Pure Hydrogen Research Articles

Underground Hydrogen Storage: Comparison of High-pressure Hydrogen, Liquid Hydrogen, and Ammonia

One of the alternatives for effective storage of irregularly produced renewable energy is hydrogen energy. In order to realize a hydrogen-based society, not only environmentally friendly production of hydrogen but also effective storage is very important. Underground hydrogen storage technology is a technology that has evolved from the technology for storing natural gas underground, and includes waste gas fields, salt domes, aquifers, and rock cavities. When stored underground, hydrogen is converted into high-pressure gaseous hydrogen, liquefied hydrogen, and ammonia. Liquefied hydrogen requires extremely low storage temperatures, and ammonia is a toxic substance that requires separate handling, and energy loss occurs during the conversion process. To compensate for this, research on liquefied hydrogen, such as multilayer insulation technology, is being conducted. Ammonia has successfully extracted high-purity hydrogen by developing a membrane reactor. Ammonia toxicity can be prevented by strengthening leak detection and blocking facilities. Among these, ammonia was found to be the most suitable for underground storage in terms of economic feasibility, environment, and commercialization.

Fe–Ce–Al Catalysts for Decomposition of Methane to High Purity Hydrogen and High-Value Carbon

Fe–Ce–Al Catalysts for Decomposition of Methane to High Purity Hydrogen and High-Value Carbon

Mechanical Properties and Microstructural Characteristics of Steel Pipes after Long-Time Hydrogen Exposure

There are three possibilities to transport hydrogen by high pressure pipeline (i) blending hydrogen into the existing natural gas pipeline system, (ii) after checking the integrity, using the natural gas transporting pipeline system to transport hydrogen, (iii) building a new pipeline system to transport pure hydrogen. In all three cases should be known the behaviour of the pipe material and its welded joints influenced under high pressure hydrogen. For this aim pipeline sections made of P355NH base material were investigated without and with hydrogen exposure, where the exposure time was 41 days. Gas metal arc welding and hybrid tungsten arc welding / gas metal arc welding were applied for preparation of the girth weld joints. Tensile, three point bending and hardness tests, furthermore microstructural investigations were performed both on base materials and girth welds of the pipeline sections. The testing results were analysed and compared with each other (base material vs. welded joints, without exposure vs. with exposure) and with limit values can be found in the literature. Conclusions were drawn on the behaviour of the investigated pipe material and its welded joints.

Exploring the benefits of hydrogen-water injection technology in internal combustion engines: A rigorous experimental study

Previous hydrogen researchers have demonstrated the great potential of hydrogen as a zero-carbon fuel and its wider operational ability to directly replace the existing fossil-fuelled internal combustion engines (ICE). Hydrogen direct-injection technology can operate at stoichiometric combustion conditions, fully eliminating the intake backfire phenomena, which has the benefit of low airflow requirements and is a suitable solution for naturally aspirated ICE platforms. However, significant challenges must be addressed when operating an H2 ICE at or near stoichiometric. These include rapid pressure rise rate, high in-cylinder gas pressure and temperature and the consequential higher engine-out NOx emissions. This study provides a comprehensive experimental analysis of the effect of water injection on a light-duty H2 engine’s performance, efficiency, burn durations and NOx emission. The engine was modified to operate with hydrogen via a centrally-mounted direct H2 injector and an intake port-mounted water injection system. The study included water vapour measurements, NOx concentrations and other exhaust gases. The practical implications of these findings are significant. The results demonstrated that the NOx emissions were reduced by 79% when the water was injected at a rate of 5 kg/h at 10 bar IMEP and 2000 rpm. This reduction in emissions, coupled with the observed decrease in cylinder pressure and the rate of pressure rise, could substantially improve engine performance and efficiency. At higher load regions, the water injection extended the maximum engine load to 24 bar IMEP and increased the engine torque output by 10%. The maximum Indicated Thermal Efficiency (ITE) increased from 41% at 16.5 bar IMEP to 42.5% at 18 bar IMEP at a lower lambda, with a corresponding reduction in the intake-air-boost pressure requirement. Of particular note, the use of water injection decreased the engine-out NOx emissions under high-load conditions by more than 55%, even at richer AFR compared to pure hydrogen operation.

Optimization of power performance and combustion stability of ultra-lean combustion in hydrogen fuel engines through combined turbulent jet ignition and variable valve timing

Although pure hydrogen engines can achieve zero carbon and extremely low NOx emissions under ultra-lean combustion conditions, there are limitations with combustion stability and power performance. This paper combines turbulent jet ignition (TJI) and variable valve timing (VVT) technology, which not only improves the power output of pure hydrogen engines under ultra-lean combustion conditions but also ensures the engine’s stable operation. Therefore, this research reveals the working characteristics of TJI engines under lean conditions through numerical methods and explores the optimization characteristics of VVT on engine power performance and stability through experiments. The results indicate that TJI utilizes strong turbulence and multiple-point ignition to improve the efficiency of the mixture and combustion speed, ensuring reliable ignition capability under ultra-lean operating and achieving a stable and effective combustion process. According to the experimental results, the combination of TJI with VVT technology can ensure engine cyclic-variability of less than 1.5 % and the maximum values of Brake mean effective pressure (BMEP) and Brake thermal efficiency (BTE) are 4.5 bar and 41.6 %, respectively. This innovative technology combination not only enables the efficient and eco-friendly development of the transportation industry but also holds significant importance for promoting carbon-free fuels and environmental protection in the future.

Dynamic Fe-O-Cu induced electronic structure modulation on CuOx electrode for selective electrocatalytic oxidation of glycerol

Electrocatalytic glycerol oxidation reaction to produce high-value organic chemicals has research significance for managing the overproduction of glycerol and handling the energy crisis. Herein, a copper-based self-supporting catalytic electrode with a dynamic Fe-O-Cu optimized coordination (Fe-CuOx/CF) was prepared. The oxygen-bridged asymmetric coordination structure (Fe-O-Cu) optimized the electronic configuration and promoted the formation of the crucial intermediate species. After Fe was embedded in the lattice of copper oxides, a remarkable enhancement in the adsorption capacity of OH- and glycerol was confirmed. As a result, Fe-CuOx/CF exhibited an excellent production capacity of formate, with high faradaic efficiency and selectivity values of 93.65 % and 95.10 %. Concurrent production of formate and high purity hydrogen was achieved in the double-electrode flow electrolyzer. This work provides guiding significance for the optimization of the catalytic coordination and the design of high-efficiency transition metal-based catalysts for electrooxidation of biomass platform molecules.

Comparative Hydrogen Production Routes via Steam Methane Reforming and Chemical Looping Reforming of Natural Gas as Feedstock

Hydrogen production is essential in the transition to sustainable energy. This study examines two hydrogen production routes, steam methane reforming (SMR) and chemical looping reforming (CLR), both using raw natural gas as feedstock. SMR, the most commonly used industrial process, involves reacting methane with steam to produce hydrogen, carbon monoxide, and carbon dioxide. In contrast, CLR uses a metal oxide as an oxygen carrier to facilitate hydrogen production without generating additional carbon dioxide. Simulations conducted using Aspen HYSYS analyzed each method’s performance and energy consumption. The results show that SMR achieved 99.98% hydrogen purity, whereas CLR produced 99.97% purity. An energy analysis revealed that CLR requires 31% less energy than SMR, likely due to the absence of low- and high-temperature water–gas shift units. Overall, the findings suggest that CLR offers substantial advantages over SMR, including lower energy consumption and the production of cleaner hydrogen, free from carbon dioxide generated during the water–gas shift process.

Perforation design coupled with heterogeneity during underground hydrogen storage in steeply dipping anticline aquifers

Hydrogen has been recognized as a crucial energy carrier to reduce greenhouse gas emissions. However, as it is not always possible to meet current energy demands, underground hydrogen storage (UHS) is required for energy supply and consumption. UHS is an emerging field of study with limited investigations regarding structural conditions and wellbore perforation design in steeply dipping anticline aquifers. This study investigates different perforation schemes with respect to UHS within steeply dipping anticline aquifers to find the most suitable injection/production design while examining small-scale reservoir heterogeneities. Several UHS improvement techniques are evaluated, including water and CO2 injection through flank wells during hydrogen production. The results indicate that the highest hydrogen production is achieved with a fully perforated H2 well located at the crest as it provides the maximum contact between the hydrogen and aquifer layers during H2 injection/production. In contrast, hydrogen production is diminished with increased heterogeneity, as higher heterogeneities raise the chance of H2 being trapped. To enhance UHS performance, first H2 initialization before UHS beginning was evaluated but the results showed that it does not enhance UHS performance in a steeply dipped anticline aquifers, as effectively as it does in gas reservoirs. Water injection from flank wells during H2 production cycles showed improvement in hydrogen withdrawal, while water production experienced a slight increase. CO2 injection from flank wells was evaluated to effectively increase H2 recovery as a cushion gas and to maintain hydrogen purity during production. According to results, hydrogen purity was not affected only in high heterogeneity, since more hydrogen gets trapped in the small-scale high heterogeneity level, which prevents the mixing zone from reaching the H2 well during production. While the method prevents hydrogen contamination in anticline aquifers due to the high dip angle coupled with high heterogeneity levels, it leads to a lower hydrogen recovery.

Computational Fluid Dynamics Modelling of Hydrogen Production via Water Splitting in Oxygen Membrane Reactors.

The utilization of oxygen transport membranes enables the production of high-purity hydrogen by the thermal decomposition of water below 1000 °C. This process is based on a chemical potential gradient across the membrane, which is usually achieved by introducing a reducing gas. Computational fluid dynamics (CFD) can be used to model reactors based on this concept. In this study, a modelling approach for water splitting is presented in which oxygen transport through the membrane acts as the rate-determining process for the overall reaction. This transport step is implemented in the CFD simulation. Both gas compartments are modelled in the simulations. Hydrogen and methane are used as reducing gases. The model is validated using experimental data from the literature and compared with a simplified perfect mixing modelling approach. Although the main focus of this work is to propose an approach to implement the water splitting in CFD simulations, a simulation study was conducted to exemplify how CFD modelling can be utilized in design optimization. Simplified 2-dimensional and rotational symmetric reactor geometries were compared. This study shows that a parallel overflow of the membrane in an elongated reactor is advantageous, as this reduces the back diffusion of the reaction products, which increases the mean driving force for oxygen transport through the membrane.

Sustainable hydrogen production with synergistic electron transfer enhancement in nickel-based alkaline HER electrocatalyst empowered by graphene oxide

The hydrogen evolution reaction (HER) plays a crucial role in driving forward the transition to a hydrogen-based economy by providing a means to generate pure hydrogen. However, the efficient and cost-effective production of hydrogen via HER faces significant challenges, particularly at the cathode. To address these challenges, we produced a hybrid material – 2D graphene oxide (GO) sheets coated onto nickel sulfide (NiS) microspheres anchored on Ni Foam (GO@NiS/Ni Foam) using a straightforward synthesis technique. Our research highlights the significant influence of the interaction between GO and NiS on the performance of HER, attributed to the enhancement of electron transport at the interface. Furthermore, the GO@NiS/Ni Foam composite exhibits remarkable durability over extended periods, maintaining its superior functionality for up to 40 h of continuous operation. This underscores its potential for practical implementation in efficient water-splitting processes, offering a promising solution to the challenges hindering widespread adoption of hydrogen technology.

Recent development of non‐iridium‐based electrocatalysts for acidic oxygen evolution reaction

AbstractProton exchange membrane water electrolyser (PEMWE) possesses great significance for the production of high purity of hydrogen. To expedite the anodic oxygen evolution reaction (OER) that involved multiple electron–proton‐coupled process, efficient and stable electrocatalysts are highly desired. Currently, noble‐metal Ir‐based materials are the benchmark anode due to its corrosion‐resistant property and favourable combination of activity/stability. However, the large‐scale deployment of PEMWE is usually constrained due to the use of the scarcest element iridium. In this review, we disclose the current research progress towards the non‐iridium‐based electrocatalysts for OER in acidic media, and then summarize some typical oxides that possesses good catalytic performance. Besides, we also present the unresolved problems and challenges in an attempt to enhance the activity/stability of these catalysts.

Tuneable mesoporous silica material for hydrogen storage application via nano-confined clathrate hydrate construction

Safe storage and utilisation of hydrogen is an ongoing area of research, showing potential to enable hydrogen becoming an effective fuel, substituting current carbon-based sources. Hydrogen storage is associated with a high energy cost due to its low density and boiling point, which drives a high price. Clathrates (gas hydrates) are water-based (ice-like) structures incorporating small non-polar compounds such as H2 in cages formed by hydrogen bonded water molecules. Since only water is required to construct the cages, clathrates have been identified as a potential solution for safe storage of hydrogen. In bulk, pure hydrogen clathrate (H2O-H2) only forms in harsh conditions, but confined in nanospaces the properties of water are altered and hydrogen storage at mild pressure and temperature could become possible. Here, specifically a hydrophobic mesoporous silica is proposed as a host material, providing a suitable nano-confinement for ice-like clathrate hydrate. The hybrid silica material shows an important decrease of the pressure required for clathrate formation (approx. 20%) compared to the pure H2O-H2 system. In-situ inelastic neutron scattering (INS) and neutron diffraction (ND) provided unique insights into the interaction of hydrogen with the complex surface of the hybrid material and demonstrated the stability of nano-confined hydrogen clathrate hydrate.

The Influence of Helium Addition on the Combustion Process in a Hydrogen-Fueled Turbulent Jet Ignition Engine

There are considerably fewer requirements for the quality of hydrogen combusted in an engine than its quality for fuel cells. Therefore, the analysis was carried out on the combustion of hydrogen–helium mixtures in an engine with a two-stage combustion system (TJI—Turbulent Jet Ignition). A single-cylinder research engine with a passive and active prechamber was used. A hydrogen–helium mixture was supplied to the main chamber in proportions of 100:0, 90:10, 80:20, 30:70, and 60:40 volume fractions. The prechamber was fueled only with pure hydrogen. Combustion was carried out in the lean charge range (λ = 1.5–3) and at a constant value of the Center of Combustion (CoC = 8–10 deg aTDC). It was found that the helium concentration in the mixture affected the changes in combustion pressure, heat release rate and the amount of heat release. It was observed that increasing the proportion of helium in the mixture by 10% also reduces the IMEP by approximately 10% and reduces the rate of heat release by approximately 20%. In addition, helium influences knock combustion. Limits of MAPO = 1 bar mean assumed that knock combustion occurs in the main chamber at values of λ < 1.9. Increasing the excess air ratio results in a gradual reduction in the temperature of the exhaust gas, which has a very rapid effect on changes in the concentration of nitrogen oxides. Studies carried out on the helium addition in hydrogen fuel indicate that it is possible to use such blends with a partial deterioration of the thermodynamic properties of the two-stage combustion process.

Novel Roles of Catalysts in Producing High-purity High-pressure Hydrogen from Sodium Borohydride.

Hydrogen has received enormous attention as a clean fuel with its high specific energy (142 MJ/kg). To apply hydrogen as a practically available energy vector, the direct production of high-pressure hydrogen with high purity is pivotal, as it allows for circumventing the mechanical compression process. Recently, the concept of utilizing sodium borohydride (SBH) dehydrogenation as a chemical compressor that can generate high-pressure hydrogen gas was demonstrated by adopting formic acid as an acid catalyst. However, the presence of impurities (e.g., CO, CO2) in the final gas product requires an alternative method to enhance the use of SBH as a chemical compressor. Here, we highlighted the feasibility of producing high-purity, high-pressure hydrogen gas from the SBH dehydrogenation with and without Co-based catalysts. The scrutiny behind the thermodynamics and kinetics of the SBH dehydrogenation was conducted under the elevated pressure condition. As a result, the dual roles of the catalysts as proton collectors and heat sources were revealed, both of which are essential for improving hydrogen production efficiency. We hope that our research stimulates subsequent research that pave the way to exploit hydrogen as an energy vector and achieve a more sustainable future society.

Evaluating the Effect of Blended and Pure Hydrogen in X60 Pipeline Steel for Low-Pressure Transmission Using Hollow-Specimen Slow-Strain-Rate Tensile Testing

Evaluating the Effect of Blended and Pure Hydrogen in X60 Pipeline Steel for Low-Pressure Transmission Using Hollow-Specimen Slow-Strain-Rate Tensile Testing

NiCo2O4-based wool-ball as an electrocatalyst for methanol assisted water splitting, an alternative to water splitting

Hydrogen energy is considered a potential solution to the energy crisis and environmental pollution concerns. Pure hydrogen can be produced from electrochemical water splitting, however, the oxygen evolution reaction (OER) is the primary obstacle due to its sluggish reaction kinetics. Introducing methanol oxidation is one possible solution to replace OER for water splitting to produce hydrogen as an energy source. In this article, a NiCo₂O₄-based wool-ball electrocatalyst was prepared via a solvothermal process followed by annealing. The catalyst showed high purity and a wool-ball structure, where the threads are arranged in different patterns and composed of sub-nano-sized spheres. The catalyst exhibited an excellent response to oxidation reactions and reduced severely the potential for 250 mV, when 1.17 mM of methanol was introduced into a 1 M KOH solution. The catalyst also demonstrated good performance for the hydrogen evolution reaction (HER), however, there was a reduction in performance in the presence of methanol. This might be due to the formation of a methanol layer that inhibits the HER in the KOH solution, as methanol does not participate in HER. This resistance was confirmed with electrochemical impedance spectroscopy (EIS) and electrochemical surface area (ECSA) measurements, where the ECSA value in KOH was 4.10, which reduced to 2.63 in the presence of methanol. The catalyst exhibited excellent stability for both HER and methanol oxidation reaction (MOR) over a long duration of 3600 s.

Automated Optimization of a Multistep, Multiphase Continuous Flow Process for Pharmaceutical Synthesis.

Flow synthesis is becoming increasingly relevant as a sustainable and safe alternative to traditional batch processes, as reaction conditions that are not usually achievable in batch chemistry can be exploited (for example, higher temperatures and pressures). Telescoped continuous reactions have the potential to reduce waste by decreasing the number of separate unit operations (e.g., crystallization, filtration, washing, and drying), increase safety due to limiting operator interaction with potentially harmful materials that can be reacted in subsequent steps, minimize supply chain disruption, and reduce the need to store large inventories of intermediates as they can be synthesized on demand. Optimization of these flow processes leads to further efficiency when exploring new reactions, as with a higher yield comes higher purity, reduced waste, and a greener synthesis. This project explored a two-step process consisting of a three-phase heterogeneously catalyzed hydrogenation followed by a homogeneous amidation reaction. The steps were optimized individually and as a multistep telescoped process for yield using remote automated control via a Bayesian optimization algorithm and HPLC analysis to assess the performance of a reaction for a given set of experimental conditions. 2-MeTHF was selected as a green solvent throughout the process, and the heterogeneous step provided good atom economy due to the use of pure hydrogen gas as a reagent. This research highlights the benefits of using multistage automated optimization in the development of pharmaceutical syntheses. The combination of telescoping and optimization with automation allows for swift investigation of synthetic processes in a minimum number of experiments, leading to a reduction in the number of experiments performed and a large reduction in process mass intensity values.

Investigation of the Antibacterial Properties of Janus Micromotors Catalytic Propelled by Manganese Dioxide and Hydrogen Peroxide to Reduce Bacterial Density.

Between 2015 and 2017, 90% of Chinese adults were reported to have periodontitis of varying degrees, highlighting the importance of novel, inexpensive, and affordable treatments for the public. The fact that more and more pathogens are becoming resistant to antibiotics further highlights this prevalence. This article addresses a novel micromotor capable of generating reactive oxygen species, as proven by a Fenton-like reaction. Such reactions allow the targeting of Gram-negative bacteria such as Escherichia coli, which are eliminated order of magnitude more effectively than by pure hydrogen peroxide, thereby addressing pathogens relevant in oral infections. The basis of the micromotors, which generate reactive oxygen species on site, reduces the likelihood of resistance developing in these types of bacteria. Catalytically reducing hydrogen peroxide in this process, these micromotors propel themselves forward. This proof of principle study paves the way for the utilization of micromotors in the field of skin disinfection utilizing hydrogen peroxide concentrations which were in previous works proven noncytotoxic.

Study on the flame structure and flow field of hydrogen-enriched combustion in array micro-tube

Addressing climate change and reducing greenhouse gas emissions are critical priorities. Utilizing hydrogen-rich methane or pure hydrogen as fuels within gas turbines, facilitated by array micro-tube premixed combustion technology, is anticipated to markedly accelerate the decarbonization process of the energy sector. In this study, the flame structure of the array micro-tube premixed burner under various fuel compositions was examined using OH-Planar Laser-Induced Fluorescence and Particle Image Velocimetry measurement techniques. The effects of the equivalence ratio (φ) and the hydrogen power ratio (HPR) on the characteristics of the flame front, including its curvature, density, volume, and the associated flow field properties, were discussed. As φ and HPR increase, the wrinkled structure of the flame front is significantly enhanced, with a more pronounced effect on smaller scales. This enhancement leads to the separation of the unburned pockets from the main flame. Concurrently, both the flame length and the flame area decrease with the augmentation of φ and HPR, indicating a more concentrated combustion process and increased combustion intensity under hydrogen-enriched and pure hydrogen conditions. The study also observed a slight increase in both the negative and positive curvatures of the flame front, with a more notable increase in the negative curvature. The increased negative curvature results in an elevated degree of wrinkling and a higher value of Σ (flame surface density), reaching a maximum of 0.876 mm−1 under the conditions where φ is 0.8 and ⟨c⟩ (mean progress variable) is 0.5, resulting in the smallest observed flame volume of 100.6 mm3. Upon coupling the flame with the flow field, it was discovered that the exit flow field of the array micro-tube exhibits symmetry and a characteristic conical flame shape. The burning velocity of the side flame brushes increases, and the velocity peak shifts upstream. The aforementioned findings confirm that the addition of hydrogen increases the laminar flame velocity, enabling the flame to stably anchor to the microtube outlet and thereby enhance the flame's robustness and stability.

Effect of ammonia reforming on combustion and emission characteristics of a 4-valve engine with an active pre-chamber

Ammonia (NH3), as a hydrogen carrier and carbon-free fuel, offers an attractive opportunity for engines to achieve carbon neutrality. Turbulent jet ignition (TJI) combined with ammonia reforming shows the great capacity in ammonia-fueled engines. In this study, the effects of reforming strategy in an ammonia-fueled TJI are numerically studied, addressing the reforming ratio and reforming region. The results show that when only using reformate in the pre-chamber, the promoting effect of jet flame is more effective on the initial combustion phase. There are still very high NH3 emissions due to the low reactivity in the main chamber. Further using reformate both in the pre-chamber and the main chamber, all the combustion stages (ST-CA10, CA10-50, CA50-90) can be shortened almost linearly with the increase of reforming ratio. Besides, the unburned NH3 can be reduced to an acceptable level when the reforming ratio reaches 200‰ (hydrogen energy ratio of 18.50%). The main reason is that the jet-induced strong flow field is coincident with the whole combustion stage. Further increasing the reforming ratio (pure hydrogen) in the pre-chamber, a high combustion efficiency and acceptable NH3 emission can be achieved at a low hydrogen energy ratio (7.08%). However, knocking combustion will happen at high reforming ratio with a low knock intensity. The results can provide some guidance for making the best-promoting benefit of the limited hydrogen in ammonia TJI engines with different reforming strategies.