Korea, Republic of
Analysis of Hydrogen Filling of 175 Liter Tank for Large-Sized Hydrogen Vehicle
May 2022
Publication
Due to the low density of hydrogen gas under ambient temperature and atmospheric pressure conditions the high-pressure gaseous hydrogen storage method is widely employed. With high-pressure characteristics of hydrogen storage rigorous safety precautions are required such as filling of compressed gas in a hydrogen tank to achieve reliable operational solutions. Especially for the large-sized tanks (above 150 L) safety operation of hydrogen storage should be considered. In the present study the compressed hydrogen gas behavior in a large hydrogen tank of 175 L is investigated for its filling. To validate the numerical approach used in this study numerical models for the adaptation of the gas and turbulence models are examined. Numerical parametric studies on hydrogen filling for the large hydrogen tank of 175 L are conducted to estimate the hydrogen gas behavior in the hydrogen tank under various conditions of state of charge of pressure and ambient temperature. From the parametric studies the relationship between the initial SOC pressure condition and the maximum temperature rise of hydrogen gas was shown. That is the maximum temperature rise increases as the ambient temperature decreases and the rise increases as the SOC decreases.
Charpy Impact Properties of Hydrogen-Exposed 316L Stainless Steel at Ambient and Cryogenic Temperatures
May 2019
Publication
316L stainless steel is a promising material candidate for a hydrogen containment system. However when in contact with hydrogen the material could be degraded by hydrogen embrittlement (HE). Moreover the mechanism and the effect of HE on 316L stainless steel have not been clearly studied. This study investigated the effect of hydrogen exposure on the impact toughness of 316L stainless steel to understand the relation between hydrogen charging time and fracture toughness at ambient and cryogenic temperatures. In this study 316L stainless steel specimens were exposed to hydrogen in different durations. Charpy V-notch (CVN) impact tests were conducted at ambient and low temperatures to study the effect of HE on the impact properties and fracture toughness of 316L stainless steel under the tested temperatures. Hydrogen analysis and scanning electron microscopy (SEM) were conducted to find the effect of charging time on the hydrogen concentration and surface morphology respectively. The result indicated that exposure to hydrogen decreased the absorbed energy and ductility of 316L stainless steel at all tested temperatures but not much difference was found among the pre-charging times. Another academic insight is that low temperatures diminished the absorbed energy by lowering the ductility of 316L stainless steel
A Comprehensive Review of Microbial Electrolysis Cells (MEC) Reactor Designs and Configurations for Sustainable Hydrogen Gas Production
Nov 2015
Publication
Hydrogen gas has tremendous potential as an environmentally acceptable energy carrier for vehicles. A cutting edge technology called a microbial electrolysis cell (MEC) can achieve sustainable and clean hydrogen production from a wide range of renewable biomass and wastewaters. Enhancing the hydrogen production rate and lowering the energy input are the main challenges of MEC technology. MEC reactor design is one of the crucial factors which directly influence on hydrogen and current production rate in MECs. The rector design is also a key factor to upscaling. Traditional MEC designs incorporated membranes but it was recently shown that membrane-free designs can lead to both high hydrogen recoveries and production rates. Since then multiple studies have developed reactors that operate without membranes. This review provides a brief overview of recent advances in research on scalable MEC reactor design and configurations.
Multi-Period Planning of Hydrogen Supply Network for Refuelling Hydrogen Fuel Cell Vehicles in Urban Areas
May 2020
Publication
The hydrogen economy refers to an economic and industrial structure that uses hydrogen as its main energy source replacing traditional fossil-fuel-based energy systems. In particular the widespread adoption of hydrogen fuel cell vehicles (HFCVs) is one of the key factors enabling a hydrogen economy and aggressive investment in hydrogen refuelling infrastructure is essential to make large-scale adoption of HFCVs possible. In this study we address the problem of effectively designing a hydrogen supply network for refuelling HFCVs in urban areas relatively far from a large hydrogen production site such as a petrochemical complex. In these urban areas where mass supply of hydrogen is not possible hydrogen can be supplied by reforming city gas. In this case building distributed hydrogen production bases that extract large amounts of hydrogen from liquefied petroleum gas (LPG) or compressed natural gas (CNG) and then supply hydrogen to nearby hydrogen stations may be a cost-effective option for establishing a hydrogen refuelling infrastructure in the early stage of the hydrogen economy. Therefore an optimization model is proposed for effectively deciding when and where to build hydrogen production bases and hydrogen refuelling stations in an urban area. Then a case study of the southeastern area of Seoul known as a commercial and residential center is discussed. A variety of scenarios for the design parameters of the hydrogen supply network are analyzed based on the target of the adoption of HFCVs in Seoul by 2030. The proposed optimization model can be effectively used for determining the time and sites for building hydrogen production bases and hydrogen refuelling stations.
MELCOR Analysis of a SPARC Experiment for Spray-PAR Interaction During a Hydrogen Release
Oct 2020
Publication
A series of experiments were performed in the SPARC (spray-aerosol-recombiner-combustion) test facility to simulate a hydrogen mitigation system with the actuation of a PAR (passive auto-catalytic re-combiner) and spray system. In this study the SPARC-SPRAY-PAR (SSP1) experiment is chosen to benchmark the MELCOR (a lumped-parameter code for severe accident analysis) predictions against test data. For this purpose firstly we prepared the base input model of the SPARC test vessel and tested it by a simple verification problem with well-defined boundary conditions. The implementation of a currently used PAR correlation in MELCOR is shown to be appropriate for the simulation of a PAR actuation experiment. In an SSP1 experiment the PAR is reacting with hydrogen and the spray actuation starts as soon as hydrogen injection is complete. The MELCOR simulation well predicts the pressure behavior and the gas flow affected by operating both a PAR and spray system. However the local hydrogen concentration measurement near the inlet nozzle is much higher than the volume average-value by MELCOR since high jet flow from the nozzle is dispersed in the corresponding cell volume. The experimental reproduction of the phenomena we expect or conversely the identification of phenomena we do not understand will continue to support the verification of analytical models using experimental data and to analyze the impact of spray on PAR operations in severe accident conditions.
South Korea’s Big Move to Hydrogen Society
Nov 2020
Publication
Extensive energy consumption has become a major concern due to increase of greenhouse gas emissions and global warming. Hence hydrogen has attracted attention as a green fuel with zero carbon emission for green transportation through production of electric vehicles with hydrogen fuel cells. South Korea has launched a hydrogen society policy with the objective of expanding production of hydrogen from renewable energy sources. The hydrogen economy will play a critical role in reducing atmospheric pollution and global arming. However new development of infrastructure for hydrogen refuelling and increasing awareness of the hydrogen economy is required together with reduced prices of hydrogen-driven vehicles that are promising options for a sustainable green hydrogen economy.
Review of the Durability of Polymer Electrolyte Membrane Fuel Cell in Long-Term Operation: Main Influencing Parameters and Testing Protocols
Jul 2021
Publication
Durability is the most pressing issue preventing the efficient commercialization of polymer electrolyte membrane fuel cell (PEMFC) stationary and transportation applications. A big barrier to overcoming the durability limitations is gaining a better understanding of failure modes for user profiles. In addition durability test protocols for determining the lifetime of PEMFCs are important factors in the development of the technology. These methods are designed to gather enough data about the cell/stack to understand its efficiency and durability without causing it to fail. They also provide some indication of the cell/stack’s age in terms of changes in performance over time. Based on a study of the literature the fundamental factors influencing PEMFC long-term durability and the durability test protocols for both PEMFC stationary and transportation applications were discussed and outlined in depth in this review. This brief analysis should provide engineers and researchers with a fast overview as well as a useful toolbox for investigating PEMFC durability issues.
Optimal Facility Combination Set of Integrated Energy System Based on Consensus Point between Independent System Operator and Independent Power Producer
Dec 2022
Publication
In recent years the frequency of power demand imbalance and negative price phenomenon has risen due to the rapid expansion of renewable energy sources (RES). Because of this a means to reduce the curtailment of RES by utilizing surplus energy is essential. This paper focuses on reducing the curtailment of wind turbines (WT) with high output intermittency and minimizing the investment cost of IES via an integrated energy system (IES). The IES operation seeks to improve the acceptability and efficiency of the RES as it supports the integration of various energies mix such as electricity heat hydrogen. This paper proposes an optimal facility combination set (FCS) of IES that satisfies the requirements of ISO and IPP using Multi-Objective Optimization Programming (MOP). The case study is based on a wind farm in South Korea set in Aewol-eup Jeju-Island. The case study results provide the best configuration of the IES energy mix with the best economic value and efficiency while satisfying ISO and IPP perspectives.
A Study on the Joule-Thomson Effect of During Filling Hydrogen in High Pressure Tank
Dec 2022
Publication
With the development of the hydrogen fuel cell automobile industry higher requirements are put forward for the construction of hydrogen energy infrastructure the matching of parameters and the control strategy of hydrogen filling rate in the hydrogenation process of hydrogenation station. Fuel for hydrogen fuel cell vehicles comes from hydrogen refueling stations. At present the technological difficulty of hydrogenation is mainly reflected in the balanced treatment of reducing the temperature rise of hydrogen and shortening the filling time during the fast filling process. The Joule-Thomson (JT) effect occurs when high-pressure hydrogen gas passes through the valve assembly which may lead to an increase in hydrogen temperature. The JT effect is generally reflected by the JT coefficient. According to the high pressure hydrogen in the pressure reducing valve the corresponding JT coefficients were calculated by using the VDW equation RK equation SRK equation and PR equation and the expression of JT effect temperature rise was deduced which revealed the hydrogen temperature variation law in the process of reducing pressure. Make clear the relationship between charging parameters and temperature rise in the process of decompression; the flow and thermal characteristics of hydrogen in the process of decompression are revealed. This study provides basic support for experts to achieve throttling optimization of related pressure control system in hydrogen industry
Scenario-Based Techno-Economic Analysis of Steam Methane Reforming Process for Hydrogen Production
Jun 2021
Publication
Steam methane reforming (SMR) process is regarded as a viable option to satisfy the growing demand for hydrogen mainly because of its capability for the mass production of hydrogen and the maturity of the technology. In this study an economically optimal process configuration of SMR is proposed by investigating six scenarios with different design and operating conditions including CO2 emission permits and CO2 capture and sale. Of the six scenarios the process configuration involving CO2 capture and sale is the most economical with an H2 production cost of $1.80/kg-H2. A wide range of economic analyses is performed to identify the tradeoffs and cost drivers of the SMR process in the economically optimal scenario. Depending on the CO2 selling price and the CO2 capture cost the economic feasibility of the SMR-based H2 production process can be further improved.
Study on Behavior of Ambient Hydraulic Cycling Test for 70 MPA Type-3 Hydrogen Composite Cylinder
Sep 2013
Publication
Hydrogen used in hydrogen fuel cell vehicles is the flammable gas which has wide flammable range and flame propagation speed is very fast. This fuel cell vehicle equipped with high-pressure vessel in the form of fuel to supply the high pressure hydrogen storage system needs to be checked carefully about a special safety design and exact weak point for high pressure repeated fatigue. 70 L liner and 70 MPa Type-3 vessel were tested using the equipments which can perform ambient hydraulic cycling test and burst test in the Korea Gas Safety Corporation. And it was performed to identify the internal external behaviour through the Finite Element Analysis (FEA) and real leakage mode for high pressure repeated fatigue when subjected to be pressurized in vessel. 70 L liner and 70 MPa Type-3 vessel were tested using the equipments which can perform ambient hydraulic cycling test and burst test in the Korea Gas Safety Corporation. And it was performed to identify the internal external behaviour through the Finite Element Analysis (FEA) and real leakage mode for high pressure repeated fatigue when subjected to be pressurized in vessel. Through this study liner of type-3 hydrogen vessel is ruptured first on cylindrical (body) part than Dome part in 8.5 MPa. Also the same Phenomena are confirmed through the Finite Element Analysis (FEA). External composite leakage mode in ambient hydraulic cycling test was occurred in different area such as the Dome Dome knuckle and cylindrical (body) parts. But cracks of inner liner for gas tight were occurred in only cylindrical (body) parts. Also in FEA results when vessel is pressurized Dome knuckle and cylindrical (body) parts is weakest among all parts because of expansion of cylindrical (body) parts.
Advanced Sizing Methodology for a Multi-Mode eVTOL UAV Powered by a Hydrogen Fuel Cell and Battery
Jan 2022
Publication
A critical drawback of battery-powered eVTOL UAVs is their limited range and endurance and this drawback could be solved by using a combination of hydrogen fuel cells and batteries. The objective of this paper is to develop a sizing methodology for the lift+cruise-type eVTOL UAV powered by a hydrogen fuel cell and battery. This paper presents the constraints analysis method for forward flight/VTOL multi-mode UAV the regression model for electric propulsion system sizing a sizing method for an electric propulsion system and hydrogen fuel cell system and a transition analysis method. The total mass of the UAV is iteratively calculated until convergence and the optimization method is used to ensure that the sizing results satisfy the design requirements. The sizing results are the UAV’s geometry mass and power data. To verify the accuracy of the proposed sizing methodology the sizing and the conceptual design phase results of a 25 kg hydrogen fuel-cell-powered UAV are compared. All parameters had an error within 10% and satisfied the design requirements.
Prediction of Hydrogen Concentration in Containment During Severe Accidents Using Fuzzy Neural Network
Jan 2015
Publication
Recently severe accidents in nuclear power plants (NPPs) have become a global concern. The aim of this paper is to predict the hydrogen buildup within containment resulting from severe accidents. The prediction was based on NPPs of an optimized power reactor 1000. The increase in the hydrogen concentration in severe accidents is one of the major factors that threaten the integrity of the containment. A method using a fuzzy neural network (FNN) was applied to predict the hydrogen concentration in the containment. The FNN model was developed and verified based on simulation data acquired by simulating MAAP4 code for optimized power reactor 1000. The FNN model is expected to assist operators to prevent a hydrogen explosion in severe accident situations and manage the accident properly because they are able to predict the changes in the trend of hydrogen concentration at the beginning of real accidents by using the developed FNN model.
Experimental and Theoretical Insights to Demonstrate the Hydrogen Evolution Activity of Layered Platinum Dichalcogenides Electrocatalysts
Mar 2021
Publication
Hydrogen is a highly efficient and clean renewable energy source and water splitting through electrocatalytic hydrogen evolution is a most promising approach for hydrogen generation. Layered transition metal dichalcogenides-based nano-structures have recently attracted significant interest as robust and durable catalysts for hydrogen evolution. We systematically investigated the platinum (Pt) based dichalcogenides (PtS2 PtSe2 and PtTe2) as highly energetic and robust hydrogen evolution electrocatalysts. PtTe2 catalyst unveiled the rapid hydrogen evolution process with the low overpotentials of 75 and 92 mV (vs. RHE) at a current density of 10 mA cm−2 and the small Tafel slopes of 64 and 59 mV/dec in acidic and alkaline medium respectively. The fabricated PtTe2 electrocatalyst explored a better catalytic activity than PtS2 and PtSe2. The density functional theory estimations explored that the observed small Gibbs free energy for H-adsorption of PtTe2 was given the prominent role to achieve the superior electrocatalytic and excellent stability activity towards hydrogen evolution due to a smaller bandgap and the metallic nature. We believe that this work will offer a key path to use Pt based dichalcogenides for hydrogen evolution electrocatalysts.
Effect of Hydrogen and Strain-Induced Martensite on Mechanical Properties of AISI 304 Stainless Steel
Jul 2016
Publication
Plastic deformation and strain-induced martensite (SIM α′) transformation in metastable austenitic AISI 304 stainless steel were investigated through room temperature tensile tests at strain rates ranging from 2 × 10−6 to 2 × 10−2/s. The amount of SIM was measured on the fractured tensile specimens using a feritscope and magnetic force microscope. Elongation to fracture tensile strength hardness and the amount of SIM increased with decreasing the strain rate. The strain-rate dependence of RT tensile properties was observed to be related to the amount of SIM. Specifically SIM formed during tensile tests was beneficial in increasing the elongation to fracture hardness and tensile strength. Hydrogen suppressed the SIM formation leading to hydrogen softening and localized brittle fracture.
Recent Progress in Hydrogen Flammability Prediction for the Safe Energy Systems
Nov 2020
Publication
Many countries consider hydrogen as a promising energy source to resolve the energy challenges over the global climate change. However the potential of hydrogen explosions remains a technical issue to embrace hydrogen as an alternate solution since the Hindenburg disaster occurred in 1937. To ascertain safe hydrogen energy systems including production storage and transportation securing the knowledge concerning hydrogen flammability is essential. In this paper we addressed a comprehensive review of the studies related to predicting hydrogen flammability by dividing them into three types: experimental numerical and analytical. While the earlier experimental studies had focused only on measuring limit concentration recent studies clarified the extinction mechanism of a hydrogen flame. In numerical studies the continued advances in computer performance enabled even multi-dimensional stretched flame analysis following one-dimensional planar flame analysis. The different extinction mechanisms depending on the Lewis number of each fuel type could be observed by these advanced simulations. Finally historical attempts to predict the limit concentration by analytical modelling of flammability characteristics were discussed. Developing an accurate model to predict the flammability limit of various hydrogen mixtures is our remaining issue.
Evaluation of Hydrogen Permeation Characteristics in Rubbery Polymers
Oct 2020
Publication
To find suitable sealing material with low permeability against hydrogen the elaborated evaluation techniques for hydrogen transport properties are necessary. We developed two techniques determining the permeability of hydrogen including software for diffusion behavior analysis. The techniques contain gas chromatography and volumetric collection of hydrogen gas. By measuring the hydrogen released from polymer samples with respect to the elapsed time after being decompressed from the high pressure total amount of adsorption and diffusivity (D) of hydrogen are evaluated with self-developed program of Fick's diffusion equation specified to a sample shape. The solubility (S) and permeability (P) of the polymers are determined through Henry's law and a relation of P=SD respectively. Developed techniques were applied to three kinds of spherical-shaped sealing rubbers NBR EPDM and FKM. The D S and P have been measured as function of pressure. The permeability obtained by both methods are discussed with Comsol simulation.
Development of Visible-Light-Driven Rh–TiO2-CeO2 Hybrid Photocatalysts for Hydrogen Production
Jul 2021
Publication
Visible-light-driven hydrogen production through photocatalysis has attracted enormous interest owing to its great potential to address energy and environmental issues. However photocatalysis possesses several limitations to overcome for practical applications such as low light absorption efficiency rapid charge recombination and poor stability of photocatalysts. Here the preparation of efficient noble metal–semiconductor hybrid photocatalysts for photocatalytic hydrogen production is presented. The prepared ternary Rh–TiO2–CeO2 hybrid photocatalysts exhibited excellent photocatalytic performance toward the hydrogen production reaction compared with their counterparts ascribed to the synergistic combination of Rh TiO2 and CeO2.
Risk Assessment Method Combining Independent Protection Layers (IPL) of Layer of Protection Analysis (LOPA) and RISKCURVES Software: Case Study of Hydrogen Refueling Stations in Urban Areas
Jul 2021
Publication
The commercialization of eco-friendly hydrogen vehicles has elicited attempts to expand hydrogen refueling stations in urban areas; however safety measures to reduce the risk of jet fires have not been established. The RISKCURVES software was used to evaluate the individual and societal risks of hydrogen refueling stations in urban areas and the F–N (Frequency–Number of fatalities) curve was used to compare whether the safety measures satisfied international standards. From the results of the analysis it was found that there is a risk of explosion in the expansion of hydrogen refueling stations in urban areas and safety measures should be considered. To lower the risk of hydrogen refueling stations this study applied the passive and active independent protection layers (IPLs) of LOPA (Layer of Protection Analysis) and confirmed that these measures significantly reduced societal risk as well as individual risk and met international standards. In particular such measures could effectively reduce the impact of jet fire in dispensers and tube trailers that had a high risk. Measures employing both IPL types were efficient in meeting international standard criteria; however passive IPLs were found to have a greater risk reduction effect than active IPLs. The combination of RISKCURVES and LOPA is an appropriate risk assessment method that can reduce work time and mitigate risks through protective measures compared to existing risk assessment methods. This method can be applied to risk assessment and risk mitigation not only for hydrogen facilities but also for hazardous materials with high fire or explosion risk.
Recent Advances in Carbon Dioxide Conversion: A Circular Bioeconomy Perspective
Jun 2021
Publication
Managing the concentration of atmospheric CO2 requires a multifaceted engineering strategy which remains a highly challenging task. Reducing atmospheric CO2 (CO2R) by converting it to value-added chemicals in a carbon neutral footprint manner must be the ultimate goal. The latest progress in CO2R through either abiotic (artificial catalysts) or biotic (natural enzymes) processes is reviewed herein. Abiotic CO2R can be conducted in the aqueous phase that usually leads to the formation of a mixture of CO formic acid and hydrogen. By contrast a wide spectrum of hydrocarbon species is often observed by abiotic CO2R in the gaseous phase. On the other hand biotic CO2R is often conducted in the aqueous phase and a wide spectrum of value-added chemicals are obtained. Key to the success of the abiotic process is understanding the surface chemistry of catalysts which significantly governs the reactivity and selectivity of CO2R. However in biotic CO2R operation conditions and reactor design are crucial to reaching a neutral carbon footprint. Future research needs to look toward neutral or even negative carbon footprint CO2R processes. Having a deep insight into the scientific and technological aspect of both abiotic and biotic CO2R would advance in designing efficient catalysts and microalgae farming systems. Integrating the abiotic and biotic CO2R such as microbial fuel cells further diversifies the spectrum of CO2R.
Hydrogen Production Possibility using Mongolian Renewable Energy
Jan 2019
Publication
There is widespread popular support for using renewable energy particularly solar and wind energy which provide electricity without giving rise to any carbon dioxide emissions. Harnessing these for electricity depends on the cost and efficiency of the technology which is constantly improving thus reducing costs per peak kilowatt and per kWh. Utilizing solar and wind-generated electricity in a stand-alone system requires corresponding battery or other storage capacity. The possibility of large-scale use of hydrogen in the future as a transport fuel increases the potential for both renewables and base-load electricity supply.
Electrical Double Layer Mechanism Analysis of PEM Water Electrolysis for Frequency Limitation of Pulsed Currents
Nov 2021
Publication
This paper proposes a method for improving hydrogen generation using pulse current in a proton exchange membrane-type electrolyzer (PEMEL). Traditional methods of electrolysis using direct current are known as the simplest approach to produce hydrogen. However it is highly dependent on environmental variables such as the temperature and catalyst used to enhance the rate of electrolysis. Therefore we propose electrolysis using a pulse current that can apply several dependent variables rather than environmental variables. The proposed method overcomes the difficulties in selecting the frequency of the pulse current by deriving factors affecting hydrogen generation while changing the concentration generated by the cell interface during the pulsed water-electrolysis process. The correlation between the electrolyzer load and the frequency characteristics was analyzed and the limit value of the applicable frequency of the pulse current was derived through electrical modeling. In addition the operating characteristics of PEMEL could be predicted and the PEMEL using the proposed pulse current was verified through experiments.
Evaluation Techniques of Hydrogen Permeation in Sealing Rubber Materials
Dec 2020
Publication
Three techniques for determining the hydrogen permeation properties of rubber samples were developed based on the volumetric and gravimetric measurements of released H2 gas after sample decompression. These methods include gas chromatography (GC) by thermal desorption analysis (TDA) volumetric collection (VC) measurement of hydrogen by graduated cylinder and gravimetric (GM) measurement by electronic balance. By measuring the released hydrogen against elapsed time after the decompression of pressure the charging amount (C0) and diffusivity (D) were obtained with the developed diffusion analysis program. From these values the solubility (S) and permeability (P) of polymers were evaluated through the relations of Henry's law and P=SD respectively. The developed techniques were applied to three kinds of spherically shaped sealing rubber materials. D S and P were analyzed as a function of pressure. The transport behaviors obtained in the three methods are discussed and compared with the characteristics of each measuring technique. The correlations between transport parameters and carbon black filler or density are discussed.
The Role of Hydrogen in Hydrogen Embrittlement of Metals: The Case of Stainless Steel
Apr 2019
Publication
Hydrogen embrittlement (HE) of metals has remained a mystery in materials science for more than a century. To try to clarify this mystery tensile tests were conducted at room temperature (RT) on a 316 stainless steel (SS) in air and hydrogen of 70 MPa. With an aim to directly observe the effect of hydrogen on ordering of 316 SS during deformation electron diffraction patterns and images were obtained from thin foils made by a focused ion beam from the fracture surfaces of the tensile specimens. To prove lattice contraction by ordering a 40% CW 316 SS specimen was thermally aged at 400 °C to incur ordering and its lattice contraction by ordering was determined using neutron diffraction by measuring its lattice parameters before and after aging. We demonstrate that atomic ordering is promoted by hydrogen leading to formation of short-range order and a high number of planar dislocations in the 316 SS and causing its anisotropic lattice contraction. Hence hydrogen embrittlement of metals is controlled by hydrogen-enhanced ordering during RT deformation in hydrogen. Hydrogen-enhanced ordering will cause the ordered metals to be more resistant to HE than the disordered ones which is evidenced by the previous observations where furnace-cooled metals with order are more resistant to HE than water-quenched or cold worked metals with disorder. This finding strongly supports our proposal that strain-induced martensite is a disordered phase.
A Study on the Characteristics of Academic Topics Related to Renewable Energy Using the Structural Topic Modelling and the Weak Signal Concept
Mar 2021
Publication
It is important to examine in detail how the distribution of academic research topics related to renewable energy is structured and which topics are likely to receive new attention in the future in order for scientists to contribute to the development of renewable energy. This study uses an advanced probabilistic topic modeling to statistically examine the temporal changes of renewable energy topics by using academic abstracts from 2010–2019 and explores the properties of the topics from the perspective of future signs such as weak signals. As a result in strong signals methods for optimally integrating renewable energy into the power grid are paid great attention. In weak signals interest in large-capacity energy storage systems such as hydrogen supercapacitors and compressed air energy storage showed a high rate of increase. In not-strong-but-well-known signals comprehensive topics have been included such as renewable energy potential barriers and policies. The approach of this study is applicable not only to renewable energy but also to other subjects.
Baking Effect on Desorption of Diffusible Hydrogen and Hydrogen Embrittlement on Hot-Stamped Boron Martensitic Steel
Jun 2019
Publication
Recently hot stamping technology has been increasingly used in automotive structural parts with ultrahigh strength to meet the standards of both high fuel efficiency and crashworthiness. However one issue of concern regarding these martensitic steels which are fabricated using a hot stamping procedure is that the steel is highly vulnerable to hydrogen delayed cracking caused by the diffusible hydrogen flow through the surface reaction of the coating in a furnace atmosphere. One way to make progress in understanding hydrogen delayed fractures is to elucidate an interaction for desorption with diffusible hydrogen behavior. The role of diffusible hydrogen on delayed fractures was studied for different baking times and temperatures in a range of automotive processes for hot-stamped martensitic steel with aluminum- and silicon-coated surfaces. It was clear that the release of diffusible hydrogen is effective at higher temperatures and longer times making the steel less susceptible to hydrogen delayed fractures. Using thermal desorption spectroscopy the phenomenon of the hydrogen delayed fracture was attributed to reversible hydrogen in microstructure sites with low trapping energy.
UV Assisted on Titanium Doped Electrode for Hydrogen Evolution from Artificial Wastewater
Jul 2018
Publication
Formaldehyde (H2CO) is the harmful chemical that used in variety of industries. However there are many difficulties to treat discharged H2CO in the wastewater. Hydrogen energy is arising as a one of the renewable energy that can replace fossil fuel. Many researches have been conducted on hydrogen production from electrolysis using expensive metal electrodes and catalysts such as platinum (Pt) and palladium (Pd). However they are expensive and have obstacles to directly use from the production. We used copper (Cu) as an electrode substrate because it has a good current density. To avoid corrosion issue of Cu substrate we used commercially available carbon (C) coated Cu substrate and synthesized titanium (Ti) on C/Cu substrate. We found that Ti was well synthesized and stayed on substrate after hydrogen evolution reaction (HER) in artificial wastewater. Moreover we quantified hydrogen production from the wastewater and compared it to pure water. Hydrogen production was enhanced in wastewater and H2CO was decomposed after reaction. We expected to use Ti-C/Cu electrode for hydrogen production of wastewater by electrolysis.
Numerical Analysis for Hydrogen Flame Acceleration during a Severe Accident in the APR1400 Containment Using a Multi-Dimensional Hydrogen Analysis System
Nov 2020
Publication
Korea Atomic Energy Research Institute (KAERI) established a multi-dimensional hydrogen analysis system to evaluate hydrogen release distribution and combustion in the containment of a Nuclear Power Plant (NPP) using MAAP GASFLOW and COM3D. In particular KAERI developed an analysis methodology for a hydrogen flame acceleration on the basis of the COM3D validation results against measured data of the hydrogen combustion tests in the ENACCEF and THAI facilities. The proposed analysis methodology accurately predicted the peak overpressure with an error range of approximately ±10% using the Kawanabe model used for a turbulent flame speed in the COM3D. KAERI performed a hydrogen flame acceleration analysis using the multi-dimensional hydrogen analysis system for a severe accident initiated by a station blackout (SBO) under the assumption of 100% metal–water reaction in the Reactor Pressure Vessel (RPV) to evaluate an overpressure buildup in the containment of the Advanced Power Reactor 1400 MWe (APR1400). The magnitude of the overpressure buildup in the APR1400 containment might be used as a criterion to judge whether the containment integrity is maintained or not when the hydrogen combustion occurs during a severe accident. The COM3D calculation results using the established analysis methodology showed that the calculated peak pressure in the containment was lower than the fracture pressure of the APR1400 containment. This calculation result might have resulted from a large air volume of the containment a reduced hydrogen concentration owing to passive auto-catalytic recombiners installed in the containment during the hydrogen release from the RPV and a lot of stem presence during the hydrogen combustion period in the containment. Therefore we found that the current design of the APR1400 containment maintained its integrity when the flame acceleration occurred during the severe accident initiated by the SBO accident.
High-Order Perturbation Solutions to a Lh2 Spreading Model With Continuous Spill
Sep 2011
Publication
High-order perturbation solutions have been obtained for the simple physical model describing the LH2 spreading with a continuous spill and are shown to improve over the first-order perturbation solutions. The non-dimensional governing equations for the model are derived to obtain more general solutions. Non-dimensional parameters are sought as the governing parameters for the non-dimensional equations and the non-dimensional evaporation rate is used as the perturbation parameter. The results show that the second-order solutions exhibit an improvement over the first-order solutions with respect to the pool volume; however there is still a difference between numerical solutions and second-order solutions in the late stage of spread. Finally it is revealed that the third-order solutions almost agree with numerical solutions.
Hydrogen Embrittlement Behavior of 18Ni 300 Maraging Steel Produced by Selective Laser Melting
Jul 2019
Publication
A study was performed to investigate the hydrogen embrittlement behavior of 18-Ni 300 maraging steel produced by selective laser melting and subjected to different heat treatment strategies. Hydrogen was pre-charged into the tensile samples by an electro-chemical method at the constant current density of 1 A m−2 and 50 A m−2 for 48 h at room temperature. Charged and uncharged specimens were subjected to tensile tests and the hydrogen concentration was eventually analysed using quadrupole mass spectroscopy. After tensile tests uncharged maraging samples showed fracture surfaces with dimples. Conversely in H-charged alloys quasi-cleavage mode fractures occurred. A lower concentration of trapped hydrogen atoms and higher elongation at fracture were measured in the H-charged samples that were subjected to solution treatment prior to hydrogen charging compared to the as-built counterparts. Isothermal aging treatment performed at 460 °C for 8 h before hydrogen charging increased the concentration of trapped hydrogen giving rise to higher hydrogen embrittlement susceptibility.
A Study on the Continuous Spill with Limited Period of Release
Sep 2013
Publication
In this study the spread of cryogenic liquid due to a limited period of release is investigated for the first time to clarify the unclear conventional concept regarding two release types continuous and instantaneous release. In describing instantaneous release a discharge time has been assumed to be infinitesimally small; however such an assumption is unreal because there exists a finite period of release no matter how rapid it is. If the discharge time is less than the entire time domain the instantaneous release model should be added to the continuous model from the end of the time. This combined release that consists of the initial continuous model and subsequent instantaneous model is more realistic than the instantaneous release. The physical phenomenon is governed by three parameters: the evaporation rate per unit area release time and spill quantity. Third-order perturbation solutions are obtained and compared with a numerical solution to verify the perturbation solution. For the same spill quantity the combined model that consists of continuous and subsequent instantaneous model is necessary for small release times whereas the continuous model is only required for large release times. Additionally the combined release model is necessary for a small spill quantity at a fixed release time. These two release models are clearly distinguished using the perturbation solution.
Hydrogen Production by Electrochemical Reaction Using Ethylene Glycol with Terephthalic Acid
Jan 2021
Publication
In this study ethylene glycol (EG) and terephthalic acid (TPA) were used to generate hydrogen using copper electrodes in an alkaline aqueous solution and the corresponding reaction mechanism was experimentally investigated. Both EG and TPA produced hydrogen; however TPA consumed OH− inhibiting the production of intermediary compounds of EG and causing EG to actively react with H2O ultimately leading to enhanced hydrogen production. In addition the initiation potential of water decomposition of the EG and TPA alkaline aqueous solution was 1.0 V; when 1.8 V (vs. RHE) was applied the hydrogen production reached 440 mmol L−1 which was substantially greater than the hydrogen production rate of 150 mmol L−1 during water decomposition.
Experimental Study on a Hydrogen Stratification Induced by PARs Installed in a Containment
Oct 2020
Publication
Hydrogen can be produced in undesired ways such as a high temperature metal oxidation during an accident. In this case the hydrogen must be carefully managed. A hydrogen mitigation system (HMS) should be installed to protect a containment of a nuclear power plant (NPP) from hazards of hydrogen produced by an oxidation of the fuel cladding during a severe accident in an NPP. Among hydrogen removal devices passive auto-catalytic recombiners (PARs) are currently applied to many NPPs because of passive characteristics such as not requiring a power supply nor an operators’ manipulations. However they offer several disadvantages resulting in issues related to hydrogen control by PARs. One of the issues is a hydrogen stratification in which hydrogen is not well-mixed in a compartment due to the high temperature exhaust gas of PARs and accumulation in the lower part. Therefore experimental simulation on hydrogen stratification phenomenon by PARs is required. When the hydrogen stratification by PARs is observed in the experiment the verification and improvement of a PAR analysis model using the experimental results can be performed and the hydrogen removal characteristics by PARs installed in an NPP can be evaluated using the improved PAR model. View Full-Text
Development of NaBH4-Based Hydrogen Generator for Fuel Cell Unmanned Aerial Vehicles with Movable Fuel Cartridge
Mar 2019
Publication
NaBH4-based hydrogen generator for fuel cell Unmanned Aerial Vehicle (UAVs) with movable fuel cartridge was developed in the present study. The main fuel of hydrogen generator is Sodium borohydride (NaBH4) that is a kind of chemical hydride and has a high hydrogen storage density. In the previous studies hydrogen generators were developed in which hydrogen was directly generated from solid state NaBH4. However it was a prototype so inconvenient to replace the fuel after used up and lacked user convenience. Therefore the performance evaluation and the development procedure of NaBH4-based hydrogen generator that was designed taking user convenience in consideration for commercialization were described in this paper.
Comparison of Solutions for a Liquid Pool Spreading Model with Continuous and Instantaneous Spills
Sep 2013
Publication
In this study a solution for a liquid pool spreading model with a continuous spill is compared with that for a liquid pool spreading model with an instantaneous spill under the same total release volume. As reducing spill time in completely releasing liquid from a tank it is evaluated whether the solution for a continuous spill approaches to that for an instantaneous spill or not. Also effects of the viscous term in the liquid pool spreading model with continuous and instantaneous spills on the liquid pool spreading behaviour are investigated.
Continuous Hydrogen Regeneration Through the Oxygen Vacancy Control of Metal Oxides Using Microwave Irradiation
Nov 2018
Publication
The amount of hydrogen gas generated from metal oxide materials based on a thermochemical water-splitting method gradually reduces as the surface of the metal oxide oxidizes during the hydrogen generation process. To regenerate hydrogen the oxygen reduction process of a metal oxide at high temperatures (1000–2500 °C) is generally required. In this study to overcome the problem of an energy efficiency imbalance in which the required energy of the oxygen reduction process for hydrogen regeneration is higher than the generated hydrogen energy we investigated the possibility of the oxygen reduction of a metal oxide with a low energy using microwave irradiation. For this purpose a macroporous nickel-oxide structure was used as a metal oxide catalyst to generate hydrogen gas and the oxidized surface of the macroporous nickel-oxide structure could be reduced by microwave irradiation. Through this oxidation reduction process ∼750 μmol g−1 of hydrogen gas could be continuously regenerated. In this way it is expected that oxygen-enriched metal oxide materials can be efficiently reduced by microwave irradiation with a low power consumption of <∼4% compared to conventional high-temperature heat treatment and thus can be used for efficient hydrogen generation and regeneration processes in the future.
Hydrogen Fueling Standardization: Enabling ZEVs with "Same as Today" Fueling and FCEV Range and Safety
Oct 2015
Publication
Zero Emission Vehicles (ZEVs) are necessary to help reduce the emissions in the transportation sector which is responsible for 40% of overall greenhouse gas emissions. There are two types of ZEVs Battery Electric Vehicles (BEVs) and Fuel Cell Electric Vehicles (FCEVs) Commercial Success of BEVs has been challenging thus far also due to limited range and very long charging duration. FCEVs using H2 infrastructure with SAE J2601 and J2799 standards can be consistently fuelled in a safe manner fast and resulting in a range similar to conventional vehicles. Specifically fuelling with SAE J2601 with the SAE J2799 enables FCEVs to fill with hydrogen in 3-5 minutes and to achieve a high State of Charge (SOC) resulting in 300+ mile range without exceeding the safety storage limits. Standardized H2 therefore gives an advantage to the customer over electric charging. SAE created this H2 fuelling protocol based on modelling laboratory and field tests. These SAE standards enable the first generation of commercial FCEVs and H2 stations to achieve a customer acceptable fueling similar to today's experience. This report details the advantages of hydrogen and the validation of H2 fuelling for the SAE standards.
The Analysis of Fire Test for the High Pressure Composite Cylinder
Sep 2011
Publication
A large number of natural gas vehicles (NGV) with composite cylinders run in the world. In order to store hydrogen using the composite cylinder has also reached commercialization for the hydrogen fuel cell vehicle (FCV) which is been developing on ECO Energy. Under these increasing circumstances the most important issue is that makes sure of safety of the hydrogen composite cylinder. In case of the composite cylinder a standards to verify the safety of cylinders obey several country's standards. For NGV ISO 11439 has adopted as international standards but for FCV it has been still developing and there is only ISO/TS 15869 as international technical standards. In contents of international standards the fire test is the weakest part. The fire test is that the pressure relief valves (PRD) normally operate or not in order to prevent cylinders bursting when a vehicle is covered by fire. However with present standards there is no method to check the problem from vehicles in local flame. This study includes fire test results that have been performed to establish the fire-test standards.
Assessment of Safety for Hydrogen Fuel Cell Vehicle
Sep 2011
Publication
A prospective global market share of Electric vehicle (EV) Hybrid electric vehicle (HEV) and Hydrogen Fuel Cell Vehicle (HFCV) is expected to grow due to stringent emission regulation and oil depletion. However it is essential to secure protection against high-pressure hydrogen gas and high-voltage in fuel cell vehicles and thus needs to develop a technique for safety assessment of HFCV. In this experiment 8 research institutes including the Korea Automobile Testing and Research Institute Hyundai Motor Company took part in. This project was supported by the Ministry of Land Transportation and Maritime Affairs of the Republic of Korea.
Numerical Investigation of the Initial Charging Process of the Liquid Hydrogen Tank for Vehicles
Dec 2022
Publication
Liquid hydrogen has been studied for use in vehicles. However during the charging process liquid hydrogen is lost as gas. Therefore it is necessary to estimate and reduce this loss and simulate the charging process. In this study the initial charging process of a vehicle liquid hydrogen tank under room temperature and atmospheric pressure conditions was numerically investigated. A transient thermal-fluid simulation with a phase-change model was performed to analyze variations in the volume pressure mass flow rate and temperature. The results showed that the process could be divided into three stages. In the first stage liquid hydrogen was actively vaporized at the inner wall surface of the storage tank. The pressure increased rapidly and liquid droplets were discharged into the vent pipe during the second stage. In the third stage the mass flow rates of liquid and hydrogen gas at the outlet showed significant fluctuations owing to complex momentum generated by the evaporation and charging flow. The temperatures of the inner and outer walls and insulation layer decreased significantly slower than that of the gas region because of its high heat capacity and insulation effect. The optimal structure should be further studied because the vortex stagnation and non-uniform cooling of the wall occurred near the inlet and outlet pipes.
The Study on the Internal Temperature Change of Type 3 and Type 4 Composite Cylinder During Filling
Sep 2013
Publication
The number of eco friendly vehicle which is using green energy such as natural gas(NG) and hydrogen(H2) is rapidly increasing in the world. Almost all of the car manufacturers are adopting the pressurizing fuel method to storage gas. The fuel storage system which can pressurize the fuel as high as possible is necessary to maximize the mileage of the vehicle. In Korea the most important issue is that makes sure of safety of the fuel storage system and several tests are performed to verify safety of the composite cylinder especially for Type 3 and Type 4. In this research an empirical study on the internal temperature change of Type 3 and Type 4 composite cylinder during filling is performed by gas cycling test equipment. In order to measure the temperature totally twelve sensors(every four sensors on the top middle and bottom) are installed in each cylinder. As a consequence large amount of compression heat is generated during rapid filling and the result temperature change in Type 4 is greater than Type 3 is confirmed depending on property of the liner material such as thermal conduction and thickness of carbon composite.
Numerical Analysis of the Effects of Ship Motion on Hydrogen Release and Dispersion in an Enclosed Area
Jan 2022
Publication
Hydrogen is an alternative to conventional heavy marine fuel oil following the initial strategy of the International Maritime Organization (IMO) for reducing greenhouse gas emissions. Although hydrogen energy has many advantages (zero-emission high efficiency and low noise) it has considerable fire and explosion risks due to its thermal and chemical characteristics (wide flammable concentration range and low ignition energy). Thus safety is a key concern related to the use of hydrogen. Whereas most previous studies focused on the terrestrial environment we aim to analyze the effects of the ship’s motion on hydrogen dispersion (using commercial FLUENT code) in an enclosed area. When compared to the steady state our results revealed that hydrogen reached specific sensors in 63% and 52% less time depending on vessel motion type and direction. Since ships carry and use a large amount of hydrogen as a power source the risk of hydrogen leakage from collision or damage necessitates studying the correspondence between leakage diffusion and motion characteristics of the ship to position the sensor correctly.
Synthesis of Spherical V-Nb-Mo-Ta-W High-Entropy Alloy Powder Using Hydrogen Embrittlement and Spheroidization by Thermal Plasma
Dec 2019
Publication
V-Nb-Mo-Ta-W high-entropy alloy (HEA) one of the refractory HEAs is considered as a next-generation structural material for ultra-high temperature uses. Refractory HEAs have low castability and machinability due to their high melting temperature and low thermal conductivity. Thus powder metallurgy becomes a promising method for fabricating components with refractory HEAs. Therefore in this study we fabricated spherical V-Nb-Mo-Ta-W HEA powder using hydrogen embrittlement and spheroidization by thermal plasma. The HEA ingot was prepared by vacuum arc melting and revealed to have a single body-centered cubic phase. Hydrogen embrittlement which could be achieved by annealing in a hydrogen atmosphere was introduced to get the ingot pulverized easily to a fine powder having an angular shape. Then the powder was annealed in a vacuum atmosphere to eliminate the hydrogen from the hydrogenated HEA resulting in a decrease in the hydrogen concentration from 0.1033 wt% to 0.0003 wt%. The angular shape of the HEA powder was turned into a spherical one by inductively-coupled thermal plasma allowing to fabricate spherical V-Nb-Mo-Ta-W HEA powder with a d50 value of 28.0 μm.
Study on the Explosion of the Hydrogen Fuel Tank of Fuel Cell Electric Vehicles in Semi-Enclosed Spaces
Dec 2022
Publication
The rise in hydrogen fuel cell electric vehicles (FCEVs) is expected to pose a variety of hazards on the road. Vehicles using hydrogen could cause significant damage owing to hydrogen vapor cloud explosions jet fires caused by leakage or hydrogen tank explosions. This risk is expected to further increase in semi-enclosed spaces such as underground parking lots and road tunnels. Therefore it is necessary to study the fire safety of hydrogen vehicles in semi-enclosed spaces. In this study an experiment on hydrogen tank explosion was performed. In addition the CFD numerical model was verified using the experimental results and the damaging effect due to pressure propagation during hydrogen tank explosions in underground parking lots and road tunnels was analyzed using numerical analysis. From the experiment results the hydrogen tank exploded at about 80 Mpa a maximum incident pressure is generated 267 kPa at a distance of 1.9 m. As a result of numerical analysis based on the experimental results the limit distance that can cause serious injury due to the explosion of a hydrogen tank in a road tunnel or underground parking lot was analyzed up to about 20 m from the point of explosion.
Explosion Characteristics of Hydrogen Gas in Varying Ship Ventilation Tunnel Geometries: An Experimental Study
Apr 2022
Publication
Hydrogen is widely regarded as a key element of prospective energy solutions for alleviating environmental emission problems. However hydrogen is classified as a high-risk gas because of its wide explosive range high overpressure low ignition energy and fast flame propagation speed compared with those of hydrocarbon-based gases. In addition deflagration can develop into detonation in ventilation or explosion guide tunnels if explosion overpressure occurs leading to the explosion of all combustible gases. However quantitative evidence of an increase in the explosion overpressure of ventilation tunnels is unavailable because the explosive characteristics of hydrogen gas are insufficiently understood. Therefore this study investigated an explosion chamber with the shape of a ventilation pipe in a ship compartment. The effect of tunnel length on explosion overpressure was examined experimentally. For quantitative verification the size of the hydrogen gas explosion overpressure was analyzed and compared with experimental values of hydrocarbon-based combustible gases (butane and LPG (propane 98%)). The experimental database can be used for explosion risk analyses of ships when designing ventilation holes and piping systems and developing new safety guidelines for hydrogen carriers and hydrogen-fueled ships.
A Comparative Feasibility Study of the Use of Hydrogen Produced from Surplus Wind Power for a Gas Turbine Combined Cycle Power Plant
Dec 2021
Publication
Because of the increasing challenges raised by climate change power generation from renewable energy sources is steadily increasing to reduce greenhouse gas emissions especially CO2 . However this has escalated concerns about the instability of the power grid and surplus power generated because of the intermittent power output of renewable energy. To resolve these issues this study investigates two technical options that integrate a power-to-gas (PtG) process using surplus wind power and the gas turbine combined cycle (GTCC). In the first option hydrogen produced using a power-to-hydrogen (PtH) process is directly used as fuel for the GTCC. In the second hydrogen from the PtH process is converted into synthetic natural gas by capturing carbon dioxide from the GTCC exhaust which is used as fuel for the GTCC. An annual operational analysis of a 420-MWclass GTCC was conducted which shows that the CO2 emissions of the GTCC-PtH and GTCC-PtM plants could be reduced by 95.5% and 89.7% respectively in comparison to a conventional GTCC plant. An economic analysis was performed to evaluate the economic feasibility of the two plants using the projected cost data for the year 2030 which showed that the GTCC-PtH would be a more viable option.
Temperature Change of a Type IV Cylinder During Hydrogen Fuelling Process
Sep 2009
Publication
The temperature of the hydrogen cylinder needs to be carefully controlled during fuelling process. The maximum temperature should be less than 85℃ according to the ISO draft code. If the fuelling period is reduced the maximum temperature should increase. In this study temperature change of a Type IV cylinder was measured during the hydrogen fuelling process up to 35 MPa. Fuelling period was 3 to 5 minutes. Twelve thermocouples were installed to measure inside gas temperature and seven were attached on the outside of the cylinder. An infrared camera was also used for measuring temperature distribution of outside of cylinder. The maximum gas temperature was higher than 85℃ inside of the cylinder. Significant temperature difference between the upper and lower part of the vessel was observed. Temperature near the plug and the valve was quickly increased and maintained higher than that of the other region. Temperature increases for the partial refuelling process were also discussed.
Strategy for Selecting an Optimal Propulsion System of a Liquefied Hydrogen Tanker
Jan 2017
Publication
This study proposed a strategy for selecting an optimal propulsion system of a liquefied hydrogen tanker. Four propulsion system options were conceivable depending on whether the hydrogen BOG (boil-off gas) from the cryogenic cargo tanks was used for fuel or not. These options were evaluated in terms of their economic technological and environmental feasibilities. The comparison scope included not only main machinery but also the BOG handling system with electric generators. Cost-benefit analysis life-cycle costing including carbon tax and an energy efficiency design index were used as measures to compare the four alternative systems. The analytic hierarchy process made scientific decision-making possible. This methodology provided the priority of each attribute through the use of pairwise comparison matrices. Consequently the propulsion system using LNG with hydrogen BOG recovery was determined to be the optimal alternative. This system was appropriate for the tanker that achieved the highest evaluation score.
Recent Progress Using Solid-State Materials for Hydrogen Storage: A Short Review
Feb 2022
Publication
With the rapid growth in demand for effective and renewable energy the hydrogen era has begun. To meet commercial requirements efficient hydrogen storage techniques are required. So far four techniques have been suggested for hydrogen storage: compressed storage hydrogen liquefaction chemical absorption and physical adsorption. Currently high-pressure compressed tanks are used in the industry; however certain limitations such as high costs safety concerns undesirable amounts of occupied space and low storage capacities are still challenges. Physical hydrogen adsorption is one of the most promising techniques; it uses porous adsorbents which have material benefits such as low costs high storage densities and fast charging–discharging kinetics. During adsorption on material surfaces hydrogen molecules weakly adsorb at the surface of adsorbents via long-range dispersion forces. The largest challenge in the hydrogen era is the development of progressive materials for efficient hydrogen storage. In designing efficient adsorbents understanding interfacial interactions between hydrogen molecules and porous material surfaces is important. In this review we briefly summarize a hydrogen storage technique based on US DOE classifications and examine hydrogen storage targets for feasible commercialization. We also address recent trends in the development of hydrogen storage materials. Lastly we propose spillover mechanisms for efficient hydrogen storage using solid-state adsorbents.
Layered Transition Metal Selenophosphites for Visible Light Photoelectrochemical Production of Hydrogen
Jun 2021
Publication
The growing consumption of global energy has posed serious challenges to environmental protection and energy supplies. A promising solution is via introducing clean and sustainable energy sources including photoelectrochemical hydrogen fuel production. 2D materials such as transition metal trichalcogenphosphites (MPCh3) are gaining more and more interest for their potential as photocatalysts. Crystals of transition metal selenophosphites namely MnPSe3 FePSe3 and ZnPSe3 were tested as photocatalysts for the hydrogen evolution reaction (HER). ZnPSe3 is the one that exhibited the lowest overpotential and the higher response to the light during photocurrent experiments in acidic media. For this reason among the crystals in this work it is the most promising for the photocatalyzed production of hydrogen.
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