Considerable Amount Of Hydrogen Research Articles

Risk-averse electrolyser sizing in industrial parks: An efficient stochastic-robust approach

Hydrogen is called to be one of the most important energy vectors in future energy systems. Nowadays, its use in the industry sector is prominent, finding multiple applications in fertilizer production or oil refining. In this sense, some industry sectors demand a considerable amount of hydrogen for their processes. In many cases, hydrogen must be purchased externally, which supposes a challenge due to hydrogen transportation is costly and few efficient. In this context, local hydrogen production through mature electrolysis technology may suppose an attractive alternative in industrial parks. This paper focuses on this topic, in particular, a risk-averse electrolyser sizing methodology is developed. The new approach accounts for uncertainties in electricity prices as well as local renewable generation and demand through an original hybrid stochastic-robust model. The developed uncertainty modelling is integrated into a novel four-level optimization framework, whose main result is the optimal electrolyser rated power. To efficiently attain the solution, an original hybridization of the Benders' decomposition and the Column and Constraint Generation Algorithm is proposed. The developed methodology results efficient in an illustrative three-industry park, showing that installing local hydrogen generation may reduce the amount of hydrogen purchased externally (by 38%) and project costs by 2.5%. Furthermore, increasing the robustness level leads to increase the project cost by 8%, while assuming unfavourable realization of uncertainties. Moreover, the developed tool is further validated in larger parks, involving an increasing number of industries, showing that the proposed methodology scales well with the size of the park.

Visualization of Hydrogen Bubbles Using Synchrotron X-Ray CT inside Porous Transport Layer of Direct Toluene Electro-Hydrogenation Electrolyzers

Toluene is a highly versatile solvent commonly used in many industries due to its high energy density and effective hydrogen carrier properties. It can store a considerable amount of hydrogen in a relatively small volume, making it a promising hydrogen carrier for various applications. Toluene's high volumetric energy density also makes it one of the best hydrogen carriers available. Additionally, toluene is easy to handle and transport as it is a liquid at room temperature, and it can be stored and transported like any other liquid fuel. Furthermore, toluene is a safer alternative for hydrogen storage compared to other hydrocarbons due to its low toxicity.Direct toluene-electro hydrogenation electrolyzer is a promising method that enables the simultaneous performance of water electrolysis and toluene hydrogenation in a single system. However, during the toluene direct electrolytic hydrogenation process, the formation of hydrogen bubbles from the electrolysis of water hinders the toluene hydrogenation reaction, leading to a reduced conversion rate of methylcyclohexane (MCH) and Faraday efficiency.In this study, we aimed to understand the conditions for hydrogen bubble generation and transport. We quantitatively evaluated the generation amount and distribution of hydrogen bubbles by visualizing them in an operating electrochemical cell using Synchrotron X-ray CT. Figure 1 displays the distribution of hydrogen bubbles along the porous transport layer (PTL) of the electrochemical cell. These bubbles were visualized using the raw images obtained from Spring-8 and subsequently reconstructed. The cell was operating at a current density of 200 mA/cm2 for a period of 30 minutes with pure water supplied to the anode side. Darker areas in the images indicate regions with hydrogen bubbles, which have a lower density and atomic weight than other substances in the PTL. Therefore, they are more transparent to X-rays and appear darker in the image. Higher current values and longer operation times led to increased hydrogen bubble generation, with a significant increase observed at 30 minutes. By visualizing these hydrogen bubbles, we were able to evaluate the generation distribution, amount, and transport of hydrogen, which can help improve the direct toluene-electro hydrogenation electrolyzer system. Acknowledgement This study was based on results obtained from the Development of Fundamental Technology for Advancement of Water Electrolysis Hydrogen Production in Advancement of Hydrogen Technologies and Utilization Project (P14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References Nagasawa K, Sugita Y, Atienza-Márquez A, Kuroda Y, Mitsushima S. Effect of the cathode catalyst loading on mass transfer in toluene direct electrohydrogenation. Journal of Electroanalytical Chemistry 2023:117431. https://doi.org/10.1016/J.JELECHEM.2023.117431.Shigemasa, A. Atienza-Márquez, K. Inoue, S. Jang, F. Reyna-Peña, T. Araki, “Visualization of dragged water and generated hydrogen bubbles in a direct toluene electro-hydrogenation electrolyzer,” J. Power Sources 2023; 554:232304. https://doi.org/10.1016/j.jpowsour.2022.232304.Nagasawa, A. Kato, Y. Nishiki, Y. Matsumura, M. Atobe, S. Mitsushima, “The effect of flow-field structure in toluene hydrogenation electrolyzer for energy carrier synthesis system. Electrochemical Acta 2017; 246:459-65. https://doi.org/10.1016/j.electacta.2017.06.081. Nagasawa, K. Tanimoto, J. Koike, K. Ikegami, S. Mitushima, “Toluene permeation through solid polymer electrolyte during toluene direct electro-hydrogenation for energy carrier synthesis”, Journal of Power Sources, Vol.439, (2019) 22707. https://doi.org/10.1016/j.jpowsour.2019.227070. Figure 1 SPring-8 CT Visualization Reconstructed image after 30 minutes of operation at 200 mA/cm². Figure 1

Thermodynamic and exergoeconomic analysis of a multi-generation gas-to-X system based on fuel-rich combustion to produce power, hydrogen, steam and heat

Besides paying more attention to renewables, developing efficient multi-generation systems fed by currently available energy sources is another pathway to sustainable development. Meanwhile, hydrogen production will play a key role in the green transition. The present work investigates a multi-generation gas-to-X system to produce power, hydrogen, steam, and heat from thermodynamic and economic points of view. The proposed system includes a gas turbine, a water gas shift reactor, membrane, inverted Brayton cycle and recuperated organic Rankine cycles. The partial oxidation of the rich mixture in the combustion chamber of the gas turbine results in the presence of a considerable amount of hydrogen in the combustion products, through which, in addition to generating power and heat, there can also be hydrogen production. Results showed that the cost of produced hydrogen ranges from 8.13 to 2.12 $/kg and the overall exergy efficiency ranges from 54 to 62% for equilibrium ratios of 1.65–2.9. Besides, the cost of power generated by the gas turbine and the total cost rate of the system at an equilibrium ratio of 2 is obtained to be 47.7 $/MWh and 248 $/h, respectively.

Reversible storage and release of hydrogen with LOHC: Evaluation of thermochemical data for methyl-quinolines with complementary experimental and computational methods

The liquid organic hydrogen carriers (LOHC) are aromatic molecules, which can be considered as an attractive option for the storage and transport of hydrogen. A considerable amount of hydrogen can be loaded and unloaded with a reversible chemical reaction. Methyl-substituted quinolines are available from petroleum, coal processing, wood preservation or they can be synthesized from aniline. Quinolines can be considered as potential LOHC systems, provided they have favorable thermodynamic properties, which were the focus of this current study. The absolute vapor pressures of methyl-quinolines were measured using the transpiration method. The standard molar enthalpies of vaporization of methyl-quinolines were derived from the vapor pressure temperature dependences. Thermodynamic data on vaporization and formation enthalpies available in the literature were collected, evaluated, and combined with own experimental results. The theoretical standard molar gas-phase enthalpies of formation of methyl-quinolines, calculated using the quantum chemical G3MP2 and G4 methods, agreed well with the evaluated experimental data. The hydrogenation/dehydrogenation reaction enthalpies of methyl-quinolines were calculated and compared with the data for other potential liquid organic hydrogen carriers. The comparatively low enthalpies of reaction make these heteroaromatics a seminal LOHC systems.

Hydrogen Storage: Thermodynamic Analysis of Alkyl-Quinolines and Alkyl-Pyridines as Potential Liquid Organic Hydrogen Carriers (LOHC)

The liquid organic hydrogen carriers (LOHC) are aromatic molecules, which can be considered as an attractive option for the storage and transport of hydrogen. A considerable amount of hydrogen up to 7–8% wt. can be loaded and unloaded with a reversible chemical reaction. Substituted quinolines and pyridines are available from petroleum, coal processing, and wood preservation, or they can be synthesized from aniline. Quinolines and pyridines can be considered as potential LOHC systems, provided they have favorable thermodynamic properties, which were the focus of this current study. The absolute vapor pressures of methyl-quinolines were measured using the transpiration method. The standard molar enthalpies of vaporization of alkyl-substituted quinolines and pyridines were derived from the vapor pressure temperature dependencies. Thermodynamic data on vaporization and formation enthalpies available in the literature were collected, evaluated, and combined with our own experimental results. The theoretical standard molar gas-phase enthalpies of formation of quinolines and pyridines, calculated using the quantum-chemical G4 methods, agreed well with the evaluated experimental data. Reliable standard molar enthalpies of formation in the liquid phase were derived by combining high-level quantum chemistry values of gas-phase enthalpies of formation with experimentally determined enthalpies of vaporization. The liquid-phase hydrogenation/dehydrogenation reaction enthalpies of alkyl-substituted pyridines and quinolines were calculated and compared with the data for other potential liquid organic hydrogen carriers. The comparatively low enthalpies of reaction make these heteroaromatics a seminal LOHC system.

A comparative fracture analysis on as-received and electrochemically hydrogen charged API X60 and API X60SS pipeline steels subjected to tensile testing

In this study, a comparative analysis of fracture surfaces in API X60 and API X60SS pipeline steels is carried out after hydrogen charging followed by tensile testing. The JIS test setup is also utilized in order to measure the amount of discharged hydrogen through the microstructure of both steels. EBSD measurements are also done on as-received and hydrogen charged specimens in order to observed the HIC propagation. The results show that a considerable amount of hydrogen is able to diffuse through the microstructure of both steels. The tensile testing after hydrogen charging proves that hydrogen embrittlement occurs significantly in both steels. At the center of cross section in both steels, the fracture occurs by micro-voids formation, their growth and coalescence around the different types of inclusions. In charged specimens, dimples are shallower in both specimens compared with the dimples in the fracture surfaces of as-received specimens. Comparatively, hydrogen embrittlement in API X60 steel is more noticeable and its surface is more flat than the API X60SS steel. In hydrogen-charged API X60 steel, EBSD map shows a crack stepwise jumping with 45° from one crack traction line to another, with both intergranular and transgranular crack propagation mechanisms. Moreover, the crack propagates intergranularly along gains with mismatch Taylor values, while transgranular propagation mostly observed within the hard grains with high amount of dislocation density and internal energy associated with KAM map. In the case of API X60SS steel, no evidence of HIC crack was observed.

Application of helium-neon red laser for increasing biohydrogen production from anaerobic digestion of biowastes

Biohydrogen has significant feasibility since biological processes are much less energy intensive compared with electrolysis and thermo-chemical processes. It is widely recognized that considerable amounts of hydrogen (H2) can be produced from renewable resources without using energy from fossil fuels. Biological processes and bacterial fermentation are considered as the most environmentally friendly alternatives for satisfying future hydrogen demand. Biohydrogen production from agricultural and agro-industrial solid waste and wastewater is considered as highly advantageous as materials of this kind are abundant, cheap and biodegradable. The combustion of H2 with oxygen produces water as its only product: Unlike other fuels, the combustion of H2 does not produce carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), hydrocarbons or particulate matter (PM). Therefore, hydrogen is an environmentally friendly fuel where endeavors focus on producing specially designed internal combustion engines that can use H2 as fuel. The results showed that laser irradiated inoculum increased biohydrogen production by 1.2 times of the control. Therefore, in this research, it was hypothesized that exposing purple non-sulfur bacterial (PNSB) mix consortium to Helium-Neon red laser for 2 hours increased cell activity and consequently the biohydrogen production from food wastes through photo-fermentation process.

Biological methanation of injected hydrogen in a two-stage anaerobic digestion process

In the field of biological hydrogen methanation, ideal process parameters are underexplored for continuous two-stage systems with anaerobic filters.The present study aims at filling this gap for continuous in-situ reactors while applying different hydrogen injection rates. The results of the study demonstrate an almost complete acid degradation on the output side of the anaerobic filter fed by hydrolysate from maize silage and silage effluent. Most of the oxidizable substances were transferred to methane, but hydrogen could not be completely converted. With fully stoichiometric hydrogen addition, a methane production rate of 0.88 ± 0.06 m3d−1 per m3 reactor volume was reached. With half stoichiometric hydrogen addition, a hydrogen conversion rate of 75.53 ± 3.77% was obtained.The present approach proved to be a promising contribution to power-to-gas technology, as a considerable amount of hydrogen had to be converted into methane while carbon dioxide was fixed.

Yüksek Miktarlarda Şeker Pancarı Melasının Hidrojen ve 5-Aminolevulinik Asit Üretimi için Substrat Olarak Değerlendirilmesi

Sugar beet molasses is a valuable raw material and it contains high amount of sugar especially sucrose. Therefore, it could be used as substrate for the generation of highly valuable chemicals by microorganisms. Here, considerably high concentrations of molasses were tested for the first time to investigate if they could enhance the growth of Rhodobacter sphaeroides O.U.001 and generations of hydrogen and 5-aminolevulinic acid (5-ALA). Firstly, five distinct growth cultures having sugar contents of 34 g/L, 41 g/L, 48 g/L, 55 g/L and 61 g/L were made ready using molasses. Then, in batch processes, bacterial growth and generations of hydrogen and 5-ALA were investigated in these media. As a result, the highest cell growth (OD660: 9.26, 4.54 g cdw/L) to date was achieved in 34 g/L sugar containing medium. Similarly, the highest quantity of 5-ALA (37.44 mM) to date was attained in the same growth culture. In addition to these significant improvements, at maximum 21.02 mL (0.42 L H2/L) of hydrogen was collected from 34 g/L sugar containing medium. To conclude, using a sugar concentration of 34 g/L yielded the highest bacterial growth and 5-ALA generation so far. And, it also supported the generation of considerable amount of hydrogen.

Flash Graphene from Plastic Waste.

In this work, an approach to upcycling plastic waste (PW) products is presented. The method relies on flash Joule heating (FJH) to convert PW into flash graphene (FG). In addition to FG, the process results in the formation of carbon oligomers, hydrogen, and light hydrocarbons. In order to make high-quality graphene, a sequential alternating current (AC) and direct current (DC) flash is used. The FJH process requires no catalyst and works for PW mixtures, which makes the process suitable for handling landfill PW. The energy required to convert PW to FG is ∼23 kJ/g or ∼$125 in electricity per ton of PW, potentially making this process economically attractive for scale-up. The FG was characterized by Raman spectroscopy and had an I2D/IG peak ratio up to 6 with a low-intensity D band. Moreover, transmission electron microscopy and X-ray diffraction analysis show that the FG is turbostratic with an interlayer spacing of 3.45 Å. The large interlayer spacing will facilitate its dispersion in liquids and composites. Analysis of FG dispersions in 1% Pluronic aqueous solution shows that concentrations up to 1.2 mg/mL can be achieved. The carbon oligomers that distilled from the process were characterized by Fourier transform infrared spectroscopy and have chemical structures similar to the starting PW. Initial analysis of gas-phase products shows the formation of considerable amounts of hydrogen along with other light hydrocarbons. As graphene is naturally occurring and shows a low toxicity profile, this could be an environmentally beneficial method to upcycle PW.

The crystal structure of ZrCr2D≈4 at 50 K ≤ T ≤ 200 K

Abstract Many Laves phases take up considerable amounts of hydrogen to form metallic Laves phase hydrides. They frequently undergo phase transitions driven by ordering phenomena for the hydrogen atom distribution. The cubic Laves phase ZrCr2 takes up hydrogen to form a hydride with almost four hydrogen atoms per formula unit, which undergoes a phase transition to a monoclinic modification at a critical temperature T c = 250.2 K. Its crystal structure was refined based on neutron powder diffraction data on the deuteride (ZrCr2D3.8 type [T = 1.6 K, C2/c]) at four temperatures in the range 50 K ≤ T ≤ 200 K. The monoclinic low-temperature modification features a strongly distorted square anti-prism ZrD8 and three CrD4 polyhedra with almost fully occupied deuterium sites in saddle-like, distorted tetrahedral and planar configurations. Zr–D distances are in the range 201.4(7) pm ≤ d(Zr–D) ≤ 208.5(8) pm and Cr–D distances in the range 172.9(7) pm ≤ d(Cr–D) ≤ 182.4(8) pm.

Quality of Enriched Liquid Organic Fertilizer from Dairy Cattle Wastes on Closed Agriculture System

Liquid organic fertilizer (LOF) supplementation for solid organic fertilizer can accelerate the availability of plant nutrients. However, the nutrient content of LOF is highly dependent on its sources. The objective of the experiment was to examine the nutrient content of enriched liquid organic fertilizer from dairy cattle wastes. The experiment was conducted at Closed Agriculture Production System Research Station located in Air Duku Village, Bengkulu, Indonesia, at 1054 m above sea level. The experiment was laid out in a Completely Randomized Design with ten treatments and three replications. The treatments consisted of LOF from dairy cattle wastes enriched with Tithonia diversifolia, Ageratum conyzoides, Leucaena leucocephala, and Gliricidia sepium, their combination with phosphate rock, the combination of Tithonia diversifolia, and Ageratum conyzoides, and control. The LOF solution was anaerobically incubated for six weeks. The experiment indicated that during the incubation, solution pH declined for the first two weeks, gradually increased up to week 6. At the end of incubation, control exhibited the highest pH as compared to those with enrichment, indicating that decomposition of green biomass released a considerable amount of hydrogen. Enrichment of LOF considerably increased the contents of C, N, P, K, Ca, and Mg. The addition of phosphate rock to biomasses did not contribute a prominent increase in phosphorus content, possibly due to its low solubility at high pH. LOF enrichment with Tithonia diversifolia and Ageratum conyzoides had the highest N, P, and Mg contents. Therefore, the enrichment is the most potential for LOF production in closed agriculture system.

Modelling and simulation of a heaving wave energy converter based PEM hydrogen generation and storage system

The research on wave energy systems has been ongoing for decades. However, there are not many operational wave energy converters in use. The hydrogen energy systems also have a great potential. The proposed solution is to combine wave energy system with hydrogen energy system. The study provides details of simulation models and related simulation results. It is environmentally friendly, safe, feasible and effective. The results indicate that the proposed system model has a very high potential. With the use of low to medium energy density sea states, it is appears to be possible to generate (for DS1, DS2 and DS3, mH2 = 350.8 kg, 623.9 kg and 2124 kg, respectively) a considerable amount of hydrogen in 20-min. The presented results include WEC motion properties, instantaneous and moving average value of other system parameters. The future promising simulations results indicate that next generation wave energy converter systems could be accompanied by hydrogen generation and storage systems.

Electrodeposition of Ternary Fe–W–H Alloys

Electrochemical deposition, structure, and properties of Fe–W alloys are studied. The alloys formed at a low current density are crystalline supersaturated solid solutions which are magnetic. At higher current densities, amorphous nonmagnetic alloys of the same composition are formed. As a result of treatment at 500–600°С, both amorphous and crystalline transform into a more equilibrium binary system, containing W solid solution in Fe and an intermetallic compound. The concentration of the remaining W in the solid solution was much higher than the equilibrium solubility. A considerable amount of hydrogen incorporates into the deposits. The deposits may be qualified as ternary Fe–W–H alloys. The incorporated hydrogen plays a crucial role in the transition from a crystalline state typical for specimens produced at low current densities to the amorphous or nanocrystalline deposits formed at higher current densities.

Electrolysis of humidified methane to hydrogen and carbon dioxide at low temperatures and voltages

Considerable amounts of hydrogen are produced from fossil fuels. In recent years, natural gas and biogas have received attention as important feedstocks for hydrogen production, because methane, their main component, is hydrogen rich and readily available. Methane steam reforming is the major industrial route for hydrogen production, but requires high temperature due to endothermic nature of the reaction. This report presents a new green technology for the efficient and ecological production of hydrogen from methane. A humidified methane was electrolyzed to hydrogen and carbon dioxide at low onset cell voltages (ca. 0.3–0.4 V), depending on the temperature (150–250 °C). Almost all currents were used for the production of hydrogen and carbon dioxide. Hydroxyl radicals generated from water vapor during the electrolysis played an important role as an active oxygen for the methane oxidation reaction at the anode. This is the first report on the production of hydrogen from methane at both low temperatures and voltages.

Hydrogenation of the wide-gap oxide semiconductor as a room-temperature and 3D-compatible electron doping technique

A hydrogen atom, characterized by one unpaired electron and the smallest atomic radius, underlies the operations of various solid-state devices such as transistors, capacitors, solar cells, etc. Given its specific character as donor impurity in oxides, hydrogen may also facilitate efficient electron doping in a wide range of oxide devices. Here, we demonstrate room-temperature electrochemical hydrogenation of an archetypical oxide semiconductor (TiO2) thin film to achieve a 3D-compatible electron doping technique. The hydrogenated region can be precisely defined by photolithography without the influence of polycrystalline grain boundaries. Besides, secondary ion mass spectroscopy with deuterium isotope reveals considerable amount of hydrogen condenses around the TiO2 bottom interface indicating the critical influence of the interface on hydrogen stability. This hydrogen shows excellent stability in contrast to its high diffusivity in bulk TiO2, enabling robust electron doping for oxide thin film devices as well as suggesting stable interface hydrogen reservoir for electrochemical phenomena.

FexCo1−x-doped titanium oxide nanotubes as effective photocatalysts for hydrogen extraction from ammonium phosphate

Theoretically, tri-ammonium phosphate (NH4)3PO4 embeds considerable amount of hydrogen. Typically, the expected hydrogen release from this cheap and stable material is 73.83 mmol/gsalt if a proper catalyst is exploited in the hydrolysis reaction. In this study FexCo1−x-doped titanium oxide nanotubes are introduced as an efficient photocatalyst under solar radiation. The introduced modified titanium oxide nanotubes have been prepared in two successive steps. First, Na-doped TiO2 nanotubes were synthesized by hydrothermal treatment in presence of 10 N NaOH solution at 160 °C for 16 h. Then, doping by the proposed metals was carried out by ion exchange process in a microwave oven. X-ray photoelectron microscopy (XPS) and transmission electron microscopy (TEM) confirmed the success of the doping process and the nanotubular morphology, respectively. Study the photo characteristics indicated that the proposed metal doping shifted the band gap from UV to the visible light region as the estimated band gap energies for the as-prepared and doped nanotubes were 3.4 and 2.1 eV, respectively. Moreover, distinct enhancement for the visible light absorption capacity was observed. Accordingly, a distinguished improvement in the photocatalytic activity toward tri-ammonium phosphate hydrolysis was observed. However, the two metals content has a strong influence on the amount of the obtained hydrogen per gram of tri-ammonium phosphate salt. Numerically, the maximum obtained hydrogen was 4.0, 11.2, 11.2, 11.6, 13.4, 16.5, 17.4, 13.4 and 9.8 mmol/gsalt for the pristine TiO2, and FexCo1−x-doped TiO2 with x = 1, 0.8, 0.6, 0.5, 0.4, 0.3, 0.2, and 0.0, respectively.

Methane and hydrogen in hyperalkaline groundwaters of the serpentinized Dinaride ophiolite belt, Bosnia and Herzegovina

Methane (CH4) in continental serpentinized peridotites (MSP) has been documented in numerous hyperalkaline (pH > 9) springs and gas seeps worldwide. With a dominantly abiotic origin, MSP is often associated with considerable amounts of hydrogen (H2), produced by serpentinization. Both gases may fuel microbial activity in igneous rocks and may have played roles in the origin of life. MSP is also a natural CH4 source for the atmosphere, not included in the global greenhouse-gas budget, yet. Here we document a new and major case of MSP, in the Dinaride ophiolite belt in Bosnia and Herzegovina. CH4 is dissolved (83–2706 μM) in low temperature (13–30 °C), hyperalkaline (pH 10 to 12.8) waters in six sites, sampled through springs and boreholes. Four sites (Slanac, Vlajići, Kulaši and Lješljani) show CH4 isotopic signatures typical of abiotic MSP (δ13C: −18.5 to −35.7‰; δ2H: −221 to −335.4‰); two sites (Vaićeva and Kiseljak) show a dominantly biotic signature (δ13C: −58.8 and −65.1‰; δ2H: −310.8 and −226.8‰), probably due to mixing with gas from coal-beds adjacent to the ultramafic rocks. H2 concentration is highly variable (up to 348 μM), ethane, propane and butane reach 0.13 vol.% in total, and helium isotopic composition (R/Ra: 0.12 to 0.48) reflects a dominant crustal signature. The Lješljani site features the highest pH (12.8) and CH4 emission (∼9 ton y−1) in peridotite-hosted hyperalkaline groundwater documented so far. Geological and geochemical data converge towards the hypothesis that, as proposed in similar cases, CH4 was mainly generated by Sabatier reaction between H2 (from serpentinization) and CO2 (from C-bearing rocks, in tectonic contact with the ophiolite, or other CO2 sources). CH4-H2-H2O disequilibria and Sabatier reaction constraints suggest that CH4 is not formed in the hyperalkaline water, but in water-free or unsaturated rocks hosting opportune metal catalysts (e.g., chromitites). The amount of methane released to the atmosphere from individual springs is comparable to that of conventional biotic gas seeps/springs in sedimentary basins.

Biophotolysis-based hydrogen and lipid production by oleaginous microalgae using crude glycerol as exogenous carbon source

Microalgae are known as potential biofuel producers due to their high theoretical light conversion efficiencies. To develop simultaneous production process of hydrogen and lipids, several oleaginous microalgae were screened for their ability to produce hydrogen using crude glycerol as a low-cost exogenous carbon source. All microalgae could grow on crude glycerol and accumulated high content of lipids (>20%), but only Chlorella sp. produced considerable amount of hydrogen under anaerobic condition. The optimal conditions for hydrogen and lipid production by this microalga were: crude glycerol at glycerol concentration of 16 g/L, initial pH 6.8 and light intensity of 48 μmol photon m−2 s−1. These conditions gave the maximum hydrogen production of 10.31 ± 0.05 mL/L in serum bottle and 11.65 ± 0.65 mL/L in 1 L bioreactor along with lipid content >40% in the recovered microalgal biomass. Exploring biohydrogen production coupled with lipid production by oleaginous microalgae may contribute greatly to the sustainable production of biofuels by microalgae.

Evaluation of the effect of V4C3 precipitates on the hydrogen induced mechanical degradation in Fe-C-V alloys

The impact of V4C3 precipitates on the sensitivity to hydrogen embrittlement is evaluated in this work. Two main conditions are compared with each other, i.e. an as-quenched and a quenched and tempered condition in which carbides have precipitated. Tensile tests are performed on both uncharged and hydrogen charged specimen and a correlation with the amount of charged hydrogen is made by hot/melt extraction. The tempered induced carbides trap a significant amount of hydrogen which explains why the degree of hydrogen embrittlement increases for the quenched and tempered condition. To verify at which trapping sites hydrogen is located, thermal desorption spectroscopy is performed. A considerable amount of hydrogen is trapped in a rather irreversibly way, which still has an effect on the degree of hydrogen embrittlement. Additionally, a slightly modified temper treatment is applied to vary the carbide size and hence evaluate the impact of the hydrogen induced ductility loss.