical property characterization indicates that the PA doping process resulted in more ductile membranes with significantly increased elongation at break due to the plasticization effect of PA. A combination of high proton conductivity at low RH conditions, and good humidity tolerance makes this new class of PEMs great potential candidates for use in electrochemical devices such as proton exchange membrane fuel cells and electrochemical hydrogen compressors.

Effect of back-diffusion on the performance of an electrochemical hydrogen compressor

Hydrogen offers the potential to decarbonize the automotive and stationary power sectors and is therefore expected to play an increasingly significant role in meeting global energy demand. However, due to its low volumetric and gravimetric energy densities, it is important to find methods to efficiently store hydrogen in order to grow the hydrogen economy. Storing hydrogen as a compressed gas could be achieved by electrochemical compression (ECC), which is a membrane-based alternative to conventional mechanical compressors. ECC can be superior to mechanical compressors because of its higher efficiency, lack of moving parts and noiseless operation. Here, we report on the ECC of hydrogen using a Nafion 115 membrane at room temperature. Pressure vs. time curves have been collected at various operating voltages, and a compression ratio of 150 has been achieved with a single cell at an operating voltage of 0.1 V. This work focuses on the loss in electrochemical compression efficiency due to back-diffusion. A theoretical formulation for the ECC process incorporating back-diffusion is proposed and validated by experiments. A robust definition for ECC efficiency that properly accounts for back diffusion is also proposed.

Performance analysis and exergoeconomic assessment of a proton exchange membrane compressor for electrochemical hydrogen storage

Electrochemical hydrogen compression (EHC) is a promising alternative to conventional compressors for hydrogen storage at high pressure, because it has a simple structure, low cost of hydrogen delivery, and high efficiency. In this study, the performance of an EHC is evaluated using a three-dimensional numerical model and finite volume method. The results of numerical analysis for a single cell of EHC are extended to a full stack of EHC. In addition, exergy and exergoeconomic analyses are carried out based on the numerical data. The effects of operating temperature, pressure, and gas diffusion layer (GDL) thickness on the energy and exergy efficiencies and the exergy cost of hydrogen are examined. The motivation of this study is to examine the performance of the EHC at different working conditions and also to determine the exergy cost of hydrogen. The results reveal that the energy and exergy efficiency of EHC stack improve by almost 3.1% when operating temperature increases from 363 K to 393 K and the exergy cost of hydrogen decreases by 0.5% at current density of 5000 A m−2. It is concluded that energy and exergy efficiency of EHC stack decrease by 25% and 5.4% when the cathode pressure increases from 1 bar to 30 bar, respectively. Moreover, it is realized that the GDL thickness has a considerable effect on the EHC performance. The exergy cost of hydrogen decreases by 53% when the GDL thickness decreases from 0.5 mm to 0.2 mm at current density of 5000 A m−2.

Effect of CO2 on the performance of an electrochemical hydrogen compressor

Abstract It is well known that CO2 has a negative effect on the catalyst of the fuel cell causing inhibition in presence of H2-CO2 mixture. According to literature, CO formation is the responsible of catalyst inhibition. Since an electrochemical hydrogen compressor (EHC) has a working principle similar to a fuel cell, the presence of CO2 can also be detrimental for the behavior of the compressor. In this work, the effect of CO2 in binary H2-CO2 mixtures on the performance of an EHC has been investigated in detail. Both Reverse Water Gas Shift (RWGS) and electrochemical reduction of CO2 may occur on the catalyst of an EHC. The main aim of the manuscript is to show RWGS is the most probable cause of catalyst inhibition. For a better understanding of the parameters involved in the catalyst inhibition in presence of a H2-CO2 mixture, different working conditions, viz. voltage and H2 concentration, are applied to the compressor. These experiments show a faster catalyst inhibition for lower H2 concentrations and lower voltages supplied. The temperature also plays an important role on the performance of the compressor. Indeed, since the RWGS is an endothermic reaction, the pollution of the catalyst is faster at higher temperatures. Recovery methods are also evaluated, and it was observed that air bleeding is most convenient because of its effectivity and recovery rate.

Measurement of water permeation through membranes from extremely high hydraulic pressure to atmospheric pressure

The performance of electrochemical hydrogen compressors (EHCs) with polymer electrolyte membranes which work in the presence of water is affected by the flooding; however, the water permeation through the membranes from the high-pressure side (dozens of MPa) to the low-pressure side has never measured. In this study, a method to measure the permeation from the high hydraulic pressure side (2–20 MPa) to the atmospheric pressure side is shown, using EHC cells and a water hydraulic pump. By this method, liquid-liquid permeation (LLP) and liquid-vapor permeation (LVP) were measured. The higher the hydraulic pressure was, the more the water flux was, and the increase in the permeation was large for LLP. It is considered that the electro-osmotic drag accumulates water on the cathode at low pressure during the initial stage of the electrochemical hydrogen compression and then the permeation from the cathode to the anode exceeds the electro-osmotic drag as the cathode pressure increases, which causes the decrease in the performance by flooding.

Feasibility of Hydrogen Compression in an Electrochemical System: Focus on Water Transport Mechanisms

AbstractIn this study, the behavior of an electrochemical hydrogen compressor (EHC) able to compress hydrogen up to 32 bar was investigated. The current density distribution along the EHC was measured using a segmented cell. It was found to decrease from 0.75 A cm−2 to 0.65 A cm−2 along the EHC when using Nafion 117 and when high relative humidity hydrogen was fed to the EHC (at 0.66 A cm−2 and 0.36 V). This drop corresponded to a decrease of the relative humidity of the hydrogen flow from 90 to 55% along the gas channels at the anode side, evidencing the local dehydration of the PEM due to the unbalanced water transport across the membrane. As a consequence, the membrane resistance increased, thus a higher voltage had to be supplied to the EHC in order to maintain good performances, decreasing the overall efficiency. On the other hand, unstable operating conditions were observed when using hydrogen with a low relative humidity.A pseudo‐2D model was developed along with experimental studies to estimate the physical parameters enhancing the efficiency of the EHC. A higher efficiency was obtained when using a thinner membrane than Nafion 117 (53% vs. 37%, at 60 °C and 0.66 A cm−2).

(Invited) Laser 3D Printing of Highly Compacted Protonic Ceramic Electrochemical Cells

Protonic ceramic electrochemical devices (PCEDs) such as fuel cells, electrolysis cells, membrane reactors, and electrochemical hydrogen compressors can operate at low temperatures (300-600oC) because of the low proton transport activation energy, which allows the significant improvement of durability, materials cost, and efficiency of PCEDs. The great effort has been devoted to discovering new component materials for achieving improved cell or stack performance. Parallelly, the manufacturing of the cells and stacks with the desired microstructures should also be paid more attention. In this work, the highly compacted multilayer protonic ceramic fuel cell and electrolysis cell stacks were designed for achieving significant improvement of volumetric power density and substantially decreased the device size, which will be fabricated by a novel laser 3D printing technique. The crack-free layers of dense protonic ceramic electrolyte, dense interconnect, porous hydrogen electrode and porous oxygen electrode were 3D printed and laser sintered, which showed desired microstructures and promising electrochemical properties. The five-layer single cells comprised of two porous electrodes, one dense electrolyte, and two interconnect layers were automatically manufactured through laser 3D printing. The single cells demonstrated promising fuel cell and water electrolysis performance at 600oC.

Solubility of Water in Hydrogen at High Pressures: A Molecular Simulation Study

Hydrogen is one of the most popular alternatives for energy storage. Because of its low volumetric energy density, hydrogen should be compressed for practical storage and transportation purposes. Recently, electrochemical hydrogen compressors (EHCs) have been developed that are capable of compressing hydrogen up to P = 1000 bar, and have the potential of reducing compression costs to 3 kWh/kg. As EHC compressed hydrogen is saturated with water, the maximum water content in gaseous hydrogen should meet the fuel requirements issued by the International Organization for Standardization (ISO) when refuelling fuel cell electric vehicles. The ISO 14687-2:2012 standard has limited the water concentration in hydrogen gas to 5 μmol water per mol hydrogen fuel mixture. Knowledge on the vapor liquid equilibrium of H2O-H2 mixtures is crucial for designing a method to remove H2O from compressed H2. To the best of our knowledge, the only experimental high pressure data (P > 300 bar) for the H2O-H2 phase coexistence is from 1927 [J. Am. Chem. Soc., 1927, 49, 65-78]. In this paper, we have used molecular simulation and thermodynamic modeling to study the phase coexistence of the H2O-H2 system for temperatures between T = 283 K and T = 423 K and pressures between P = 10 bar and P = 1000 bar. It is shown that the Peng-Robinson equation of state and the Soave Redlich-Kwong equation of state with van der Waals mixing rules fail to accurately predict the equilibrium coexistence compositions of the liquid and gas phase, with or without fitted binary interaction parameters. We have shown that the solubility of water in compressed hydrogen is adequately predicted using force-field-based molecular simulations. The modeling of phase coexistence of H2O-H2 mixtures will be improved by using polarizable models for water. In the Supporting Information, we present a detailed overview of available experimental vapor-liquid equilibrium and solubility data for the H2O-H2 system at high pressures.

Thermodynamic Insights for Electrochemical Hydrogen Compression with Proton-Conducting Membranes.

Membrane electrode assemblies (MEA) based on proton-conducting electrolyte membranes offer opportunities for the electrochemical compression of hydrogen. Mechanical hydrogen compression, which is more-mature technology, can suffer from low reliability, noise, and maintenance costs. Proton-conducting electrolyte membranes may be polymers (e.g., Nafion) or protonic-ceramics (e.g., yttrium-doped barium zirconates). Using a thermodynamics-based analysis, the paper explores technology implications for these two membrane types. The operating temperature has a dominant influence on the technology, with polymers needing low-temperature and protonic-ceramics needing elevated temperatures. Polymer membranes usually require pure hydrogen feed streams, but can compress H efficiently. Reactors based on protonic-ceramics can effectively integrate steam reforming, hydrogen separation, and electrochemical compression. However, because of the high temperature (e.g., 600 C) needed to enable viable proton conductivity, the efficiency of protonic-ceramic compression is significantly lower than that of polymer-membrane compression. The thermodynamics analysis suggests significant benefits associated with systems that combine protonic-ceramic reactors to reform fuels and deliver lightly compressed H (e.g., 5 bar) to an electrochemical compressor using a polymer electrolyte to compress to very high pressure.

Second use or recycling of hydrogen waste gas from the semiconductor industry - Economic analysis and technical demonstration of possible pathways

Hydrogen is used as a carrier gas in the photovoltaics and semiconductor industry. Once scrubbed from poisonous and environmentally harmful substances, the hydrogen-rich waste gas streams are released into the atmosphere. This paper presents an economic analysis of different options for further use of these streams. Combustion in a gas engine with attached electricity generation is currently the most technologically proven and economically profitable solution. With the future rise of the hydrogen electric vehicle infrastructure, power generation via a polymer electrolyte membrane (PEM) fuel cell system could become economically feasible at electricity prices of 0.11 €/kWh and higher. Fuel cells are high tech and modular but still relatively expensive today. Another promising technology identified is the recycling of hydrogen via electrochemical hydrogen compression (EHC). EHC is already economically feasible today at a hydrogen price of 11 €/kg or higher. It will become even more profitable with falling membrane electrode assembly prices.

Experimental and modelling study of an electrochemical hydrogen compressor

The energy world is changing rapidly pushed also by the need for new green energy sources to reduce greenhouse gas emissions. The fast development of renewable energies has created many problems associated with grid management and stability, which could be solved with storage systems. The hydrogen economy could be an answer to the need of storage systems and clean fuel for transportation. The Electrochemical Hydrogen Compressor (EHC) is an electrochemical device, which could find a place in this scenario giving a solution for the hydrogen purification and compression for storage. This work analyzes, through experimental and modeling studies, the performance of the EHC in terms of polarization curve, Hydrogen Recovery Factor (HRF) and outlet hydrogen purity. The influence of many input parameters, such as the total inlet flow rate, the hydrogen inlet concentration, the contaminant in the feed, and the cathode pressure have been investigated. Furthermore, the EHC performance have been modelled in a 1D + 1D model implemented in Matlab® solving the Butler-Volmer system of equations numerically. The experimental campaign has shown that high purities can be obtained for the hydrogen separation from N2 and CH4 and purities over 98% feeding He. An increase in the cathode pressure has shown a slight improvement in the obtained purity. A comparison between PSA unit and EHC for a mixture 75% H2 – 25% CH4 at different outlet hydrogen pressure and purity was performed to analyze the energy consumption required. Results show PSA unit is convenient at large scale and high H2 concentration, while for low concentration is extremely energy intense. The EHC proved to be worthwhile at small scale and higher outlet hydrogen pressure.

Membrane based purification of hydrogen system (MEMPHYS)

A hydrogen purification system based on the technology of the electrochemical hydrogen compression and purification is introduced. This system is developed within the scope of the project MEMPHYS. Therefore, the project, its targets and the different work stages are presented. The technology of the electrochemical purification and the state of the art of hydrogen purification are described. Early measurements in the project have been carried out and the results are shown and discussed. The ability of the technology to recover hydrogen from a gas mixture can be recognized and an outlook into further optimizations shows the future potential. A big advantage is the simultaneous compression of the purified hydrogen up to 200 bar, therefore facilitating the transportation and storage.

Nanocomposite membrane based on SPEEK as a perspectives application in electrochemical hydrogen compressor

Achieving favourable proton exchange membrane characteristics such as proton conduction, mechanical properties and hydrogen crossover is one of the main challenges in development of Electrochemical Hydrogen Compressor (EHC) systems for improving energy consumption. This work demonstrates three different in-house fabricated membranes based on Sulphonated poly (ether-ether ketone, SPEEK). The first membrane is an unmodified membrane ([S70]), second membrane ([S70/HNT15], 15 % wt/wt) was modified with a nanoclay (Halloysite Nanotubes, HNT), and last membrane is Halloysite nanotubes impregnated with Phosphotungstic Acid ([S70/(PWA/HNT30)15]). These membranes show different hydrogen crossover rate, with the [S70] membrane exhibiting 3.873 × 10−08 mol bar−1s−1cm−2 whereas the [S70/HNT15] and [S70/(PWA/HNT30)15] nanocomposite membranes show rates of 7.296 × 10−10 and 9.103 × 10−10 mol bar−1 s−1 cm−2, respectively. Furthermore, unmodified membrane presented quadratic behaviours with increased pressure in cathodic compartment, whereas nanocomposite membranes exhibit a logarithmic behaviour. For another hand, extrapolation data show that unconventional nanocomposites membranes present a low energy consumption at high pressures, which is promising for potential candidates for use in EHC systems.

Evaluation of a Novel Bio-oil Hydrotreating Process Integrating Electrochemical H2 Compression

In fossil-based refinery and biorefinery applications hydrogen is recovered by pressure swing adsorption and subsequently re-pressurized using mechanical compressors. Electrochemical hydrogen compression is an efficient way of separating and compressing H2 from a gaseous mixture within a compact device. In this work, a preliminary investigation of the integration of a bio-oil hydroprocessing unit with a complete novel gas polishing and separation unit was conducted. Apart from the electrochemical compressor, this includes a CO methanation reactor and a ZnO bed to remove the contained CO and H2S impurities of the hydroprocessing reactor outlet and safeguard the trouble-free operation of the electrochemical device. This first assessment revealed that several operating parameters such as the hydrotreating pressure, the gas polishing and separation temperature and the hydrogen recycling ratio limit the possible operating modes of the subsequent units.