Journal Description
Hydrogen
Hydrogen
is an international, peer-reviewed, open access journal on all aspects of hydrogen published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within CAPlus / SciFinder, and other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 15.7 days after submission; acceptance to publication is undertaken in 3.3 days (median values for papers published in this journal in the first half of 2023).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
Latest Articles
Effect of Ti-Based Additives on the Hydrogen Storage Properties of MgH2: A Review
Hydrogen 2023, 4(3), 523-541; https://doi.org/10.3390/hydrogen4030034 - 05 Aug 2023
Abstract
For the few past decades, study of new hydrogen storage materials has been captivating scientists worldwide. Magnesium hydride, MgH2, is considered one of the most promising materials due to its low cost, high hydrogen capacity, reversibility and the abundance of Mg.
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For the few past decades, study of new hydrogen storage materials has been captivating scientists worldwide. Magnesium hydride, MgH2, is considered one of the most promising materials due to its low cost, high hydrogen capacity, reversibility and the abundance of Mg. However, it requires further research to improve its hydrogen storage performance as it has some drawbacks such as poor dehydrogenation kinetic, high operational temperature, which limit its practical application. In this study, we introduce an overview of recent progress in improving the hydrogen storage performance of MgH2 by the addition of titanium-based additives, which are one of the important groups of additives. The role of Ti-based additive hydrides, oxides, halides, carbides and carbonitrides are overviewed. In addition, the existing challenges and future perspectives of Mg-based hydrides are also discussed.
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(This article belongs to the Special Issue Feature Papers in Hydrogen (Volume 2))
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Tailoring Ceria-Based Nanocatalysts for Enhanced Performance in Steam Reforming Processes: Exploring Fundamentals and Morphological Modulations
by
, , , , and
Hydrogen 2023, 4(3), 493-522; https://doi.org/10.3390/hydrogen4030033 - 31 Jul 2023
Abstract
Ceria-based nanostructures, employed as catalytic supports for noble and non-noble metals, are well-known for their remarkable activity in steam-reforming reactions, exceptional resistance to degradation, and thermal stability. However, the catalytic activity and selectivity of such systems are strongly dependent on the size and
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Ceria-based nanostructures, employed as catalytic supports for noble and non-noble metals, are well-known for their remarkable activity in steam-reforming reactions, exceptional resistance to degradation, and thermal stability. However, the catalytic activity and selectivity of such systems are strongly dependent on the size and shape of ceria, making it possible to tune the oxide properties, affecting catalyst design and performance. The rational manipulation of ceria nanostructures offers various features that directly impact steam-reforming transformations, including the possibility of tuning oxygen vacancies, redox properties, and oxygen storage capacity. Thus, the importance of shape control in ceria nanomaterials is highlighted herein, emphasizing how the surface atomic configurations (exposure of different facets) significantly impact their efficiency. Although the main focus of this review is to discuss how the catalyst design may affect the performance of hydrogen production, some other elemental studies are shown, when necessary, to exemplify the level of deepness (or not) that literature has reached. Thus, an overview of ceria properties and how the physicochemical control of nanostructures contributes to their tuning will be presented, as well as a discussion regarding elemental materials design and the most prominent synthetic procedures; then, we select some metals (Ni, Co, and Pt) to discuss the understanding of such aspects for the field. Finally, challenges and perspectives for nanoengineering catalysts based on shape-controlled ceria nanostructures will be described to possibly improve the performance of designed catalysts for steam-reforming reactions. Although there are other literature reviews on ceria-based catalysts for these reactions, they do not specifically focus on the influence of the size and shape of the oxide.
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(This article belongs to the Special Issue Feature Papers in Hydrogen (Volume 2))
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Material and Performance Optimisation for Syngas Preparation Using Artificial Intelligence (AI)-Based Machine Learning (ML)
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Hydrogen 2023, 4(3), 474-492; https://doi.org/10.3390/hydrogen4030032 - 25 Jul 2023
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Working towards a more sustainable future with zero emissions, the International Future Laboratory for Hydrogen Economy at the Technical University of Munich (TUM) exhibits concerted efforts across various hydrogen technologies. The current research focuses on pre-reforming processes for high-quality reversible solid oxide cell
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Working towards a more sustainable future with zero emissions, the International Future Laboratory for Hydrogen Economy at the Technical University of Munich (TUM) exhibits concerted efforts across various hydrogen technologies. The current research focuses on pre-reforming processes for high-quality reversible solid oxide cell feedstock preparation. An AI-based machine learning model has been developed, trained, and deployed to predict and optimise the controlled utilisation of methane gas. Using a blend of design of experiments and a validated 3D computational fluid dynamics model, pre-reforming process data have been generated for various syngas mixtures. The results of this study indicate that it is possible to achieve a targeted methane utilisation rate of 20% while decreasing the amount of catalyst material by 11%. Furthermore, it was found that precise process parameters could be determined efficiently and with minimal resource consumption in order to achieve higher methane fuel utilisation rates of 25% and 30%. The machine learning model has been effectively employed to analyse and optimise the fuel outlet conditions of the pre-reforming process, contributing to a better understanding of high-quality syngas preparation and furthering sustainable research efforts for a safe reversible solid oxide cell (r-SOC) process.
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Hydrogen-Nano-Bubble-Rich Water in Bucket/Bathtub Improves Intractable Skin Roughness
Hydrogen 2023, 4(3), 456-473; https://doi.org/10.3390/hydrogen4030031 - 19 Jul 2023
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Determining how to apply hydrogen as a therapeutic/preventive antioxidant for oxidative-stress-related diseases practically in daily life has not been studied. The effects of bathtubs and buckets filled with hydrogen water (41 °C, >10 min bathing) were investigated on six subjects, without a medical
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Determining how to apply hydrogen as a therapeutic/preventive antioxidant for oxidative-stress-related diseases practically in daily life has not been studied. The effects of bathtubs and buckets filled with hydrogen water (41 °C, >10 min bathing) were investigated on six subjects, without a medical prescription, suffering from skin roughness on the foot, hand, finger, or elbow. They were also treated with an electrolyzer composed of a lattice-shaped, microscopically flat, platinum-plated three-layer electrode, except for one subject who was treated with a micro-porous emittance terminal hydrogen-jetting apparatus, resulting in improvements in both cases. For another subject with similar skin roughness on both hands, immersing the right hand in an electrolytically generated hydrogen water bucket showed more marked improvement than immersing the left hand in a bucket with normal water. The nano-bubbles (average, mode, and median sizes of 157 nm, 136 nm, and 94 nm, respectively) increased 3.79 fold to 2.20 × 108/mL after 30 min electrolysis with 2 L of tap water and were boiling (98 °C, 2 min)-resistant, with heat stability in nano-bubbles as small as 69–101 nm, as evaluated by laser-beam-based Brownian movement trailing Nano-Sight analysis. The marked increase in nano-bubbles caused by electrolysis correlated with an increase in dissolved hydrogen (<15 μg/L to 527 μg/L) but not a decrease in dissolved oxygen (9.45 mg/L to 6.94 mg/L). Thus, the present study proposed the novelty of hydrogen regarding its contribution to health from the perspective that hydrogen-nano-bubble-rich water in a foot bucket, which was additively used together with a conventional bathtub and can be frequently used in daily life, improved diverse types of skin roughness.
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The Effect of Liquid Hydrogen Tank Size on Self-Pressurization and Constant-Pressure Venting
Hydrogen 2023, 4(3), 444-455; https://doi.org/10.3390/hydrogen4030030 - 19 Jul 2023
Abstract
Hydrogen represents a promising renewable fuel, and its broad application can lead to drastic reductions in greenhouse gas emissions. Keeping hydrogen in liquid form helps achieve high energy density, but also requires cryogenic conditions for storage as hydrogen evaporates at temperatures of about
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Hydrogen represents a promising renewable fuel, and its broad application can lead to drastic reductions in greenhouse gas emissions. Keeping hydrogen in liquid form helps achieve high energy density, but also requires cryogenic conditions for storage as hydrogen evaporates at temperatures of about 20 K, which can lead to a large pressure build-up in the tank. This paper addresses the unsteady thermal modeling of cryogenic tanks with liquid hydrogen. Considering the liquid and vapor phases in the tank as two nodes with averaged properties, a lumped-element method of low computational cost is developed and used for simulating two regimes: self-pressurization (also known as autogenous pressurization, or pressure build-up in the closed tank due to external heat leaks) and constant-pressure venting (when some hydrogen is let out of the tank to maintain pressure at a fixed level). The model compares favorably (within several percent for pressure) to experimental observations for autogenous pressurization in a NASA liquid hydrogen tank. The two processes of interest in this study are numerically investigated in tanks of similar shapes but different sizes ranging from about 2 to 1200 m3. Pressure and temperature growth rates are characterized in closed tanks, where the interfacial mass transfer manifests initial condensation followed by more pronounced evaporation. In tanks where pressure is kept fixed by venting some hydrogen from the vapor domain of the tank, the initial venting rate significantly exceeds evaporation rate, but after a settling period, magnitudes of both rates approach each other and continue evolving at a slower pace. The largest tank demonstrates a six-times-lower pressure rise than the smallest tank over a 100 h period. The relative boil-off losses in continuously vented tanks are found to be approximately proportional to the inverse of the tank diameter, thus generally following simple Galilean scaling with a few percent deviation due to scale effects. The model developed in this work is flexible for analyzing a variety of processes in liquid hydrogen storage systems, raising efficiencies, which is critically important for a future economy based on renewable energy.
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(This article belongs to the Special Issue Feature Papers in Hydrogen (Volume 2))
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Device for Controlled Production of Hydrogen
Hydrogen 2023, 4(3), 434-443; https://doi.org/10.3390/hydrogen4030029 - 15 Jul 2023
Abstract
In this work, the production of hydrogen from the sodium borohydride (NaBH4) reaction was studied using an experimental bench test in a passive device operating with or without minimal external energy input. The system consists of a reactor in which a
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In this work, the production of hydrogen from the sodium borohydride (NaBH4) reaction was studied using an experimental bench test in a passive device operating with or without minimal external energy input. The system consists of a reactor in which a mixture based on sodium borohydride powders and an organic acid is confined. A flow of water feeds the area in which the solid mixture is confined, which undergoes a hydrolysis reaction and this generates gaseous hydrogen. The hydrogen thus produced, already saturated with water vapor, is particularly suitable for feeding polymer electrolyte fuel cells for the production of electricity because it does not require further humidification. The borohydride–organic acid coupling studied for this device, and its chemical process, provides high reaction and conversion kinetics, presenting remarkable chemical stability over time.
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(This article belongs to the Topic Hydrogen Generation, Storage, and Utilization)
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Investigation of Different Load Characteristics, Component Dimensioning, and System Scaling for the Optimized Design of a Hybrid Hydrogen-Based PV Energy System
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and
Hydrogen 2023, 4(3), 408-433; https://doi.org/10.3390/hydrogen4030028 - 13 Jul 2023
Abstract
The realization of a carbon-neutral civilization, which has been set as a goal for the coming decades, goes directly hand-in-hand with the need for an energy system based on renewable energies (REs). Due to the strong weather-related, daily, and seasonal fluctuations in supply
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The realization of a carbon-neutral civilization, which has been set as a goal for the coming decades, goes directly hand-in-hand with the need for an energy system based on renewable energies (REs). Due to the strong weather-related, daily, and seasonal fluctuations in supply of REs, suitable energy storage devices must be included for such energy systems. For this purpose, an energy system model featuring hybrid energy storage consisting of a hydrogen unit (for long-term storage) and a lithium-ion storage device (for short-term storage) was developed. With a proper design, such a system can ensure a year-round energy supply by using electricity generated by photovoltaics (PVs). In the energy system that was investigated, hydrogen ( ) was produced by using an electrolyser (ELY) with a PV surplus during the summer months and then stored in an tank. During the winter, due to the lack of PV power, the is converted back into electricity and heat by a fuel cell (FC). While the components of such a system are expensive, a resource- and cost-efficient layout is important. For this purpose, a Matlab/Simulink model that enabled an energy balance analysis and a component lifetime forecast was developed. With this model, the results of extensive parameter studies allowed an optimized system layout to be created for specific applications. The parameter studies covered different focal points. Several ELY and FC layouts, different load characteristics, different system scales, different weather conditions, and different load levels—especially in winter with variations in heating demand—were investigated.
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CO Removal from Hydrogen Stream through Methanation on Ru/C Catalysts Doped with Lanthanum and Barium
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, , , and
Hydrogen 2023, 4(2), 389-407; https://doi.org/10.3390/hydrogen4020027 - 20 Jun 2023
Abstract
The influence of the lanthanum and barium addition on the physicochemical properties and catalytic behavior of the Ru/C catalyst for CO methanation was investigated. The catalyst was doped with La or with La plus Ba. It was found out that there are various
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The influence of the lanthanum and barium addition on the physicochemical properties and catalytic behavior of the Ru/C catalyst for CO methanation was investigated. The catalyst was doped with La or with La plus Ba. It was found out that there are various ways the additives were applied in the study, thus changing the catalytic performance of the basic material and influencing the susceptibility of the carbon support in relation to undesired methanation. The highest catalytic activity, 23.46 (mmol CO/gC+Ru × h), was achieved for the LaRu/C system, with methane selectivity exceeding 80% over the whole temperature range. Ba addition caused a significant decrease in activity. TG-MS studies revealed that both La and Ba improved the resistance of the carbon support to undesired methanation. Detailed characterization methods, employing XRPD, Raman spectroscopy, CO chemisorption, and SEM-EDX, showed that the catalytic behavior of the studied catalysts was attributed to lanthanum distribution over the Ru/C materials surface and structural changes in the carbon support affecting electron supply to the metallic active phase.
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(This article belongs to the Topic Hydrogen Production Processes)
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Gasification of Lower Monohydric Alcohols by Solution Plasma Treatment and Its Reaction Mechanism
Hydrogen 2023, 4(2), 373-388; https://doi.org/10.3390/hydrogen4020026 - 16 Jun 2023
Abstract
Solution plasma is a gas-phase discharge in the vapor bubbles in a solution and has the potential to efficiently produce H2 by decomposing aqueous alcohols. However, the mechanism of alcohol decomposition in solution plasma remains unclear. In this study, lower monohydric alcohols
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Solution plasma is a gas-phase discharge in the vapor bubbles in a solution and has the potential to efficiently produce H2 by decomposing aqueous alcohols. However, the mechanism of alcohol decomposition in solution plasma remains unclear. In this study, lower monohydric alcohols (methanol and ethanol, as well as 1- and 2-propanol) were treated in solution plasma, and in this paper, the gasification mechanism is discussed. The gases produced from these alcohols were mainly H2 and CO, with small ratios of C1–C3 hydrocarbons. Thus, the O/C ratio in the product gas was close to 1 for all alcohols, and most of the C atoms in the alcohols were bonded to O atoms. This excess of O atoms could have only come from water, suggesting a strong contribution of OH radicals from water for gasification. However, the C1–C3 hydrocarbons were produced solely by the decomposition of the alcohol. For both decomposition routes, possible reaction pathways are proposed that are consistent with the experimental facts such as the composition of the product gas and the intermediates detected.
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Natural Gas Pyrolysis in a Liquid Metal Bubble Column Reaction System—Part II: Pyrolysis Experiments and Discussion
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, , , , , and
Hydrogen 2023, 4(2), 357-372; https://doi.org/10.3390/hydrogen4020025 - 09 Jun 2023
Abstract
This contribution presents the results of continued investigations on the production of hydrogen by means of pyrolysis in a liquid metal bubble column reactor, as developed at the Karlsruhe Institute of Technology in recent years. Part I of this contribution described the motivation
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This contribution presents the results of continued investigations on the production of hydrogen by means of pyrolysis in a liquid metal bubble column reactor, as developed at the Karlsruhe Institute of Technology in recent years. Part I of this contribution described the motivation and the methodology of this study, as well as a significant scale-up, and discussed its results for pure methane pyrolysis. Here in part II, two additional experimental campaigns with methane–ethane mixtures (MEMs) and high-calorific natural gas (nGH) will be presented and discussed for the first time, using the up-scaled liquid metal bubble column reactor. It could be proven that an MEM as the feed gas led to an increase in methane conversion at low temperatures, which is consistent with the literature data. The nGH pyrolysis confirms this trend and also results in a significant rise in methane conversion compared to pure methane pyrolysis. Furthermore, the nGH pyrolysis leads to an increased methane conversion even at higher temperatures compared to MEM pyrolysis. Additionally, both MEM and nGH pyrolysis also showed a shift in the formation of by-products toward lower temperatures.
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LCA Analysis Decarbonisation Potential of Aluminium Primary Production by Applying Hydrogen and CCUS Technologies
Hydrogen 2023, 4(2), 338-356; https://doi.org/10.3390/hydrogen4020024 - 20 May 2023
Cited by 1
Abstract
The energy intensity and high emissions of extractive industries bring a major need for decarbonisation actions. In 2021, extraction and primary processing of metals and minerals were responsible for 4.5 Gt of equivalent CO2. The aluminium industry specifically accounted for total
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The energy intensity and high emissions of extractive industries bring a major need for decarbonisation actions. In 2021, extraction and primary processing of metals and minerals were responsible for 4.5 Gt of equivalent CO2. The aluminium industry specifically accounted for total emissions of 1.1 Gt CO2 eq. per year. Reaching the European milestone of zero emissions by 2050, requires a 3% annual reduction. To achieve this, the industry has searched for innovative solutions, considering the treatment of emitted CO2 with techniques such as Carbon Capture Utilisation and Storage (CCUS), or the prevention of CO2 formation on the first place by utilising alternative fuels such as hydrogen (H2). This study aims to comprehensively compare the overall environmental performance of different strategies for addressing not only greenhouse gas (GHG) emission reduction potential, but also emissions to air in general, as well as freshwater and terrestrial ecotoxicity, which are commonly overlooked. Specifically, a Life Cycle Assessment (LCA) is conducted, analysing four scenarios for primary Al production, utilising (1) a combination of fossil fuels, specifically Natural Gas (NG), Light Fuel Oil (LFO) and Heavy Fuel Oil (HFO) (conventional approach); (2) carbon capture and geological storage; (3) Carbon Capture and Utilisation (CCU) for methanol (MeOH) production and (4) green H2, replacing NG. The results show that green H2 replacing NG is the most environmentally beneficial option, accounting for a 10.76% reduction in Global Warming Potential (GWP) and 1.26% in Photochemical Ozone Formation (POF), while all other impact categories were lower compared to CCUS. The results offer a comprehensive overview to support decision-makers in comparing the overall environmental impact and the emission reduction potential of the different solutions.
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(This article belongs to the Special Issue Feature Papers in Hydrogen (Volume 2))
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Geochemical Effects on Storage Gases and Reservoir Rock during Underground Hydrogen Storage: A Depleted North Sea Oil Reservoir Case Study
Hydrogen 2023, 4(2), 323-337; https://doi.org/10.3390/hydrogen4020023 - 18 May 2023
Cited by 2
Abstract
In this work, geochemical modelling using PhreeqC was carried out to evaluate the effects of geochemical reactions on the performance of underground hydrogen storage (UHS). Equilibrium, exchange, and mineral reactions were considered in the model. Moreover, reaction kinetics were considered to evaluate the
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In this work, geochemical modelling using PhreeqC was carried out to evaluate the effects of geochemical reactions on the performance of underground hydrogen storage (UHS). Equilibrium, exchange, and mineral reactions were considered in the model. Moreover, reaction kinetics were considered to evaluate the geochemical effect on underground hydrogen storage over an extended period of 30 years. The developed model was first validated against experimental data adopted from the published literature by comparing the modelling and literature values of H2 and CO2 solubility in water at varying conditions. Furthermore, the effects of pressure, temperature, salinity, and CO2% on the H2 and CO2 inventory and rock properties in a typical sandstone reservoir were evaluated over 30 years. Results show that H2 loss over 30 years is negligible (maximum 2%) through the studied range of conditions. The relative loss of CO2 is much more pronounced compared to H2 gas, with losses of up to 72%. Therefore, the role of CO2 as a cushion gas will be affected by the CO2 gas losses as time passes. Hence, remedial CO2 gas injections should be considered to maintain the reservoir pressure throughout the injection and withdrawal processes. Moreover, the relative volume of CO2 increases with the increase in temperature and decrease in pressure. Furthermore, the reservoir rock properties, porosity, and permeability, are affected by the underground hydrogen storage process and, more specifically, by the presence of CO2 gas. CO2 dissolves carbonate minerals inside the reservoir rock, causing an increase in the rock’s porosity and permeability. Consequently, the rock’s gas storage capacity and flow properties are enhanced.
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Preventing Hydrogen Embrittlement: The Role of Barrier Coatings for the Hydrogen Economy
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, , , , , , and
Hydrogen 2023, 4(2), 307-322; https://doi.org/10.3390/hydrogen4020022 - 17 May 2023
Abstract
Hydrogen barrier coatings are protective layers consisting of materials with a low intrinsic hydrogen diffusivity and solubility, showing the potential to delay, reduce or hinder hydrogen permeation. Hydrogen barrier coatings are expected to enable steels, which are susceptible to hydrogen embrittlement, specifically cost-effective
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Hydrogen barrier coatings are protective layers consisting of materials with a low intrinsic hydrogen diffusivity and solubility, showing the potential to delay, reduce or hinder hydrogen permeation. Hydrogen barrier coatings are expected to enable steels, which are susceptible to hydrogen embrittlement, specifically cost-effective low alloy-steels or light-weight high-strength steels, for applications in a hydrogen economy. Predominantly, ceramic coating materials have been investigated for this purpose, including oxides, nitrides and carbides. In this review, the state of the art with respect to hydrogen permeation is discussed for a variety of coatings. Al2O3, TiAlN and TiC appear to be the most promising candidates from a large pool of ceramic materials. Coating methods are compared with respect to their ability to produce layers with suitable quality and their potential for scaling up for industrial use. Different setups for the characterisation of hydrogen permeability are discussed, using both gaseous hydrogen and hydrogen originating from an electrochemical reaction. Finally, possible pathways for improvement and optimisation of hydrogen barrier coatings are outlined.
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Natural Gas Pyrolysis in a Liquid Metal Bubble Column Reaction System—Part I: Experimental Setup and Methods
by
, , , , , and
Hydrogen 2023, 4(2), 295-306; https://doi.org/10.3390/hydrogen4020021 - 17 May 2023
Abstract
Hydrogen is not only an important industrial chemical but also an energy carrier with increasing demand. However, the current production techniques are based on technologies that result in massive CO2 emissions. In contrast, the pyrolysis of alkanes in a liquid metal bubble
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Hydrogen is not only an important industrial chemical but also an energy carrier with increasing demand. However, the current production techniques are based on technologies that result in massive CO2 emissions. In contrast, the pyrolysis of alkanes in a liquid metal bubble column reactor does not lead to direct CO2 emissions. In order to transfer this technology from lab-scale to industrial applications, it has to be scaled up and the influences of the most common constituent of natural gas on the pyrolysis process have to be determined. For this study, the liquid metal bubble column technology developed at the KIT was scaled up by a factor of 3.75, referred to as the reactor volume. In this article, the experimental setup containing the reactor is described in detail. In addition, new methods for the evaluation of experimental data will be presented. The reactor, as well as the experimental results from pure methane pyrolysis (PM), will be compared to the previous generation of reactors in terms of methane conversion. It could be proven that scaling up the reactor volume did not result in a decrease in methane conversion. For part II of this publication, methane-ethane (MEM) gas mixtures and high calorific natural gas (nGH) were pyrolyzed, and the results were discussed on the basis of the present part I.
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Nuclear Motion Is Classical: Spectra of Hydrogen Chloride and Ammonia
Hydrogen 2023, 4(2), 287-294; https://doi.org/10.3390/hydrogen4020020 - 15 May 2023
Abstract
The concept of classical nuclear motion is extremely successful in describing motion at the atomic scale. In describing chemical reactions, it is even far more convincing than the picture obtained by using the Schrödinger equation for time development. However, this theory must be
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The concept of classical nuclear motion is extremely successful in describing motion at the atomic scale. In describing chemical reactions, it is even far more convincing than the picture obtained by using the Schrödinger equation for time development. However, this theory must be subject to critical tests. In particular, it must be checked if vibrational and rotational spectra are obtained correctly. Particularly critical are the spectra of small molecules containing the light hydrogen atom, since they have a distinctive rotational structure. The present study presents computations of the spectra of ammonia and hydrogen chloride using ab initio molecular dynamics, that is, by describing nuclear motion classically.
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Process Assessment of Integrated Hydrogen Production from By-Products of Cottonseed Oil-Based Biodiesel as a Circular Economy Approach
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, , , , and
Hydrogen 2023, 4(2), 272-286; https://doi.org/10.3390/hydrogen4020019 - 08 May 2023
Abstract
Cottonseed oil (CSO) is well known as one of the commercial cooking oils. However, CSO still needs to compete with other edible oils available in the market due to its small production scale and high processing cost, which makes it a potential candidate
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Cottonseed oil (CSO) is well known as one of the commercial cooking oils. However, CSO still needs to compete with other edible oils available in the market due to its small production scale and high processing cost, which makes it a potential candidate as a feedstock for biodiesel production. To date, transesterification is the most widely applied technique in the conversion of vegetable oil to biodiesel, with glycerol produced as a by-product. Large-scale biodiesel production also implies that more glycerol will be produced, which can be further utilized to synthesize hydrogen via the steam reforming route. Therefore here, an integrated biodiesel and hydrogen production from CSO was simulated using Aspen Hysys v11. Simulation results showed that the produced biodiesel has good characteristics compared to standard biodiesel. An optimum steam-to-glycerol ratio for hydrogen production was found to be 4.5, with higher reaction temperatures up to 750 °C resulting in higher hydrogen yield and selectivity. In addition, a simple economic analysis of this study showed that the integrated process is economically viable.
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Design and Scale-Up of Zero-Gap AEM Water Electrolysers for Hydrogen Production
Hydrogen 2023, 4(2), 257-271; https://doi.org/10.3390/hydrogen4020018 - 04 May 2023
Cited by 1
Abstract
The design of a 10 cm2 (3.4 cm by 3.4 cm) and a 100 cm2 (10 cm by 10 cm) anion exchange membrane (AEM) water electrolyser cell for hydrogen production are described. The AEM cells are based on a zero-gap configuration
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The design of a 10 cm2 (3.4 cm by 3.4 cm) and a 100 cm2 (10 cm by 10 cm) anion exchange membrane (AEM) water electrolyser cell for hydrogen production are described. The AEM cells are based on a zero-gap configuration where the AEM is sandwiched between the anode and cathode so as to minimise voltage drop between the electrodes. Nonprecious nickel-based metal alloy and metal oxide catalysts were employed. Various experiments were carried out to understand the effects of operating parameters such as current densities, electrolyte concentrations, and testing regimes on the performance of both 10 cm2 and 100 cm2 AEM electrolyser cells. Increasing electrolyte concentration was seen to result in reductions in overpotentials which were proportional to current applied, whilst the use of catalysts improved performance consistently over the range of current densities tested. Extended galvanostatic and intermittent tests were demonstrated on both 10 cm2 and 100 cm2 cells, with higher voltage efficiencies achieved with the use of electrocatalysts. Stability tests in the 100 cm2 AEM electrolyser cell assembled with catalyst-coated electrodes demonstrated that the cell voltages remained stable at 2.03 V and 2.17 V during 72 h operation in 4 M KOH and 1 M KOH electrolyte, respectively, at a current density of 0.3 A cm−2 at 323 K. The inclusion of cycling load tests in testing protocols is emphasized for rational evaluation of cell performance as this was observed to speed up the rate of degradation mechanisms such as membrane degradation.
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A Case Study Approach: Summary of Some Results on the Effects of Hydrogen Exposure on the Mechanical Properties of Palladium and the Alloy Systems Pd1−xMx, M = Ag, Cu, Mn; x = 5 − 0.25
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Hydrogen 2023, 4(2), 237-256; https://doi.org/10.3390/hydrogen4020017 - 27 Apr 2023
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Selected results of investigations focused on the changes to some mechanical properties of palladium and several palladium-based alloys caused by exposure to hydrogen have been collected and presented. The findings indicate that the mechanical properties of pure palladium are highly susceptible to alteration
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Selected results of investigations focused on the changes to some mechanical properties of palladium and several palladium-based alloys caused by exposure to hydrogen have been collected and presented. The findings indicate that the mechanical properties of pure palladium are highly susceptible to alteration upon exposure to hydrogen. In the cases of alloying palladium with silver and copper, the alloys, as compared to palladium, appear to resist changes to mechanical properties. In the case of alloying palladium with manganese, the interesting order–disorder phenomenon plays an important role on the effects of hydrogen exposure on their mechanical properties.
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Investigation of Microscale Periodic Ni-Mg-Ni-Mg Film Structures as Metal-Hydride Hydrogen Accumulators
Hydrogen 2023, 4(2), 226-236; https://doi.org/10.3390/hydrogen4020016 - 24 Apr 2023
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Here, the authors report the results of their study on the key characteristics of microscale periodic Ni-Mg-Ni-Mg film structures as metal-hydride hydrogen accumulators, namely, the microstructure, phase state, operation temperatures and rate of the sorption/desorption processes, complete and reversible mass content of hydrogen,
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Here, the authors report the results of their study on the key characteristics of microscale periodic Ni-Mg-Ni-Mg film structures as metal-hydride hydrogen accumulators, namely, the microstructure, phase state, operation temperatures and rate of the sorption/desorption processes, complete and reversible mass content of hydrogen, and enthalpy of metal hydrides’ phase-formation. The study has shown that hydride-formation films can be saturated with up to 7.0–7.5 wt.% of hydrogen at pressures up to 30 atm and temperatures of 200–250 °C, with a reversible amount of stored hydrogen up to 3.4 wt.% during its desorption at a pressure of 1 atm and temperatures of 250–300 °C with the phase-formation enthalpy in the range of 19.8–46.7 kJ/mol H2 depending on the nickel content (the thickness of the nickel layer). Structural and constructive schemes are proposed for film metal-hydride hydrogen accumulators for various applications of the hydrogen power industry.
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Open AccessArticle
Evaluation of Hydrogen Blend Stability in Low-Pressure Gas Distribution
Hydrogen 2023, 4(2), 210-225; https://doi.org/10.3390/hydrogen4020015 - 14 Apr 2023
Abstract
Natural gas distribution companies are developing ambitious plans to decarbonize the services that they provide in an affordable manner and are accelerating plans for the strategic integration of renewable natural gas and the blending of green hydrogen produced by electrolysis, powered with renewable
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Natural gas distribution companies are developing ambitious plans to decarbonize the services that they provide in an affordable manner and are accelerating plans for the strategic integration of renewable natural gas and the blending of green hydrogen produced by electrolysis, powered with renewable electricity being developed from large new commitments by states such as New York and Massachusetts. The demonstration and deployment of hydrogen blending have been proposed broadly at 20% of hydrogen by volume. The safe distribution of hydrogen blends in existing networks requires hydrogen blends to exhibit similar behavior as current supplies, which are also mixtures of several hydrocarbons and inert gases. There has been limited research on the properties of blended hydrogen in low-pressure natural gas distribution systems. Current natural gas mixtures are known to be sufficiently stable in terms of a lack of chemical reaction between constituents and to remain homogeneous through compression and distribution. Homogeneous mixtures are required, both to ensure safe operation of customer-owned equipment and for safety operations, such as leak detection. To evaluate the stability of mixtures of hydrogen and natural gas, National Grid experimentally tested a simulated distribution natural gas pipeline with blends containing hydrogen at up to 50% by volume. The pipeline was outfitted with ports to extract samples from the top and bottom of the pipe at intervals of 20 feet. Samples were analyzed for composition, and the effectiveness of odorant was also evaluated. The new results conclusively demonstrate that hydrogen gas mixtures do not significantly separate or react under typical distribution pipeline conditions and gas velocity profiles. In addition, the odorant retained its integrity in the blended gas during the experiments and demonstrated that it remains an effective method of leak detection.
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(This article belongs to the Special Issue Feature Papers in Hydrogen (Volume 2))
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