High-pressure Hydrogen Production Research Articles

High-pressure Hydrogen Production by Formic Acid Dehydrogenation

High-pressure Hydrogen Production by Formic Acid Dehydrogenation

Decoupled Water Splitting for Green Hydrogen Production: Reshaping Water Electrolysis

Green hydrogen production at scale is essential to fight global warming and climate change. The present water electrolysis technologies present significant barriers to meet this challenge, due to high system and operational costs that emerge from the need to divide each cell into gas-tight cathodic and anodic compartments to avoid mixing hydrogen with oxygen, and from intrinsic energy losses in the complex oxygen evolution reaction. Recent efforts to overcome these barriers include transformative approaches to decouple the hydrogen and oxygen evolution reactions using soluble redox couples or solid redox electrodes that mediate the ion exchange between the primary electrodes such that hydrogen and oxygen are generated at different times and/or different cells. This leads the way to membraneless electrolyzer architectures that can enhance safety, reduce system costs, and provide operational advantages such as high-pressure hydrogen production. In particular, E-TAC water slitting offers these advantages as well as ultrahigh efficiency and compact design of rolled electrode assemblies, opening new frontiers for advanced water electrolysis.

Experimental investigation on shock wave propagation and self-ignition of pressurized hydrogen in different three-way tubes

This paper experimental investigated the shock wave propagation characteristics and self-ignition produced by the high-pressure hydrogen release in the three-way tubes. Two Y-shaped tubes (60°, 120°) and one T-shaped tube (180°) were used in the experiments and the initial release pressure was 3–8 MPa. The pressure and photoelectric signals in tubes were recorded by the sensor. The results showed that the intensity of shock wave was enhanced or attenuated during the entire releasing process, but the dominant effect was distinct under different conditions and the two effects synergistically affected the occurrence possibility of self-ignition. The critical release pressure for self-ignition in the three-way tubes decreased with the increasing of the bifurcation angle, and the most difficult to occur the self-ignition was the 60° Y-tube in this study. In addition, quenching occurred in the 60° Y-tube when the initial release pressure was 6 MPa, because the temperature of the mixture dropped by the expansion effect. Furthermore, the intensity of the reflected shock wave was not strong enough to promote hydrogen rekindled. This experimental results have reference value for the safety of high-pressure hydrogen production, storage and transportation, and are helpful to understand the influence of bifurcation structure on self-ignition in energy application.

Catalyst-coated proton exchange membrane for hydrogen production with high pressure water electrolysis

Green hydrogen is currently enjoying a worldwide momentum due to its potential in supporting the United Nations Sustainable Development Goals. It is one of key technologies toward the establishment of a global low-carbon energy infrastructure. As a viable solution to achieve green hydrogen from renewable sources such as wind and solar powers, the process of proton exchange membrane (PEM) water electrolysis enables scalable stacked devices and systems for high pressure hydrogen production. By developing a catalyst-coated proton exchange membrane, we constructed membrane electrode assemblies (MEAs) and assembled them into a five-cell stack device to optimize the materials and components. After device characterization and optimization, a 20 kW PEM water electrolysis system was built, which, under high pressure operating conditions, exhibited favorable hydrogen production performance with 82.9% energy efficiency at the current density of 1000 mA/cm2 and reaction temperature of 70 °C. The resulting hydrogen production rate of the system with catalyst-coated membranes reached 3.09 N m3/h, while the power consumption for hydrogen production was 4.39 kWh/N m3. The results indicate the feasibility of PEM water electrolysis technology for green hydrogen production, for which we envision development into commercial applications in the near future.

Faraday’s Efficiency Modeling of a Proton Exchange Membrane Electrolyzer Based on Experimental Data

In electrolyzers, Faraday’s efficiency is a relevant parameter to assess the amount of hydrogen generated according to the input energy and energy efficiency. Faraday’s efficiency expresses the faradaic losses due to the gas crossover current. The thickness of the membrane and operating conditions (i.e., temperature, gas pressure) may affect the Faraday’s efficiency. The developed models in the literature are mainly focused on alkaline electrolyzers and based on the current and temperature change. However, the modeling of the effect of gas pressure on Faraday’s efficiency remains a major concern. In proton exchange membrane (PEM) electrolyzers, the thickness of the used membranes is very thin, enabling decreasing ohmic losses and the membrane to operate at high pressure because of its high mechanical resistance. Nowadays, high-pressure hydrogen production is mandatory to make its storage easier and to avoid the use of an external compressor. However, when increasing the hydrogen pressure, the hydrogen crossover currents rise, particularly at low current densities. Therefore, faradaic losses due to the hydrogen crossover increase. In this article, experiments are performed on a commercial PEM electrolyzer to investigate Faraday’s efficiency based on the current and hydrogen pressure change. The obtained results have allowed modeling the effects of Faraday’s efficiency by a simple empirical model valid for the studied PEM electrolyzer stack. The comparison between the experiments and the model shows very good accuracy in replicating Faraday’s efficiency.

High-pressure hydrogen production with inherent sequestration of a pure carbon dioxide stream via fixed bed chemical looping

The proof of concept for the production of pure pressurized hydrogen from hydrocarbons in combination with the sequestration of a pure stream of carbon dioxide with the reformer steam iron cycle is presented. The iron oxide based oxygen carrier (95% Fe2O3, 5% Al2O3) is reduced with syngas and oxidized with steam at 1023 K. The carbon dioxide separation is achieved via partial reduction of the oxygen carrier from Fe2O3 to Fe3O4 yielding thermodynamically to a product gas only containing CO2 and H2O. By the subsequent condensation of steam, pure CO2 is sequestrated. After each steam oxidation phase, an air oxidation was applied to restore the oxygen carrier to hematite level. Product gas pressures of up to 30.1 bar and hydrogen purities exceeding 99% were achieved via steam oxidations. The main impurities in the product gas are carbon monoxide and carbon dioxide, which originate from solid carbon depositions or from stored carbonaceous molecules inside the pores of the contact mass. The oxygen carrier samples were characterized using elemental analysis, BET surface area measurement, XRD powder diffraction, SEM and light microscopy. The maximum pressure of 95 bar was demonstrated for hydrogen production in the steam oxidation phase after the full oxygen carrier reduction, significantly reducing the energy demand for compressors in mobility applications.

Iridium substitution in nickel cobaltite renders high mass specific OER activity and durability in acidic media

Oxygen evolution reactions being kinetically sluggish and highly expensive remains bottleneck in high pressure hydrogen production from acidic solution water electrolysis. Process economization is mostly affected due to larger consumption of precious iridium as an anodic catalyst. Therefore, effective utilization of noble metal remains a major challenge to be overwhelmed. Comprehensive theoretical and experimental studies show electronic dependency on different structural motifs of IrOx. However, due to lack of suitable non-noble host structures for iridium substitution there is hindrance in implementation. In current study, we explored inverse spinel, nickel cobaltite, as a host structure that provides OER beneficial structural motif to iridium sites on account of relatively higher IrO6 edge sharing than in rutile IrO2. Compact presence of octahedras in host structure reduces IrIr bond length for neighboring IrO6 octahedral units in it that further intrinsically improves the iridium sites due to electronic modulations. Specifically, composite comprising 20 mol% iridium in NiCo2-xO4 rendered acid stable 15 folds enhancement in mass specific OER activity relative to IrO2 resulting in substantial reduction of iridium content. Fabricated composite displayed an onset potential and tafel slope of 1.425 V and 40.4 mV dec−1, respectively in relative to 1.475 V and 68.1 mV dec−1 for pure IrO2. Current approach for effectively utilizing precious metal will lead in future for economizing hydrogen production via water splitting.

Exergetic sustainability indicators for a high pressure hydrogen production and storage system

This study examines the exergetic sustainability effect of PEM electrolyzer (PEME) integrated high pressure hydrogen gas storage system whose capacity is 3 kg/h. For this purpose, the indicators, previously used in the literature, are taken into account and their variations are parametrically studied as a function of the PEME operating pressure and storage pressure by considering i) PEME operating temperature at 70 °C, ii) PEME operating pressures at 10, 30, 50 and 100 bar, iii) hydrogen gas flow rate at 3 kg/h and iv) storage pressure between 200 and 900 bar. Consequently, the results from the parametric investigation indicate that, with the ascent of storage pressure from 200 to 900 bar at a constant PEME operating pressure (=50 bar), exergetic efficiency changes decreasingly between 0.612 and 0.607 while exergetic sustainability between 1.575 and 1.545. However, it is estimated that waste exergy ratio changes increasingly between 0.388 and 0.393 while environmental effect factor between 0.635 and 0.647. Additionally, it is said that the higher PEME outlet pressure causes the higher exergetic sustainability index, the lower environmental effect factor, the lower waste exergy output, the higher exergetic efficiency. However, the higher storage pressure causes the lower exergetic efficiency, the higher waste exergy output, the higher environmental effect factor and the lower exergetic sustainability index. Thus, it is recommended that this type of the system should be operated at higher PEME outlet pressure, and at an optimum hydrogen storage pressure.

9-3-2 液体アンモニアとアルカリ金属水素化物を用いた化学的高圧水素製造(Session 9-3 水素製造・貯蔵・利用III)

9-3-2 液体アンモニアとアルカリ金属水素化物を用いた化学的高圧水素製造(Session 9-3 水素製造・貯蔵・利用III)

Energetic evaluation of high pressure PEM electrolyzer systems for intermediate storage of renewable energies

Three pathways for high pressure hydrogen production by means of water electrolysis are energetically compared. Besides the two classic paths, comprising either the pressurization of the product gas (path I) or the mechanical pressurization of the feed water (path II), a third path is discussed. It involves the electrochemical co-compression during the electrolysis.The energetic evaluation is based on a uniform model description of the different hydrogen production pathways. It consists of integral, steady-state balances for energy, entropy and mass as well as a modern equation of state. From this the reversible energy demand is used to identify the inherent thermodynamic drawbacks of the pathways. The additional consideration of irreversibilities allows for the determination of efficiency losses due to device specific characteristics.For hydrogen delivery pressures of up to 40bar the classical pathways are out-performed by path III. Since the hydrogen is already produced at elevated pressure this eliminates the need for an energy consuming mechanical hydrogen compression and spares the additional energy demand due to the oxygen pressurization. However, with increasing pressure differences the hydrogen back-diffusion strongly decreases the Faradaic efficiency of the asymmetric electrolyzer that has to be compensated by an additional energy supply.

Studies of Energy Efficiency and a Control of High-Pressure Hydrogen Production

We developed a high-pressure electrolyzer system (HPESes) using LabVIEW. HPESes play a very important role for hydrogen stations and independent distributed power sources, which store hydrogen gases in high-pressure cylinders or hydrogen storing alloys. The experimental results show that this system can automatically rise the pressure of hydrogen up to 0.7MPa. The energy efficiency of this system is higher than that of a typical system using a compressor.

Studies of Energy Efficiency and a Control of High-pressure Hydrogen Production

not Available.

On-Demand Hydrogen via High-Pressure Water Reforming for Military Fuel Cell Applications

Researchers have developed a high-pressure water-reforming (HPWR) process that produces high-pressure hydrogen from a jet fuel feedstock. Converting petroleum-based fuels to hydrogen for fuel cell use is a unique approach to reducing military petroleum consumption by improving petroleum utilization efficiency. HPWR is an attractive option because, unlike traditional steam methane reforming, it does not require postreformer hydrogen compression and storage. A HPWR apparatus was designed and manufactured. Several catalysts were tested for their ability to produce high-pressure hydrogen from jet fuel. S-8, which is a jet fuel derived from natural gas, was used as a model feedstock for initial experiments because the fuel is sulfur and aromatics free. After optimizing with S-8, JP-8 will be utilized for future experiments. The most promising catalyst produced a 4000psi(gauge) product gas stream that contained 54mol% hydrogen. These experimental results show that HPWR is a promising solution for high-pressure hydrogen production as a key step toward reducing military petroleum use.

Thermodynamics aspect of high pressure hydrogen production by water electrolysis

Hydrogen can be produced from water electrolysis which can operate at atmospheric pressure or high pressure. Today’s industry including vehicle one, devotes efforts to produce high pressure hydrogen by using pressurized electrolyser. The purpose of this work is to estimate the ideal electrical energy needed for high pressure hydrogen under high pressure water electrolysis conditions. Calculations are based on the estimation of the enthalpy and free Gibbs energy of water electrolysis at various pressures and temperatures, referring to both the work of LeRoy & Onda.