Hydrogen production by aluminum corrosion in hydrochloric acid and using inhibitors to control hydrogen evolution

This study reports on the systematic assessment of hydrogen (H₂) production by corrosion of aluminum alloy (AA) in hydrochloric acid (HCl) at different temperature. Rare earth inhibitors, lanthanum (La) and cerium (Ce) have been applied to control the H₂ production process. The production process is based on electrochemical reaction of aluminum (anodic reaction) in the HCl solution, which has a high concentration of hydrogen ions (H⁺), the H⁺ ions are reduced and H₂ is evolved. Preliminary results showed that an increase in temperature of working solution produced an increase of the H₂ production rate. The H₂ production rate increases because acid can prevent aluminum passivation during H₂ evolution. The rare earth inhibitors La and Ce control the H₂ evolution, especially, when using mixture of both inhibitors. This result demonstrates a synergistic effect between the La and the Ce inhibitors. X-ray diffraction studies were performed on the surface structure before and after immersion, and a scanning electron microscope (SEM) was used to study the morphology of the AA.     

A novel method for generating hydrogen by hydrolysis of highly activated aluminum nanoparticles in pure water

A simple method with 100% efficiency for generating pure hydrogen in large scale by hydrolysis of highly activated aluminum in water was established. In this activation method, Aluminum is milled using salt particles (as nano-miller) with different salt to aluminum mole ratios. Due to their brittle nature, salt particles are fractured during milling and their sharp edges chop aluminum particles into pieces. This leads to an increment in hydrolysis kinetics. Meantime, salt particles are driven into newly created surfaces of aluminum particles, producing salt gates that will be removed in water environment, causing hydrogen generation reaction to proceed. The other product of reaction is aluminum oxide hydroxide (AlOOH) which is nature-friendly and can be easily separated from water. The highest average rate of hydrogen generation was 75 ml/min per 1 g of aluminum.     

Room-temperature hydrogen release from activated carbon-confined ammonia borane

In chemical hydrogen storage, nanoconfinement (or nanoscaffolding) is an efficient approach to reduce the size of the particles of boron hydrides such as ammonia borane (AB, NH₃BH₃) at nanoscale while destabilizing its molecular network. It involves the dehydrogenation of AB at temperatures lower than 100 °C and hinders the formation of undesired gaseous by-products such as borazine. Herein, commercial activated carbon (AC) with a specific surface area of 716 m² g⁻¹ and a porous volume of 0.36 cm³ g⁻¹ was used as host material for AB nanoconfinement. A composite activated carbon-ammonia borane (AC@AB) was successfully prepared by infiltration in cold conditions (0 °C). Its dehydrogenation was followed by volumetric method, FTIR, XRD, TGA, DSC, GC–MS and ¹¹B MAS NMR. The most striking result is that the nanoconfined AB, being highly destabilized, dehydrogenates in ambient conditions, even at 3–4 °C. It is demonstrated that dihydrogen is formed according to two pathways that simultaneously take place. The first one is the dehydrogenation through inter- and/or intra-molecular reactions between protonic H and hydridic H of AB, and the second one is the acid-base reaction between protonic H of COO−H groups present on the AC surface and hydridic H of AB.     

Hydrogen generation from water by means of activated aluminum

An important part of the hydrogen energy problems is the search of hydrogen sources for feeding hydrogen–air fuel cells. One of the most convenient methods for hydrogen generation is based on oxidation of aluminum by water. In this paper the method of aluminum activation based on the application of gallium alloys (gallams) is suggested.     

Improving hydrogen production from the hydrolysis of ammonia borane by using multifunctional catalysts

A novel multifunctional catalytic system has been developed for efficient hydrogen generation through the hydrolysis of ammonia borane. This system combines Pd NPs with acid sites and amines, which are both task-specific functionalities able to destabilize the N → B dative bond. The acidity of the support (zeolites of different structure and SiO₂/Al₂O₃ ratio) used to disperse the Pd NPs causes an increase in the hydrogen production rate. However, the positive effect of incorporating p-phenylenediamine in the catalyst is much more pronounced, causing a two-fold increase in the activity of the catalyst. The combined effect of the different functionalities yields excellent performance in the hydrolysis of ammonia borane, greatly enhancing the activity of the metal-based catalyst and reducing the activation energy of the catalyzed reaction.     

Preparation and characterization of activated aluminum powder by magnetic grinding method for hydrogen generation

In this paper, activated aluminum powder was prepared by magnetic grinding with a homemade equipment and hydrolyzed in alkaline solution to produce hydrogen. The results showed that the prepared aluminum powder could improve hydrolysis reactivity effectively and have high hydrogen yield in alkaline solution (up to 1340 mL/g). It was found that grinding time, reaction temperature and grinding media could significantly affect the hydrolysis reaction while alloy components had little effect. Aluminum powder ground for 40 min can produce hydrogen 1340 mL/g within 6 min under optimal reaction temperature of 323 K. Copyright © 2013 John Wiley & Sons, Ltd.     

Application of activated aluminum powder for generation of hydrogen from water

This work presents a parametric investigation of aluminum–water reaction to generate hydrogen, using a novel activated aluminum powder. An original thermo-chemical process involving a small fraction of a lithium-based activator enables a spontaneous reaction of the activated aluminum particles with water, which otherwise would not react due to the existence of an oxide or hydroxide surface layer. Experiments have shown that a fast, self sustained reaction of activated aluminum with water takes place even at room temperature and, for appropriate operating conditions, results in a practically 100% yield of hydrogen generation. The reaction rate may be controlled by the aluminum particle size, water temperature, metal activation conditions and metal/water mass ratio. The method demonstrates safe and compact hydrogen storage (11 wt% compared to the aluminum). Among its potential applications may be fuel cells, as well as automotive and marine propulsion.     

Hydrogen trapped at intermetallic particles in aluminum alloy 6061-T6 exposed to high-pressure hydrogen gas and the reason for high resistance against hydrogen embrittlement

Hydrogen (¹H) trapped at intermetallic particles (IPs) in an aluminum alloy, 6061-T6, was visualized with secondary ion mass spectrometry (SIMS) by precisely excluding the false signal which is caused by background hydrogen (H_BG). The interference of the H_BG was avoided by a unique continuous pre-sputtering (pre-digging) by a primary ion beam of SIMS into a sample in combination with silicon sputtering prior to the SIMS measurement of the sample and we succeeded in visualizing the exact signal of ¹H trapped by IPs at subsurface layer of the sample charged in high-pressure hydrogen gas. The thermal desorption analysis clarified that the desorption energy (E_d) of the IPs was 200 kJ/mol or higher, which was extremely higher than E_d for lattice interstice, dislocations, and vacancies. High density hydrogen was concentratedly trapped at IPs in the subsurface layer in contact with the hydrogen gas. This nature causes an extremely low effective hydrogen diffusivity of 6061-T6 of the order of 10^?14 m²/s even at 200 °C and may eventually give a high HE resistance to 6061-T6.     

Development and demonstration of a deployable apparatus for generating hydrogen from the hydrolysis of aluminum via sodium hydroxide

Emergency and backup power is often enabled through the use of petrochemical based fuels and combustion-based generator systems, and while reliable, these backup power systems fail when petrochemical supplies are disrupted due to refinery, oil outages, or transportation delays. Fuel cells in some cases can serve as a backup to these traditional generators, but they also are fuel-limited to supplies of available energy sources. Recent work conducted in our laboratories focused on the development of a “backup” emergency hydrogen generation system that could be employed when existing energy stockpiles have failed or depleted. Specifically, aluminum metal can be used to generate hydrogen for fuel cells via hydrolysis with sodium hydroxide. In this paper, we summarize the engineering work to produce a deployable aluminum to hydrogen generator which is capable of producing 3.75 kg of hydrogen per day from scrap aluminum feedstocks. The generator was built upon an aircraft deployable pallet, allowing for hydrogen to be generated remotely in cases of power and fuel outages.     

Feasibility of on-board hydrogen production from hydrolysis of Al-Fe alloy for PEMFCs

The feasibility of using the hydrolysis of Al alloys in an on-board hydrogen generation system for PEMFCs is investigated. Hydrogen produced by the hydrolysis of Al-Fe alloys is supplied directly to a PEMFC. The weight-normalized hydrogen generation rate of sheet Al-1Fe is higher than that of cubic Al-1Fe alloy, and its hydrogen generation rate changes little during hydrolysis in alkali water. Furthermore, during the hydrolysis reaction, the water temperature is stable. Hence, Al-1Fe in sheet form is suitable as a source for on-board hydrogen production from hydrolysis in alkali water. At a current of 10 A, the PEMFC presents a voltage of about 0.71 V, which remains stable for 37 min. However, after 37 min, the cell voltage decreases dramatically to 0 V due to a reduction in hydrogen feeding rate by exhaustion of Al-1Fe. It is particularly notable that on-board hydrogen production using the hydrolysis of Al-Fe alloy exhibits self-humidification, supplying humidity automatically without a humidifier.     

Formation of aluminium hydride (AlH3) via the decomposition of organoaluminium and hydrogen storage properties

Aluminium hydride (AlH₃) is a promising hydrogen storage material due to its competitive hydrogen storage density and moderate decomposition temperature. However, there is no convenient way to prepare/regenerate AlH₃ from (spent) Al by direct hydrogenation. Herein, we report on a novel approach to generate AlH₃ from the decomposition of triethylaluminium (Et₃Al) under mild hydrogen pressures (10 MPa) with the use of surfactants. With tetraoctylammonium bromide (TOAB), the synthesis led to the formation of nanosized AlH₃ with the known α phase, and these nanoparticles released hydrogen from 40 °C instead of the 125 °C observed with bulk α-AlH₃. However, when tetrabutylammonium bromide (TBAB) was used instead of TOAB, larger nanoparticles believed to be related to the formation of β-AlH₃ were obtained, and these decomposed through a single exothermic process. Despite the possibility to form α-AlH₃ under low conditions of temperature (180 °C) and pressure (10 MPa), TOAB stabilised AlH₃ was found to be irreversible when subjected to hydrogen cycling at 150 °C and 7 MPa hydrogen pressure.     

Innovative hydrogen release from sodium borohydride hydrolysis using biocatalyst-like Fe2O3 nanoparticles impregnated on Bacillus simplex bacteria

For the first time in this innovative study, microorganisms such as Bacillus simplex bacteria, mostly used in biological activity studies, are used as a bio-supporter agent of iron to release hydrogen from sodium borohydride hydrolysis at 25.0 ± 0.1 °C. The goal is to investigate thoroughly sodium borohydride hydrolysis catalyzed by Fe₂O₃ nanoparticles impregnated on microorganism such as Bacillus simplex (BS) bacteria (Fe₂O₃@BS NPs) known with strong antibacterial properties, which makes innovative them a candidate for hydrolysis reaction. This study was focused on the preparation, identification, and catalytic use of biocatalyst-like Fe₂O₃@BS NPs for hydrogen release from the sodium borohydride hydrolysis at 25.0 ± 0.1 °C. The characterization results made after and before hydrolysis reaction using by SEM/SEM-EDX, FT-IR, XRD, UV–vis, XPS, DLS, ELS Zeta potential, ESR, and TEM techniques reveal the formation of highly active, stable, durable, and long-lived biocatalysts-like Fe₂O₃@BS NPs.     

Design and development of a refrigeration system energized with hydrogen produced from scrap aluminum

Hydrogen holds out great promise as an energy source whose use does not pollute the environment. In this context, methods of hydrogen production which do not involve formation of carbon dioxide are especially attractive. The present work describes a cheap and versatile prototype of an alkaline hydrolyser which efficiently produces hydrogen from aluminum scrap and aqueous sodium hydroxide, the hydrogen produced being used directly to energize, by combustion, a refrigerator working on the ammonia–water principle, which was also designed and developed in our laboratory. A direct comparison of the system when energized by liquid-propane flame and by hydrogen flame shows a clearly better performance in the latter case, which produces a temperature of −20 °C after about 2 h of operation.     

Kinetics of cotton cellulose hydrolysis using concentrated acid and fermentative hydrogen production from hydrolysate

The kinetics of cotton cellulose hydrolysis using concentrated sulfuric acid and the performance of fermentative hydrogen production from the hydrolysate in the batch system was carried out in this study. Effects of sulfuric acid concentrations, cotton cellulose concentrations and operating temperatures on the cotton cellulose hydrolysis were investigated. It was found that cotton cellulose can dissolve completely in sulfuric acid concentration above 55% (by volume) at room temperature. The reduced sugar yields were varied from 64.3 to 73.9% (g R-sugar/g cotton cellulose) with the initial cotton cellulose concentrations of 30-70 g/L at a temperature of 40 °C.The reduced sugar concentrations and the initial pH of biohydrogen production were investigated at 37 °C. It was found that the optimal values of the hydrogen yield and substrate utilization were 0.95 mol H₂/mol R-sugar and 98% with an initial pH of 8.2, when substrate concentration was fixed at 20 g R-sugar/L. The maximum hydrogen yield was 0.99 mol H₂/mol R-sugar at a substrate concentration of 15 g R-sugar/L. Using the Gompertz Equation Model simulation, the maximum hydrogen production rate was 253 mL H₂/h/L at a substrate of 30 g/L and initial pH of 8.4.     

Multiscale study of the structure and hydrogen storage capacity of an aluminum metal-organic framework

First-principles calculations based on density functional theory and Grand Canonical Monte Carlo (GCMC) simulations are carried out to study the structure of a new Aluminum Metal-Organic Framework, MOF-519, and the possibility of storing molecular hydrogen therein. The optimized structure of the inorganic secondary building unit (SBU) of MOF-519 formed by eight octahedrally coordinated aluminum atoms is presented. The different storage sites of H₂ inside the SBU and the BTB ligand are explored. Our results reveal that the SBU exhibits two different favorable physisorption sites with adsorption energies of ?12.2 kJ/mol and ?1.2 kJ/mol per hydrogen molecule. We have also shown that each phenyl group of BTB has three stable H₂ adsorption sites with adsorption energies between ?6.7 kJ/mol and ?11.37 kJ/mol. Using GCMC simulations; we calculated the molecular hydrogen (H₂) gravimetric and volumetric uptake for the SBU and MOF-519. At 77 K and 100 bar pressure, the hydrogen uptake capacity of SBU is considerably enhanced, reaching 16 wt.%. MOF-519 has a high gravimetric uptake, 10 wt.% at 77 K and 4.9 wt.% at 233 K. It has also a high volumetric capacity of 65 g/L at 77 K and 20.3 g/L at 233 K, indicating the potential of this MOF for hydrogen storage applications.     

Bioaugmented cellulosic hydrogen production from cornstalk by integrating dilute acid-enzyme hydrolysis and dark fermentation

The cellulosic hydrogen production from cornstalk based on the integrating dilute acid with enzymatic hydrolysis was investigated using response surface methodology (RSM). The dilute acid pretreatment of cornstalk with the concentration of 1.5% H₂SO₄, 121 °C and 60 min was found to be most effective in the first prehydrolysis stage. Thereafter, the process parameters of enzymatic hydrolysis of the solid residue, which derived from acid-pretreated cornstalk, were further optimized by a three factor-five level central composite design (CCD) with temperature (X₁), pH (X₂), and enzyme loading (X₃) as the independent variables. The optimal parameters of enzymatic hydrolysis of substrate were observed to be 52 °C of temperature, pH 4.8 and 9.4 IU/g of enzyme loading. In this case, the total soluble sugar obtained in the hydrolysis stages was 562.1 ± 6.9 mg/g-TVS, and the maximum hydrogen yield from cornstalk by anaerobic mixed microflora was 209.8 ml/g-TVS. Biodegradation mechanism of cornstalk for hydrogen production was further discussed based on analyzing changes in the physical structure and chemical composition of cornstalk during the hydrolysis and fermentation processes.     

Influence of charging parameters on the effectiveness of electrochemical hydrogen storage in activated carbon

Carbonaceous material, if it is to compete with metallic hydride alloys as a hydrogen storage electrode in a reversible chemical power source, should demonstrate 2 key qualities. Firstly, it should exhibit a high hydrogen elecrosorption. Secondly, it should co-operate efficiently with the cathode under particular charging and discharge conditions. Based on this assumption, an investigation into the influence of charging conditions on storage efficiency of a lignin based active carbon electrode with high hydrogen storage capacity was undertaken. Current densities of up to 32 A/g and charging times ranging from 196 seconds to 48 h were used. The results show that it is possible to charge the electrode rapidly even for tens of seconds using adequately high current density. However, full exploitation of charge storage capability of the carbon material (585 mA h/g in the tested material [the equivalent of storing 2.17 wt% in gas hydrogen]), required significant overcharge and, therefore, was only possible at a very low coulombic efficiency – below 2%. The acceptable coulombic efficiency of the charge/discharging process – 60%, could only be reached provided that less than 50% of the maximum material sorption capacity was utilized.     

Experimental investigation of solar assisted hydrogen production from water and aluminum

Sustainable production of hydrogen at high capacities and low costs is one the main challenges of hydrogen as a future alternative fuel. In this paper, a new hydrogen production system is designed and fabricated to investigate hydrogen production using aluminum and solar energy. Numerous experiments are performed to evaluate the hydrogen production rate, quantitatively and qualitatively. Moreover, correlations between the total hydrogen production volume over time and other parameters are developed and the energy efficiency and conversion ratio of the system are determined. Also, a method is developed to obtain an optimal and stable hydrogen production rate based on system scale and consumed materials. It is observed that at low temperatures, the hydrogen production volume, efficiency and COP of the system increase at a higher sodium hydroxide molarity. In contrast, at high temperatures the results are vice versa. The maximum hydrogen production volume, hydrogen production rate, reactor COP and system efficiency using 0.5 M NaOH solution containing 3.33 g lit^?1 aluminum at 30 °C are 6119 mL, 420 mL min^?1, 1261 mL H₂ per 1 g of Al, and 16%, respectively.