Hydrogen Release Rate Research Articles

Electrochemical and In Vitro Biological Evaluation of Bio-Active Coatings Deposited by Magnetron Sputtering onto Biocompatible Mg-0.8Ca Alloy.

The use of resorbable magnesium alloys in the design of implants represents a new direction in the healthcare domain. Two main research avenues are currently explored for developing or improving metallic biomaterials: (i) increase of their corrosion resistance by designed compositional and structural modifications, and (ii) functionalization of their surfaces by coating with ceramic or polymeric layers. The main objective of this work was to comparatively assess bio-functional coatings (i.e., highly-crystallized hydroxyapatite and silica-rich glass) deposited by radio-frequency magnetron sputtering (RF-MS) on a biodegradable Mg-0.8Ca alloy (0.8 wt.% of Ca). After probing their morphology (by scanning electron microscopy) and structure (by Fourier transform infrared spectroscopy and grazing incidence X-ray diffraction), the corrosion resistance of the RF-MS coated Mg-0.8Ca substrates was electrochemically tested (in synthetic biological media with different degrees of biomimicry), and their cytocompatibility was assessed in osteoblast and fibroblast cell cultures. By collective assessment, the most promising performances, in terms of mass loss (~7% after 12 days), hydrogen release rate (~6 mL/cm2 after 12 days), electrochemical corrosion parameters and cytocompatibility, were obtained for the crystalline HA coating.

Study on the liquid phase-derived activation mechanism in Al-rich alloy hydrolysis reaction for hydrogen production

Bulk Al-Ga-In-Sn alloys are potential on-demand hydrogen generation materials, and Ga, In, and Sn with fascinating liquid characteristics manifest extraordinary activation capabilities in an Al–H2O reaction for hydrogen production. In the present work, the hydrogen production performances of Al-rich alloys were explored and the corresponding activation mechanism was investigated. The actual composition of the grain boundary (GB) phase in each alloy was determined by the Ga-In-Sn ternary phase diagram. A significant morphological transformation in the grain boundary particles (GBPs) was observed. Based on the surface tension of GBPs, the “Marangoni effect” was used to explain the hydrogen release rates of different alloys during hydrolysis. In addition, a liquid phase-derived activation mechanism during Al hydrolysis was proposed. The as-cast Al-Ga-In-Sn alloys were also used as energy carriers, and the power-consuming load was successfully supplied through the on-demand hydrogen supply mode, verifying the feasibility of liquid phase-activated Al-rich alloys in hydrogen energy applications.

Cu0.33@Co0.22Ni0.45 core–shell nanoparticles as hydrogen generation catalysts via hydrolysis of ammonia borane

A Cu0.33@Co0.22Ni0.45 core–shell nanocatalyst was produced for hydrolysis of ammonia borane and hydrogen generation. The catalyst has high hydrogen release rate, low activation energies, high cycle performance and excellent structural stability.

Disposable hydrogen generators: Magnesium hydride oxidation in aqueous salts solutions

The impact of mechanochemical activation and methods of addition of non-hydrolyzing salts of NaCl, NH4Cl, NH4Br и MgCl2∙(either dry powder or solution) on the reaction rate and yield of hydrogen production upon magnesium hydride oxidation by water was investigated. It was established that addition of halides increases the hydrogen yield from 22% to 99% (of theoretical value) while the rate of hydrogen production has increased from ∼220 to 1700 mL/min g (MgH2). The addition of dry salts during the mechanochemical treatment of the hydride always results in much higher reaction rate compared to the use of the same salt solutions. It was observed that activation by NH4Cl and MgCl2 results in bell-shaped change in the hydrogen release rate. Of all evaluated halide salt activators, the greatest overall yield (∼99%) was achieved in the presence of 0.17 M NaCl solution. The reaction rate at these conditions was rather slow; it took up to 4 h to complete the oxidation. The highest rate of oxidation, when 94% of theoretical yield was achieved in 3 min, was observed in the presence of 0.85 M NH4Br.

Bioactivity and <italic>in</italic> <italic>vitro</italic> degradation behavior of MgZnCa thin-film metallic glass

<p indent="0mm">Magnetron sputtering was used to prepare MgZnCa thin-film metallic glass (MG), and a single roller melt-spinning method was used to prepare amorphous MgZnCa ribbon. Potential polarization curves of MgZnCa amorphous ribbon and bulk high-purity magnesium (HP Mg) in simulated body fluids were compared using electrochemical tests. The corrosion resistance of MgZnCa MG is found to be significantly better than that of HP Mg, which is mainly attributed to its higher corrosion potential and lower corrosion current density. Immersion experiments, hydrogen evolution experiments, X-ray diffraction, Raman spectroscopy, and scanning electron microscopy were used to analyze the structure and composition of MgZnCa thin-film MG (TFMG) before and after corrosion, showing that the release rate of hydrogen was the fastest in the first hour, with active magnesium and calcium on the film’s surface preferentially dissolved. Furthermore, the appearance of a zinc-rich phase in the corrosion film and the increase in local pH promotes the precipitation of phosphate, which can improve the corrosion resistance of MgZnCa MG. <italic>In</italic> <italic>vitro</italic> experiments show that the 25% concentration extract obtained after soaking the MgZnCa MG has higher cell viability and lower apoptosis rate than the control medium, indicating that the MgZnCa MG is biocompatible. Therefore, with excellent corrosion resistance and biocompatibility, MgZnCa MG can be used as bioactive coatings on the surface of biologically inert materials.

Experimental and theoretical study on dissociation thermodynamics and kinetics of hydrogen-propane hydrate

Hydrate-based hydrogen storage is a promising technology in the clean energy field. In this study, propane was selected as the accelerator guest molecule for hydrogen storage in hydrates. Hydrogen–propane (0.67/0.33, mole ratio) hydrate dissociation properties are investigated by experiment and molecular dynamics simulation. The hydrogen–propane hydrate phase equilibrium is measured by different methods and the average dissociation heat is 77.03 J/g under 0.98–1.72 MPa. While hydrate dissociation heat flow curves show the characteristic of two-step dissociation, which is further confirmed via Raman spectroscopy. Simultaneously, hydrogen–propane hydrate dissociation driven by depressurization and heating are also investigated by Raman spectroscopy. During dissociation, the Raman peak area of hydrogen in hydrate continues to decrease, whereas it is relatively stable for propane before the hydrate dissociation complete. In addition, hydrogen–propane hydrate reformation occurs more intensely during the heating process, especially when the temperature exceeds 273 K than with depressurization. This indicates that depressurization is more feasible for continuous hydrogen releasing, a concept of recycling hydrate clathrate structure was proposed to shorten hydrate formation time and accelerates hydrogen storage rate. In addition, the molecular dynamics simulation results confirmed that the hydrogen release rate from hydrate is higher than that of propane from the microscopic view point. The results of this study provide a potential pathway of hydrogen storage using hydrates.

Interstitial carbon doped of setaria viridis-like Znln2S4 hollow tubes for efficient the performance of photocatalytic hydrogen production

In the photocatalytic water splitting hydrogen production system, the key to efficient use of solar energy is to choose a suitable photocatalyst. As an important ternary sulfide, ZnIn2S4 (ZIS) has attracted wide attention because of its narrow band gap (Eg = 2.3–2.8 eV) and wide light absorption range. However, further modification was still needed. Therefore, in this work, the unique C/ZIS hollow tubes with nano-flakes were prepared by a simple solvothermal method. To a large extent, this unique structure increased the utilization of light and active sites. Moreover, the dissolution of PAN during the solvothermal process caused the carbon element to be uniformly doped into the hollow tube framework. After a series of characterization results, C/ZIS-3.0 has the best hydrogen release rate (1241.94 μmol g−1 h−1) and good cyclability under visible light irradiation (λ ≥ 420 nm). And its unique morphology and possible catalytic mechanism were further discussed.

Cycling performance for storage and purification of lanthanum‐rich mischmetal alloy in the presence of hydrogen sulfide

AbstractWith the continuous expansion of the high‐purity hydrogen application range, the performance degradation of hydrogen storage alloy (HSA) caused by impurities has attracted widespread attention in producing pure hydrogen from biomass. In this study, the lanthanum‐rich mischmetal alloy's purification ability on hydrogen sulfide impurities and cycling performance were studied. The hydrogen with different concentrations of hydrogen sulfide was used to investigate the purification performance, which assumes the gas derived from biomass. Besides, a cycling experiment was designed to analyze cycling performance. The results show that the HSA could remove high concentrations of hydrogen sulfide entirely. It was also found that impurities of 1 ppm hydrogen sulfide had little effect on the HSA. With hydrogen sulfide concentrations of 100 ppm, the hydrogen storage capacity, absorption rate, and release rate were reduced, but they became a stable state from the second cycle. The performance degradation mechanism was analyzed by Energy Dispersive X‐Ray Spectroscopy (EDS) and X‐ray Photoelectron Spectroscopy (XPS​).

Effects of Milling in Hydrogen on Magnesium Hydride with a Hydride-Forming Titanium Additive

A hydride-forming element titanium (Ti) was selected as an additive to improve the hydrogen uptake and release properties of MgH2. The hydrogen uptake and release properties of three Ti-added MgH2 alloys [named MgH2-xTi (x = 6, 12, and 15)] prepared by milling in hydrogen (reactive mechanical grinding) were investigated and those of MgH2-12Ti were studied in more detail because it had the highest initial hydrogen uptake and release rates and the largest quantities of hydrogen absorbed and released for 60 min. At the cycle number, n, of one (n = 1), MgH2-12Ti absorbed 4.01 wt.% H for 2.5 min and 6.39 wt.% H for 60 min at 573 K in 12 bar H2, having an effective hydrogen storage capacity of 6.39 wt.%. MgH2-12Ti released 0.44 wt.% H for 2.5 min and 1.86 wt.% H for 60 min at 593 K in 1.0 bar H2. γ-MgH2, TiH1.924, and MgO were formed during reactive mechanical grinding. We believe that the brute forces and tensile, compressive, or shear stresses, which are applied to the materials during reactive mechanical grinding, introduce imperfections, fabricate cracks, expose fresh and clean surfaces, decrease the particle size, and disperse the additive among the particles. The γ-MgH2, TiH1.924, and MgO formed during reactive mechanical grinding and their pulverization during reactive mechanical grinding are believed to make these effects stronger.

The Effect of Graphite and Fe2O3 Addition on Hydrolysis Kinetics of Mg-Based Hydrogen Storage Materials

In this paper, graphite and Fe2O3 are introduced into MgH2 powder by the method of hydrogenation after magnetic grinding. Hydrogen storage materials which composite of MgH2–5 wt.% C and MgH2–5 wt.% C–5 wt.% Fe2O3 are successfully prepared. The physical structure of these materials was analyzed and characterized by XRD, SEM, etc. Furthermore, the influence of graphite and Fe2O3 on the hydrolysis of MgH2 was systematically investigated. The results show that MgH2–C–Fe2O3 composite powder has the fastest hydrogen release rate in municipal drinking water and the highest conversion rate. Graphite and Fe2O3 can effectively reduce the activation energy of the hydrolysis reaction of MgH2 and improve the hydrolysis kinetics of MgH2. The synergistic effect of the coaddition of graphite and Fe2O3 can significantly increase the hydrolysis conversion rate of MgH2 and improve the hydrolysis kinetics.

Study on Hydrolysis of Magnesium Hydride by Interface Control

Magnesium hydride (MgH2) is one of the competitive hydrogen storage materials on account of abundant reserves and high hydrogen content. The hydrolysis of MgH2 is an ideal and controllable chemical hydrogen generation process. However, the hydrolyzed product of MgH2 is a passivation layer on the surface of the magnesium hydride, which will make the reaction continuity worse and reduce the rate of hydrogen release. In this work, hydrogen generation is controllably achieved by regulating the change of the surface tension value in the hydrolysis, a variety of surfactants were systematically investigated for the effect of the hydrolysis of MgH2 In the meantime, the passivation layer of MgH2 was observed by scanning electron microscope (SEM), and the surface tension value of the solution with different surfactants were monitored, investing the mechanism of hydrolysis adding different surfactants. Results show that different surfactants have different effects on hydrogen generation. The hydrogen generation capacity from high to low is as follows: tetrapropylammonium bromide (TPABr), sodium dodecyl benzene sulfonate (SDBS), Ecosol 507, octadecyl trimethyl ammonium chloride (OTAC), sodium alcohol ether sulfate (AES), and fatty methyl ester sulfonate (FMES-70). When the ratio of MgH2 to TPABr was 5 : 1, the hydrogen generation was increased by 52% and 28.3%, respectively, at the time of 100 s and 300 s. When hydrolysis time exceeds 80 s, the hydrogen generation with AES and FMES-70 began to decrease; it was reduced by more than 20% at the time of 300 s. SEM reveals that surfactants can affect the crystalline arrangement of Mg(OH)2 and make the passivation layer three-dimensionally layered providing channels for H2O molecules to react with MgH2.

Hierarchically porous CoP@CNR nanorod derived from metal-organic frameworks as noble-metal-free catalyst for dehydrogenization of ammonia-borane

The development of effective and inexpensive catalysts for hydrogen release from hydrogen-storage compounds such as ammonia-borane (AB) is crucial in academic and industrial fields for the reduction of greenhouse gas emissions. Herein, we report a facile method to fabricate well-dispersed CoP nanoparticles (NPs) with an average particle size of 4.3 nm. The CoP NPs were encapsulated in carbonaceous nanorods (CoP@CNR) using metal-organic frameworks (MOFs) as a sacrificial precursor. The CoP@CNR catalysts were characterized, and their catalytic performance for the dehydrogenization of AB at 25 °C in an alkaline solution was determined. CoP@CNR (400) with a hierarchically meso-microporous structure (micropore area = 73.6 m2 g-1 and micropore volume = 0.19 cm3 g-1) and a specific surface area of 88.4 m2 g-1 was synthesized during the phosphorization process. The hierarchically porous structure was instrumental in immobilizing metal NPs and accelerating mass diffusion. Moreover, the incorporation of P into Co NPs modified the electronic structure of the latter and accelerated the dehydrogenization of AB. This resulted in a hydrogen release rate of 10,014 mL/(min·g), which was 13 times higher than that of the pure Co nanocatalyst. In addition, we reported the kinetic studies for AB hydrolysis catalyzed by CoP@CNR (400) in terms of the temperature effect, isotope effect, catalyst concentration, AB concentration, and NaOH concentration.

Analysis of blister-like morphology on the oxide film of Zr-1Nb alloy corroded in lithiated water

Zr-1Nb alloy performs desired corrosion resistance in deionized water but shows accelerated corrosion in lithiated water. However, the degradation mechanism of Zr-1Nb alloy in lithiated water is still unclear. In this work, blister-like morphologies on the oxide film of the Zr-1Nb alloy corroded in lithiated water was observed, providing a direct evidence to the hydrogen generation beneath the oxide film. The formation of blisters was analysed from the perspectives of blister morphology and hydrogen uptake behaviour. A high hydrogen release rate contributes to the formation of blisters and degrades the protectiveness of oxide film and corrosion resistance after corrosion transition.

The effects of low-temperature phenomena on rapid phase transition of liquid hydrogen

The simultaneous rise in hydrogen economy and cryogenic liquefaction techniques for long-distance storage and transportation has incentivized the development of technological solutions based on the liquefied hydrogen. However, detailed models accounting for the peculiar phenomena of this cryogenic system in the case of accidental release, namely cryogenic evaporation rate and para-ortho transformation, are necessary before large-scale commercialization. In this light, this work aims to unravel this gap of knowledge on safety aspects involving liquid hydrogen through a numerical approach. More specifically, the top events that arose from the accidental release of liquid hydrogen in the absence of ignition have been modeled. A proper evaporation sub-model suitable for cryogenic conditions has been selected in accordance with the literature. The quantum mechanics approach was adopted to estimate the thermodynamic properties of the hydrogen configurations accurately. These estimations were compared with data from the literature, showing excellent agreement. The effect of para-ortho transformation was evaluated by implementing the obtained database. Besides, different releasing surfaces and materials were tested, either solid (e.g., concrete) or liquid (i.e., water), resulting in hydrogen release rate ranging from 2.00×10−4 – to 13.90 kg/s). The generated over-pressures were calculated for all the investigated cases and critically compared with numerical data obtained in this work and analytical model retrieved from the current literature. These results indicate that neglecting the para-ortho transformation represents a non-conservative hypothesis. Indeed, peaks potentially producing significant structural damages were observed only in cases where this transformation was considered.

The mechanical and corrosion resistance of Mg-Zn-Ca-Ag alloys: the influence of Ag content

Biomedical magnesium alloys have become an ideal material for degradable implants because of their similar density and elastic modulus with human bone. In this study, Mg-3Zn-0.2Ca-xAg (x = 0%, 0.1%, 0.3%, 0.5%, 0.7%, wt.%) alloys were fabricated to enhance the comprehensive properties of the Mg-3Zn-0.2Ca (wt.%) alloys. The microstructure shows that the alloy possesses relatively smaller grain size of 2.08 μm when the addition of Ag is 0.3 wt.%. The Mg-3Zn-0.2Ca-0.3Ag also owns the best mechanical properties whose elongation, yield strength and tensile strength are 4.57%, 5.7%, and 2.4%, respectively, higher than that of Mg-3Zn-0.2Ca. The electrochemical experiments shows that Mg-3Zn-0.2Ca-0.3Ag has lower corrosion current density (30.5 μA/cm2), which indicates that its corrosion resistance has been improved. After immersed in simulated body fluids at 37 ℃ for 15 days, the hydrogen release rate and degradation rate of the Mg-3Zn-0.2Ca-0.3Ag is significantly lower than that of Mg-3Zn-0.2Ca. In addition, the cytotoxicity test with L 929 cells shows that Mg-3Zn-0.2Ca-0.3Ag alloy has good biocompatibility.

Thermal coupling of an open-cathode proton exchange membrane fuel cell with metal hydride canisters: An experimental study

In this paper, the impacts of utilising the heat generated by a 2.5-kW open-cathode proton exchange membrane fuel cell (PEMFC) on enhancing the hydrogen release rate of nine 800 NL AB5 metal hydride (MH) canisters were experimentally investigated. Thermal coupling of MH canisters with PEMFC offers a potential to improve the hydrogen discharge rate of MH canisters by utilising its waste heat. However, the added complexity for implementing this idea remains to be a barrier. Open-cathode fuel cells with hot air exiting the cathode side offer an opportunity to simplify its thermal coupling arrangement with MH canisters. The set-up was designed with minimum added parts with just a ducting system to direct the hot exit air from the fuel cell passing over the MH canisters. The experimental results showed that the heat required by the MH canisters to supply enough hydrogen to the fuel cell at 500 W, 1000 W and 2000 W operating points accounts for around 40%, 36.5%, and 32% of the total heat removal from the stack, respectively. The arrangement proved to be feasible for serving its purpose and could eliminate the need for oversizing the MH hydrogen storage system that is normally practised to guarantee the right rate of hydrogen supply at higher power outputs.

Nanoconfinement of Molecular Magnesium Borohydride Captured in a Bipyridine-Functionalized Metal-Organic Framework.

The lower limit of metal hydride nanoconfinement is demonstrated through the coordination of a molecular hydride species to binding sites inside the pores of a metal-organic framework (MOF). Magnesium borohydride, which has a high hydrogen capacity, is incorporated into the pores of UiO-67bpy (Zr6O4(OH)4(bpydc)6 with bpydc2- = 2,2'-bipyridine-5,5'-dicarboxylate) by solvent impregnation. The MOF retained its long-range order, and transmission electron microscopy and elemental mapping confirmed the retention of the crystal morphology and revealed a homogeneous distribution of the hydride within the MOF host. Notably, the B-, N-, and Mg-edge XAS data confirm the coordination of Mg(II) to the N atoms of the chelating bipyridine groups. In situ 11B MAS NMR studies helped elucidate the reaction mechanism and revealed that complete hydrogen release from Mg(BH4)2 occurs as low as 200 °C. Sieverts and thermogravimetric measurements indicate an increase in the rate of hydrogen release, with the onset of hydrogen desorption as low as 120 °C, which is approximately 150 °C lower than that of the bulk material. Furthermore, density functional theory calculations support the improved dehydrogenation properties and confirm the drastically lower activation energy for B-H bond dissociation.

Insight into the indium-related morphology transformation and application for hydrogen production of Al-rich alloys

Al-Ga-In-(Sn) alloys with different indium (In) content were prepared by the traditional high-temperature melting technique. The compositions and microstructures of alloys are studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). We found that free indium presented in alloys plays vital role in morphology transformation of grain boundary (GB) phase particles and associated hydrogen production performance of alloys. As In dosage increasing, the numerous irregular bar-like particles instead of granular particles (mainly composed of In3Sn) were observed in alloys with GB phase which mainly composed of free indium (combined with XRD and EDS analysis). Meanwhile, the content and distribution of aluminum (Al) contained in GB phase particles have been somewhat neglected by the wider researchers. In this work, we provide a comprehensive study in relevant fields how Al atoms can contribute to morphology transformation process of GB phase particles. The hydrogen production performance tests were completed by gas mass flowmeter at 40 °C. The results show that the hydrogen release rate of the as-cast alloys gets significantly decreased with the increase of In dosage in alloys, which enables applications of effective on-demand hydrogen supply.

Controllable synthesized heterojunction hollow nanotube of g-C3N4/CdS: Enhance visible light catalytic performance for hydrogen production

Photocatalytic splitting water is a new clean green technology that has become a research hotspot in the scientific community. Among them, cadmium sulfide (CdS) is a classic photocatalyst. But applications are limited due to photo-corrosion and fast electron-hole recombination. Herein, hollow CdS tubes with special morphology were successfully modified by simple vapor deposition of graphitic carbon nitride (CN). The obtained 1D binary heterojunction photocatalyst showed good photohydrolysis hydrogen production performance under visible light (λ ≥ 400 nm). The introduction of CN prevented photo-corrosion of CdS, so it also had great cycle performance. At the same time, the proper amount of CN deposition was studied. The most suitable sample (CN0.5-CdS) showed the best hydrogen release rate (392.84 μmol g−1 h−1) within 4 h. Finally, based on a series of analysis datas of photocatalysts, its special tubular structure and possible catalytic mechanism were further discussed.

Analysis of ignition delay by taking Di-tertiary-butyl peroxide as an additive in a dual fuel diesel engine using hydrogen as a secondary fuel

Ignition delay (ID) is one of the important parameters that make influenced on the combustion process inside the cylinder. This ignition delay affects not only the performances but also the noise and emissions of the engine. In this regards the experiments were conducted on single cylinder 4–stroke compression ignition research diesel engine, power 3.50 kW at constant speed 1500 rpm Kirloskar model TV1 with base fuel as diesel and hydrogen as secondary fuel with and without Di-tertiary-butyl-peroxide (DTBP). Experiments were conducted to measure the ignition delay of the dual fuel diesel (DFD) engine at different load conditions and substitution of diesel by hydrogen with or without DTBP and then it was compared with predicted ID given by Hardenberg-Hase equation and modified Hardenberg-Hase equation.The experimental values of ignition delay were compared with theoretical ignition delay which was predicted on the basis of Hardenberg-Hase equation by considering mean cylinder temperature, pressure, activation energy and cetane number and variations are found in between 6.60% and 21.22%. While, the Hardenberg-Hase equation was modified (by considering variation in activation energy) for DFD engine working on diesel as primary fuel and hydrogen as secondary fuel shows variations 1.20%–11.96%. Furthermore, with DTBP it gives variation up to 18.01%. It was found that ID decreases with increase in percentage of DTBP and hydrogen in air-fuel mixture. This might be due to the cetane improver nature of DTBP, pre-ignition reaction rate and energy release rate of hydrogen fuel. The polytropic index get increased by addition of (Di-tert butyl peroxide) DTBP. Similarly, 5% Di tertiary butyl peroxide reduces Ignition delay.