Hydrogen Energy Technologies, 2nd Edition

Topic Information

Dear Colleagues,

Hydrogen is becoming a major contributor to decarbonising modern economies across the globe. This Topic is a continuation of the previous successful Topic “Hydrogen Energy Technologies”.

The scene is being set for hydrogen to be a major player in decarbonising our modern economy. This is happening at the same time as, with the increasing level of investment driven by the demand side, the hydrogen industry is positioning itself towards mass production in the coming years that would significantly drive down costs even faster than what we have witnessed in the past couple of decades. In line with all these developments, research and innovation in this field are expanding at a rapid rate, and we in the Energies journal are committed to facilitating the communication of high-quality studies in this field. This Topic focuses on the latest fundamentals and applied innovations in the field of hydrogen energy covering the production, storage, distribution, and utilisation of hydrogen energy in various stationary and mobile applications. The Topic includes but is not limited to:

• Hydrogen production methods;
• Hydrogen distribution;
• Novel hydrogen storage solutions;
• Large-scale hydrogen-based energy storage;
• Integrated renewable hydrogen systems;
• Fuel cells and electrolysers;
• Hydrogen systems modelling and optimisation (including numerical and analytical modelling, computational chemistry, etc.);
• Hydrogen system components and design (including MEA, catalyst layer, electrodes, GDL, membrane, bipolar plates, flow field, etc.);
• Hydrogen system operation and optimisation;
• Hydrogen for stationary and mobile applications;
• Control solutions for hydrogen systems;
• Hydrogen system/component manufacturing;
• Advanced hydrogen materials;
• Thermofluid modelling of hydrogen systems;
• Hydrogen economy;
• Hydrogen safety.

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Energies energies	3.0	6.2	2008	16.8 Days	CHF 2600
Catalysts catalysts	3.8	6.8	2011	13.9 Days	CHF 2200
Hydrogen hydrogen	-	3.6	2020	14.8 Days	CHF 1000
Nanoenergy Advances nanoenergyadv	-	-	2021	33.8 Days	CHF 1000

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Published Papers (10 papers)

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All Energies Catalysts Hydrogen Nanoenergy Advances

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Supplementary material:
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20 pages, 10101 KiB  

Open AccessArticle

Enhanced Room-Temperature Hydrogen Physisorption in Zeolitic Imidazolate Frameworks and Carbon Nanotube Hybrids

by Syedvali Pinjari, Tapan Bera and Erik Kjeang

Nanoenergy Adv. 2025, 5(2), 5; https://doi.org/10.3390/nanoenergyadv5020005 - 3 Apr 2025

Viewed by 207

Abstract

In this work, zeolitic imidazolate frameworks (ZIF-8, ZIF-67, and ZC-ZIF) and their hybrid composites with carboxylate-functionalized carbon nanotubes (fCNTs) are synthesized through low-cost synthesis methods for enhanced physisorption-based hydrogen storage at room temperature. While both base and hybrid structures are designed to improve [...] Read more.

In this work, zeolitic imidazolate frameworks (ZIF-8, ZIF-67, and ZC-ZIF) and their hybrid composites with carboxylate-functionalized carbon nanotubes (fCNTs) are synthesized through low-cost synthesis methods for enhanced physisorption-based hydrogen storage at room temperature. While both base and hybrid structures are designed to improve hydrogen uptake, the base materials exhibit the most notable performance compared to their carbon hybrid counterparts. The structural analysis confirms that all samples maintain high crystallinity and exhibit well-defined rhombic dodecahedral morphologies. The hybrid composites, due to the intercalation of fCNTs, show slightly larger particle sizes than their base materials. X-ray photoelectron spectroscopy reveals strong nitrogen–metal coordination in the ZIF structures, contributing to a larger specific surface area (SSA) and optimal microporous properties. A linear fit of SSA and hydrogen uptake indicates improved hydrogen transport at low pressures due to fCNT addition. ZIF-8 achieves the highest SSA of 2023.6 m²/g and hydrogen uptake of 1.01 wt. % at 298 K and 100 bar, with 100% reversible adsorption. Additionally, ZIF-8 exhibits excellent cyclic repeatability, with only 10% capacity reduction after five adsorption/desorption cycles. Kinetic analysis reveals that hydrogen adsorption in the ZIF materials is governed by a combination of surface adsorption, intraparticle diffusion, and complex pore filling. These findings underscore the potential of ZIFs as superior materials for room-temperature hydrogen storage. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Edition)

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20 pages, 5442 KiB  

Open AccessArticle

Analytical Modeling of Filling Times for Metal Hydride–Hydrogen Storage Tanks With and Without Heat Reaction Recovery

by Fatma Bouzgarrou, Sofiene Mellouli and Abdullah A. Faqihi

Energies 2025, 18(1), 54; https://doi.org/10.3390/en18010054 - 27 Dec 2024

Viewed by 711

Abstract

The analysis of metal hydride (MH) tanks requires numerical modeling, which can be complemented by analytical studies. These analytical studies are valuable for swiftly sizing efficient reservoirs intended for hydrogen or thermal energy storage systems. This study aims to develop an analytical model [...] Read more.

The analysis of metal hydride (MH) tanks requires numerical modeling, which can be complemented by analytical studies. These analytical studies are valuable for swiftly sizing efficient reservoirs intended for hydrogen or thermal energy storage systems. This study aims to develop an analytical model for estimating the filling time of various metal hydride–hydrogen storage tanks under two conditions, with and without heat reaction recovery, utilizing phase change material (PCM). Four scenarios of the metal hydride tank are considered: (i) one with an external electrical drum heater, (ii) one with an external heat transfer fluid, (iii) one with a PCM jacket, and (iv) one with a sandwiched MH-PCM configuration. Furthermore, this study investigates the influence of the MH tank design, geometric parameters (dimensions, geometry), and operational conditions (pressure and temperature) on the filling time. Overall, this investigation offers a basis for calculating the filling times of various metal hydride–hydrogen storage tank types, enabling well-informed design and system optimization decisions. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Edition)

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18 pages, 4659 KiB  

Open AccessArticle

Numerical Analysis of Flow in U-Type Solid Oxide Fuel Cell Stacks

by Hao Yuan Yin, Kun Woo Yi, Young Jin Kim, Hyeon Jin Kim, Kyong Sik Yun and Ji Haeng Yu

Energies 2024, 17(22), 5764; https://doi.org/10.3390/en17225764 - 18 Nov 2024

Cited by 1 | Viewed by 929

Abstract

Numerical analysis of a U-type solid oxide fuel cell stack was performed using computational fluid dynamics to investigate the effects of stack capacities and fuel/air utilization rates on the internal flow uniformity. The results indicated that increasing the fuel/air utilization rate improved the [...] Read more.

Numerical analysis of a U-type solid oxide fuel cell stack was performed using computational fluid dynamics to investigate the effects of stack capacities and fuel/air utilization rates on the internal flow uniformity. The results indicated that increasing the fuel/air utilization rate improved the gas flow uniformity within the stack for the same stack capacity. The uniformity in the anode fluid domain was better than that in the cathode fluid domain. Furthermore, the flow uniformity within the stack was associated with the percentage of pressure drop in the core region of the stack. The larger the percentage of pressure drop in the core region, the more uniform the flow inside the stack. Additionally, under a fuel utilization rate of 75%, the computational results exhibited excessively high fuel utilization rates in the top cell of a 3 kWe stack, indicating a potential risk of fuel depletion during actual stack operation. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Edition)

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15 pages, 4465 KiB  

Open AccessArticle

Comparison of the Temperature, Radiation, and Heat Flux Distribution of a Hydrogen and a Methane Flame in a Crucible Furnace Using Numerical Simulation

by Alexander Mages and Alexander Sauer

Hydrogen 2024, 5(3), 459-473; https://doi.org/10.3390/hydrogen5030026 - 21 Jul 2024

Cited by 2 | Viewed by 1520

Abstract

Sustainable technologies to replace current fossil solutions are essential to meet future CO₂ emission reduction targets. Therefore, this paper compares key performance indicators of a hydrogen- and a methane-flame-fired crucible furnace with computational fluid dynamics simulations at identical firing powers, aiming to [...] Read more.

Sustainable technologies to replace current fossil solutions are essential to meet future CO₂ emission reduction targets. Therefore, this paper compares key performance indicators of a hydrogen- and a methane-flame-fired crucible furnace with computational fluid dynamics simulations at identical firing powers, aiming to fully decarbonize the process. Validated numerical models from the literature were used to compare temperatures, radiation fields, radiation parameters and heat transfer characteristics. As a result, we observed higher combustion temperatures and a 19.0% higher fuel utilization rate in the hydrogen case, indicating more efficient operating modes, which could be related to the increased radiant heat flux and temperature ranges above 1750 K. Furthermore, higher scattering of the heat flux distribution on the crucible surface could be determined indicating more uneven melt bath temperatures. Further research could focus on quantifying the total fuel consumption required for the heating up of the furnace, for which a transient numerical model could be developed. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Edition)

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Supplementary File 1 (ZIP, 2266 KiB)

17 pages, 5632 KiB  

Open AccessArticle

Preparation of Oxygen Reduction Catalyst Electrodes by Electrochemical Acidification and Synergistic Electrodeposition

by Liheng Zhou, Yongjian Guo, Yu Xu, Ping Li and Qi Zhang

Catalysts 2024, 14(5), 300; https://doi.org/10.3390/catal14050300 - 2 May 2024

Cited by 2 | Viewed by 1745

Abstract

A proton exchange membrane fuel cell (PEMFC) is an efficient and environmentally friendly power production technology that uses hydrogen energy. The cathodic oxygen reduction electrode is a critical component in the development of PEMFC. Most techniques deposit catalyst nanoparticles in areas that are [...] Read more.

A proton exchange membrane fuel cell (PEMFC) is an efficient and environmentally friendly power production technology that uses hydrogen energy. The cathodic oxygen reduction electrode is a critical component in the development of PEMFC. Most techniques deposit catalyst nanoparticles in areas that are inaccessible for catalytic processes, reducing platinum utilization. The substrate used in this study was carbon paper (CP) with a self-supporting structure. First, electrochemical acidification technology was employed to modify the CP’s surface, followed by nanoparticle manufacturing and fixation on the CP in a single step by electrodeposition. The Pt/C_0.5V_2.24CP catalyst electrode demonstrated high-quality activity in the oxygen reduction reaction (ORR), with a homogeneous particle dispersion and particle size of around 50 nm. The mass activity and electrochemical active surface area (ECSA) of the Pt/C_0.5V_2.24CP catalyst electrode were 1.74 and 3.98 times higher than those of the Pt/C/CP-1 electrodes made with commercial catalysts, respectively. After 5000 cycles of accelerated durability testing (ADT), the mass activity and ECSA were 1.28 times and 6.16 times more than Pt/C/CP-1. This paper successfully proved the viability of electrodepositing Pt nanoparticles on CP following acidification, and that the electrochemical acidification methods have a positive influence on improving electrode ORR activity. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Edition)

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31 pages, 1849 KiB  

Open AccessArticle

Applications of Oxyhydrogen, Direct Water Injection, and Early-Intake Valve Closure Technologies on a Petrol Spark Ignition Engine—A Path towards Zero-Emission Hydrogen Internal Combustion Engines

by Xiangtao Kong and Yaodong Wang

Energies 2024, 17(9), 2014; https://doi.org/10.3390/en17092014 - 24 Apr 2024

Cited by 1 | Viewed by 1354

Abstract

This study investigates the performance of a 4-MIX engine utilizing hydrogen combustion in pure oxygen, water injection, and the application of the early-intake valve closure (EIVC) Miller cycle. Transitioning from a standard petrol–oil mix to hydrogen fuel with pure oxygen combustion aims to [...] Read more.

This study investigates the performance of a 4-MIX engine utilizing hydrogen combustion in pure oxygen, water injection, and the application of the early-intake valve closure (EIVC) Miller cycle. Transitioning from a standard petrol–oil mix to hydrogen fuel with pure oxygen combustion aims to reduce emissions. Performance comparisons between baseline and oxyhydrogen engines showed proportional growth in the energy input rate with increasing rotational speed. The oxyhydrogen engine exhibited smoother reductions in brake torque and thermal efficiency as rotational speed increased compared to the baseline, attributed to hydrogen’s higher heating value. Water injection targeted cylinder and exhaust temperature reduction while maintaining a consistent injected mass. The results indicated a threshold of around 2.5 kg/h for the optimal water injection rate, beyond which positive effects on engine performance emerged. Investigation into the EIVC Miller cycle revealed improvements in brake torque, thermal efficiency, and brake specific fuel consumption as early-intake valve closure increased. Overall, the EIVC model exhibited superior energy efficiency, torque output, and thermal efficiency compared to alternative models, effectively addressing emissions and cylinder temperature concerns. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Edition)

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14 pages, 4497 KiB  

Open AccessArticle

Effects of Different Channel Geometries of Metallic Bipolar Plates on Proton Exchange Membrane Fuel Cell Performance

by Raquel Busqué, Matias Bossio, Albert Brigido and Antoni Lara

Energies 2023, 16(23), 7702; https://doi.org/10.3390/en16237702 - 22 Nov 2023

Cited by 4 | Viewed by 1821

Abstract

This paper investigates the effects of different channel geometries on the performance of Proton Exchange Membrane Fuel Cells (PEMFCs). The study employs computational fluid dynamics (CFD) coupled with thermal and electrochemical simulations to analyze five channel geometries (cases A to E) of bipolar [...] Read more.

This paper investigates the effects of different channel geometries on the performance of Proton Exchange Membrane Fuel Cells (PEMFCs). The study employs computational fluid dynamics (CFD) coupled with thermal and electrochemical simulations to analyze five channel geometries (cases A to E) of bipolar plates. A thorough study on this topic is not found in the literature and aims to identify designs that optimize performance and align with cost-effective production methods. Among the various studied geometries, case D, featuring a trapezoidal cross-section, exhibited the most favorable performance compared to the others, with a current density value of 2.01 A/cm² and a maximum temperature of 74.89 °C at 0.3 V, leading to an increase in generated power of 4.46%, compared to base case A. The trapezoidal shape enhanced the contact area with the reacting region, resulting in higher reaction rates and an improved overall performance. However, the study also highlights the relevance of velocity and turbulence, with case B demonstrating an enhanced performance due to its higher velocity, and case E benefiting from localized higher velocity regions and turbulence created by baffles. Case B can increase generated power at its peak by around 3.21%, and case E can improve it by 1.29%, with respect to case A. These findings underscore that contact area has a major impact on the PEMFC performance, but velocity and turbulence also play relevant roles. Additionally, trapezoidal channels can be easily manufactured through sheet metal-forming techniques, aligning well with new market trends of weight and cost reduction on bipolar plates. Fuel and oxygen utilization percentages, 38.14% and 62.96% at 0.3 V, respectively, further confirm the superiority of trapezoidal channels, providing insights into optimizing the PEMFC performance. This exhaustive study contributes valuable information for designing efficient metallic bipolar plates and advancing the development of practical fuel cell technologies. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Edition)

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31 pages, 3845 KiB  

Open AccessFeature PaperArticle

Educational Scale-Bridging Approach towards Modelling of Electric Potential, Electrochemical Reactions, and Species Transport in PEM Fuel Cell

by Ambrož Kregar, Klemen Zelič, Andraž Kravos and Tomaž Katrašnik

Catalysts 2023, 13(7), 1131; https://doi.org/10.3390/catal13071131 - 20 Jul 2023

Cited by 4 | Viewed by 2035

Abstract

The use of hydrogen fuel cells as a mobile source of electricity could prove key to the future decarbonisation of heavy-duty road and marine transportation. Due to the complex interplay of various physicochemical processes in fuel cells, further development of these devices will [...] Read more.

The use of hydrogen fuel cells as a mobile source of electricity could prove key to the future decarbonisation of heavy-duty road and marine transportation. Due to the complex interplay of various physicochemical processes in fuel cells, further development of these devices will depend on concerted efforts by researchers from various fields, who often lack in-depth knowledge of different aspects of fuel cell operation. These knowledge gaps can be filled by information that is scattered in a wide range of literature, but is rarely covered in a concise and condensed manner. To address this issue, we propose an educational-scale-bridging approach towards the modelling of most relevant processes in the fuel cell that aims to adequately describe the causal relations between the processes involved in fuel cell operation. The derivation of the model equations provides an intuitive understanding of the electric and chemical potentials acting on protons at the microscopic level and relates this knowledge to the terminology commonly used in fuel cell research, such as catalyst electric overpotential and internal membrane resistance. The results of the model agreed well with the experimental data, indicating that the proposed simple mathematical description is sufficient for an intuitive understanding of fuel cell operation. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Edition)

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19 pages, 4710 KiB  

Open AccessArticle

Experimental Investigation of Coupled Transport Mechanisms in a PEM Based Thermoelectric Energy Converter

by Maike Willke, Nils-Eric Rahm and Stephan Kabelac

Energies 2023, 16(14), 5434; https://doi.org/10.3390/en16145434 - 17 Jul 2023

Cited by 2 | Viewed by 1506

Abstract

Thermoelectric energy converters based on galvanic cells (TGC) offer the possibility of direct conversion of low-temperature waste heat into electrical energy and could therefore be a promising approach for an increase in the overall efficiency of energy conversion. Due to an externally applied [...] Read more.

Thermoelectric energy converters based on galvanic cells (TGC) offer the possibility of direct conversion of low-temperature waste heat into electrical energy and could therefore be a promising approach for an increase in the overall efficiency of energy conversion. Due to an externally applied heat source, a temperature gradient across the electrolyte is induced, leading to a gradient in the chemical potential of the species and an electrical potential difference between the electrodes. The aim of approaching an internal equilibrium state leads to various coupled molecular transport mechanisms taking place in the electrolyte, impacting the open circuit voltage (OCV) and the performance of the TGC. By applying the theory of non-equilibrium thermodynamics (NET) to describe these coupled processes, the interactions that occur can be characterized in more detail. In this work, a polymer electrolyte membrane (PEM)-based TGC with two H₂/H₂O electrodes of different temperatures and gas compositions is experimentally investigated. By controlling the gradients in temperature and concentration, different impacts on the resulting OCV can be identified. In addition, we present the measured coupling coefficient, representing the singular relation between the transport of the hydrogen ions inside the membrane and the electrical potential difference between the electrodes for a wide variety of working conditions. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Edition)

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Supplementary File 1 (ZIP, 1504 KiB)

18 pages, 3309 KiB  

Open AccessEditor’s ChoiceArticle

Effect of Fe on Calcined Ni(OH)₂ Anode in Alkaline Water Electrolysis

by Tae-Hyun Kim, Kee-Young Koo, Chu-Sik Park, Seong-Uk Jeong, Ji-Eun Kim, Su-Han Lee, Young-Ho Kim and Kyoung-Soo Kang

Catalysts 2023, 13(3), 496; https://doi.org/10.3390/catal13030496 - 28 Feb 2023

Cited by 5 | Viewed by 3291

Abstract

Ni (hydr)oxide is a promising and inexpensive material for oxygen evolution reaction (OER) catalysts and is known to dramatically increase the activity when used with Fe. Herein, we basified a Ni(II) solution and coated layered Ni(OH)₂ on Ni coins to prepare a [...] Read more.

Ni (hydr)oxide is a promising and inexpensive material for oxygen evolution reaction (OER) catalysts and is known to dramatically increase the activity when used with Fe. Herein, we basified a Ni(II) solution and coated layered Ni(OH)₂ on Ni coins to prepare a template with high stability and activity. To evaluate the stability and catalytic activity during high-current-density operation, we analyzed the electrochemical and physicochemical properties before and after constant current (CC) operation. The electrode with a Ni(OH)₂ surface exhibited higher initial activity than that with a NiO surface; however, after the OER operation at a high-current density, degradation occurred owing to structural destruction. The activity of the electrodes with a NiO surface improved after the CC operation because of the changes on the electrode-surface caused by the CC operation and the subsequent Fe incorporation from the Fe impurity in the electrolyte. After confirming the improvement in activity due to Fe, we prepared NiFe-oxide electrodes with improved catalytic activity and optimized the Ni precursor and Fe loading solution concentrations. The Ni-Fe oxide electrode prepared under the optimal concentrations exhibited an overpotential of 287 mV at a current density of 10 mA/cm², and a tafel slope of 37 mV dec⁻¹, indicating an improvement in the OER activity. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Edition)

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