Hydrogen Sorption Studies Research Articles

Pd-H as an irreplaceable model system for the study of hydrogen electrosorption in aqueous and non-aqueous electrolytes

Even though Pd-H system has been known since the nineteenth century, it is still of interest to scientists. Pd thin film electrode (called as a Limited Volume Electrode – LVE) is able to electrosorb hydrogen form aqueous (acid, base) and non-aqueous electrolytes (e.g. ionic liquids). Therefore Pd-H is an irreplaceable model system for the study of hydrogen electrosorption in different media. The paper presents: (1) short overview of the study of hydrogen sorption in Pd, (2) the detailed description of the electrochemical measurement methods and (3) the equations for the determination of hydrogen electrosorption charges needed to hydrogen electrosorption isotherms creation. The presented approach can be applied for laboratory work. The results show that Pd-LVE can be effectively used as a model system before the studies of multicomponent hydrogen storage alloys (e.g. AB5 alloys).Graphical abstract

Hydrogen sorption studies of palladium decorated graphene nanoplatelets and carbon samples

With the increasing population of the world, the need for energy resources is increasing rapidly due to the development of the industry. 88% of the world's energy needs are met from fossil fuels. Since there is a decrease in fossil fuel reserves and the fact that these fuels cause environmental pollution, there is an increase in the number of studies aimed to develop alternative energy sources nowadays. Hydrogen is considered to be a very important alternative energy source due to its some specific properties such as being abundant in nature, high calorific value and producing only water as waste when burned. An important problem with the use of hydrogen as an energy source is its safe storage. Therefore, method development is extremely important for efficient and safe storage of hydrogen. Surface area, surface characteristics and pore size distribution are important parameters in determining the adsorption capacity, and it is needed to develop new adsorbents with optimum parameters providing high hydrogen adsorption capacity. Until recently, several porous adsorbents have been investigated extensively for hydrogen storage. In this study, it was aimed to develop and compare novel Pd/carbon, Pd/multiwalled carbon nanotube, and Pd/graphene composites for hydrogen sorption. All the palladium/carbon composites were characterized by t-plot, BJH desorption pore size distributions, N2 adsorption/desorption isotherms, and SEM techniques. The maximum hydrogen storage of 2.25 wt.% at −196 °C was achieved for Pd/KAC composite sample. It has been observed that the spillover effect of palladium increases the hydrogen sorption capacity.

Multi-functional palladium-ruthenium nanocomposites: an approach towards semi-hydrogenation catalysis and hydrogen sorption.

Development of heterogeneous metal catalysts with superior activity and high selectivity towards the semi-hydrogenation of alkynes is of significant industrial importance. Bimetallic Pd-Ru nanocomposites were synthesized over the entire composition range using a capping-agent assisted solution-based approach. The as-prepared nanocomposites demonstrated excellent catalytic activity towards the hydrogenation of a wide range of olefinic substrates and exceptional selectivity towards styrene in a phenylacetylene semi-hydrogenation reaction under mild conditions. In addition, hydrogen sorption studies were performed on the as-prepared bimetallic Pd-Ru nanomaterials, where an increase in the incorporation of Ru atoms into the bimetallic structure resulted in a decrease in the hydrogen storage capacity of the resulting material. Comprehensive structural characterization and insights obtained from the hydrogen sorption studies revealed that the presence of weakly bound hydrogen atoms in the hydride phase of the bimetallic species contributes to its excellent selectivity in hydrogenation reactions.

DFT study of hydrogen sorption on light metal (Li, Be, and Na) decorated novel fullerene-CNTs networks

Novel carbon-based periodic networks of crossed nanotubes with fullerene junctions (FNT-nets) has been designed as a potential solid hydrogen storage medium. Density functional theory calculations and molecular dynamics simulations have been performed to explore the structural stability and the hydrogen-storage potential of FNT-nets. Via the B-doping strategy, the binding energies of the alkali metal (Li, Na) and alkaline-earth metal (Be) were effectively improved to 2.47, 2.10, and 1.98 eV, respectively. The Li, Na, and Be atoms could be firmly dispersed atomically on the surface of B-FNT-nets, donating 0.732, 0.711, and 1.455 e to the substrate. The positive charge on the metal proved to be proportional to the strength of H2 polarization. Overall, up to four hydrogen molecules could be stored around one lithium with an average adsorption energy of 0.20 eV. Five hydrogen molecules were found to be around sodium and beryllium atoms with 0.17 and 0.27 eV in the range of reversible physical adsorption. The corresponding theoretical uptakes for Li@C158B22, Na@C132B24, and Be@C132B24 systems (13.95, 10.09, and 10.85 wt%, respectively) exceed the ultimate goal (6.5 wt%) as laid out by US Department of Energy. Our results reveal that the FNT-nets are good candidates for hydrogen storage.

DUT-5 modified Pd metal-nanoparticles: synthesis, chemical stability, and hydrogen sorption studies

The safety and effectiveness of hydrogen storage are important factors in supporting the utilization of hydrogen as fuel. One of the MOFs materials might be potentially used for hydrogen storage is MOF based on Al3+ including ([Al(OH)BPDC]) (BPDC: 4,4′-biphenyl dicarboxylic acid) which well known as Dresden University of Technology (DUT-5). This study aims to investigate the influence of Pd metal nanoparticles embedded into DUT-5 with a variation: 1 and 5 wt% toward the structural feature and hydrogen sorption properties. According to XRD and FTIR spectroscopy, nitrogen sorption isotherm and SEM-EDX analysis, the basic structure of DUT-5 were partially decomposed after the impregnation process. TEM analysis showed Pd nanoparticles were well dispersed into DUT-5. Nitrogen sorption isotherm revealed that Pd loading into DUT-5 lead to decrease surface area and pore volume of DUT-5 up to 85.82%. Based on thermogravimetry analysis, thermal stability of the material did not change after impregnation. Hydrogen sorption measurement revealed the presence of Pd is not able to increase hydrogen storage capacity of DUT-5 due to the framework destruction, however, in Pd/DUT-5 materials, the increasing of Pd concentration can increase the hydrogen storage capacity which might be due to a spillover effect.

Structural, Electrochemical and Hydrogen Sorption Studies of Nanocrystalline Ti-V-Co and Ti-V-Ni-Co Alloys Synthesized by Mechanical Alloying Method

In this paper, Ti-V-Co and Ti-V-Ni-Co alloys are considered as the hydrogen storage systems and the negative electrodes in Ni-MHx secondary batteries. This work shows results of studies that have been made on Ti0.5V1.5−xCox and Ti0.5V1.4−xNi0.1Cox nanocrystalline alloys (x = 0, 0.1 0.2, 0.3) synthesized by the mechanical alloying technique. The goal of this study is to determine an effect of partial replacement of V by Co atoms on hydrogen storage and electrochemical properties of Ti-V and Ti-V-Ni alloys. X-ray diffraction studies have proven that 14 h of the ball milling has resulted in crystallization of body-centered-cubic solid solution. Studies performed on high-resolution transmission electron microscope confirm creation of nanocrystalline materials. Hydrogen sorption/desorption measurements that have been performed at 303 K show that Co accelerates the hydrogen sorption process, diminishes hysteresis and ameliorates the hydrogen storage reversibility. Properties of Ti-V-Co alloys, described in this work, originate mainly from structure of these materials. Electrochemical measurements of Ti-V-Co alloys have shown these materials poorly absorb hydrogen in 6 M KOH solution. Ti0.5V1.4−xNi0.1Cox alloys are characterized by better activation properties and improved cyclability in comparison to Co-free Ti0.5V1.4Ni0.1 alloy.

The study of hydrogen sorption in palladium limited volume electrode from DEMA-TFO ionic liquid

Hydrogen sorption into palladium limited volume electrode (Pd-LVE) was studied in protic ionic liquid – diethylmethylammonium triflate (DEMA-TFO) using cyclic voltammetry (CV), chronopotentiometry (CP) and chronoamperometry (CA) at constant temperature (298 K). Pd-LVE was obtained potentiostatically from the aqueous solution of PdCl2. The results were compared with those obtained in aqueous 0.5 M H2SO4 solution. As the process of hydrogen sorption in ionic liquid medium is much less reversible than in acidic aqueous solution – the hydrogen pretreatment procedure (HPP) significantly increases the reversibility of this process at temperature of 298 K. The amount of absorbed hydrogen in DEMA-TFO is comparable with this in aqueous solution of acid and reaches the maximum value of H/Pd ca. 0.7. The hydrogen absorption isotherm was measured with the use of CV and CP techniques.

ORDERED NANOSTRUCTURED CARBONS, NCCR-41 AND CMK-3: SYNTHESIS, CHARACTERIZATION, AND HYDROGEN SORPTION STUDIES

ORDERED NANOSTRUCTURED CARBONS, NCCR-41 AND CMK-3: SYNTHESIS, CHARACTERIZATION, AND HYDROGEN SORPTION STUDIES

Theoretical study of hydrogen sorption on LaNi5 using statistical physics treatment: microscopic and macroscopic investigation

In the present work, experimental absorption isotherms of hydrogen in LaNi5 at three temperatures have been fitted using a monolayer model treated by statistical physics by means of the grand canonical ensemble. Six parameters of the model are fitted, namely two numbers of absorbed atoms per, site n1 and n2, two receptor site densities, N1M and N1M and two energetic parameters, P1 and P2. The behaviors of these parameters are discussed in relationship with absorption process. Starting from the monolayer model, we determined the absorption energies which are typically ranged between 85 and 101 kJ/mol comparable to usual chemical bond energies. Calculated thermodynamic potentials such as internal energy (Eint) and Gibbs free energy (G) suggested that the absorption processes was exothermic and spontaneous.

In situ X-Ray diffraction study of hydrogen sorption in V-rich Ti–V–Cr bcc solid solutions

Alloying of vanadium with a combination of titanium and chromium has been investigated in this study. Hydrogenation/desorption of several alloys under similar experimental conditions has been performed and sequentially followed by means of in situ X-Ray powder diffraction. This latter technique has been used as a probe of formation or decomposition of hydrides. Geometrical effects are discussed and account for the observed similarities of the sorption properties.

Hydrogen sorption hysteresis and superior storage capacity of silicon-carbide nanotubes over their carbon counterparts

We report for the first time the results of an extensive experimental study of hydrogen sorption in silicon-carbide nanotubes (SiCNTs), which were synthesized using the reaction between SiO vapor and carbon nanotubes (CNTs) in an argon atmosphere in the temperature range 1200 °C–1500 °C. The as-synthesized SiCNTs were then purified using a sodium hydroxide solution in order to remove the side products of the synthesis reaction. The hydrogen sorption characteristics of the as-synthesized SiCNTs, as well as those of the purified SiCNTs were then measured at 25 °C and for pressures of up to 100 bars. The results reveal hysteresis between the adsorption and desorption isotherms, which we attribute to the presence of metal impurities and/or the multilayer structure of the nanotubes. The hydrogen storage capacity of the as-synthesized SiCNTs is similar to that of the CNTs, whereas for the purified SiCNTs it is 50% higher than that of the CNTs, in agreement with the results of molecular simulations reported previously. In addition, the hydrogen uptake rate in the SiCNTs is about five times faster than that in the CNTs and, in contrast with the CNTs, its desorption from SiCNTs is completely reversible under vacuum.

Study of Hydrogen Sorption and Desorption by Cast and Rapidly Quenched ZR–V Alloys

We study the processes of hydrogen absorption and desorption by Zr–V alloys of different compositions in the as-cast state and in the state obtained after rapid quenching from the melt. It is shown that the characteristics of sorption-desorption of cast alloys are better than the corresponding of rapidly quenched alloys.

Synthesis, characterization and hydrogen sorption studies of mixed sodium‐potassium alanate

AbstractThe aim of the present investigation is to synthesize mixed sodium potassium alanate (K2NaAlH6) and to explore its hydrogen sorption characteristics. K2NaAlH6 is synthesized through ball milling of KH and NaAlH4 in the molar ratio 2:1 under hydrogen pressure of 10 bar. The temperature programmed desorption experiment shows that the synthesized K2NaAlH6 has peak desorption temperature of ∼352°C and reveals appreciable rehydrogenation kinetics under 6 bar hydrogen pressure at 300°C. The investigations are also focused on the catalytic effect of carbon nanostructures (CNS) namely, the graphene sheet (GS) and single wall carbon nanotube (SWCNT) and titanium halides (TiCl3 and TiF3) on K2NaAlH6. In the case of graphene and SWCNT catalyzed K2NaAlH6, the peak desorption temperature gets reduced to ∼347°C and ∼341°C respectively. The catalytic effects of CNS and titanium halide on K2NaAlH6 are also compared in the investigation. Between the two types of catalysts, halides are found to be better than CNS and out of the two halides, TiF3 is found to be the best catalyst for hydrogen sorption in K2NaAlH6. The peak desorption temperature decreases significantly from 352°C to ∼324°C for TiF3 catalyzed K2NaAlH6. Thus, the desorption activation energy reduces drastically from 124.43 kJ/mol (synthesized K2NaAlH6) to 88.05 kJ/mol for TiF3 catalyzed K2NaAlH6.

High pressure DSC study of hydrogen sorption in MgH 2/graphite mixtures: Effects of sintering and oxidation

Hydrogen absorption and desorption properties of ball milled Mg and Mg/graphite materials were analyzed by high pressure differential scanning calorimetry. The influence on hydrogen sorption kinetics of different graphite distribution, oxygen poisoning and magnesium sintering was studied. The Mg/graphite mixture with graphite distributed in the bulk showed better kinetics than the material with graphite located on the surface and Mg without additive. The effect of sintering and oxygen poisoning was a progressive storage capacity loss, due to a kinetic limitation in the case of sintering, and due to irreversible magnesium oxidation in the case of poisoning. The mixtures with graphite exhibited more resistance toward oxygen contamination, particularly in the case where graphite was primarily located on the surface compared to the material with graphite well dispersed in the bulk.

Hydrogen sorption in transition metal modified mesoporous materials

Ni, Rh and Pd incorporated mesoporous MCM-41, MCM-48, HMS and SBA-15 samples were synthesized and were characterized using XRD, ICP/EDX and N 2 adsorption–desorption at 77.4 K. The hydrogen adsorption studies in the synthesized materials were performed at 77.4 K (up to 112 kPa) and 303 K (up to 4000 kPa). The hydrogen adsorption isotherms of pristine and transition metals incorporated mesoporous materials at 77.4 K were completely reversible reflecting physisorption of hydrogen in these materials. The hydrogen adsorption isotherms at 303 K were not reversible showing the chemisorption of hydrogen in these materials at 303 K. Hydrogen sorption studies showed that transition metal modification improved the hydrogen storage capacity of mesoporous materials at 303 K. The desorption of the adsorbed hydrogen by heating up to 500 K from the mesoporous materials were also carried out for studying the recovery of adsorbed hydrogen from transition metal incorporated mesoporous materials.

Porous Metal-Organic Frameworks Based on an Anthracene Derivative: Syntheses, Structure Analysis, and Hydrogen Sorption Studies

Solvothermal assembly of 5,5'-(9,10-anthracenediyl)di-isophthalate (H(4)adip) with in situ-generated dicopper and diiron paddlewheel secondary building units (SBUs) afforded two porous metal-organic frameworks (MOFs), designated as PCN-14 and PCN-15, respectively. The two MOFs crystallize in different structures, characterized by a difference in the dihedral angles between the anthracene and the phenyl rings of the adip ligand. PCN-14 retains permanent porosity under dehydration and contains nanoscopic cages while PCN-15 contains only one-dimensional hexagonal channels along the (0 0 1) direction which require solvent stabilization. The aromaticity of the anthracene rings of the adip ligand in conjunction with the nanoscopic cages grants PCN-14 high excess hydrogen adsorption capacity of 2.70 wt % at 77 K, 760 Torr (4.42 wt % at saturation), as well as high hydrogen affinity of 8.6 kJ/mol at low H(2) coverage. These values are compared to other tetracarboxylate-derived MOFs to better understand the role of the aromatic rings in hydrogen adsorption.

Further Investigation of the Effect of Framework Catenation on Hydrogen Uptake in Metal−Organic Frameworks

Hydrogen-sorption studies have been carried out for the catenation isomer pairs of PCN-6 and PCN-6' (both have the formula of Cu(3)(TATB)(2), where TATB represents 4,4',4''-s-triazine-2,4,6-triyl-tribenzoate with a formula of C(24)H(12)N(3)O(6)). Inelastic neutron scattering (INS) studies reveal that the initial sites occupied by adsorbed H(2) are the open Cu centers of the paddlewheel units with comparable interaction energies in the two isomers. At high H(2) loadings, where the H(2) molecules adsorb mainly on or around the organic linkers, the interaction is found to be substantially stronger in catenated PCN-6 than in noncatenated PCN-6', leading to much higher H(2) uptake in the isomer with catenation. Hydrogen sorption measurements at pressures up to 50 bar demonstrate that framework catenation can be favorable for the enhancement of hydrogen adsorption. For example, the excess hydrogen uptake of PCN-6 is 72 mg/g (6.7 wt %) at 77 K/50 bar or 9.3 mg/g (0.92 wt %) at 298 K/50 bar, respectively, and that for PCN-6' is 42 mg/g (4.0 wt %) at 77 K/50 bar or 4.0 mg/g (0.40 wt %) at 298 K/50 bar. Importantly, PCN-6 exhibits a total hydrogen uptake of 95 mg/g (8.7 wt %) (corresponding to a total volumetric value of 53.0 g/L, estimated based on crystallographic density) at 77 K/50 bar and 15 mg/g (1.5 wt %) at 298 K/50 bar. Significantly, the expected usable capacity of PCN-6 is as high as 75 mg/g (or 41.9 g/L) at 77 K, if a recharging pressure of 1.5 bar is assumed.

Performance of air cooled hydrogen storage device with external fins

Minimization of total weight is the major criterion in the design of a solid state hydrogen storage device for mobile or portable applications. The design should also address the requirements such as storage capacity, charge/discharge rates, space constraints, coolant temperature and hydrogen supply pressure. To achieve this, one should be able to reliably predict the dynamic performance of the storage device. In this paper, a parametric study of hydrogen sorption in an air-cooled annular cylindrical hydrogen storage device with external fins is reported. LaNi 5 , which has excellent hydrogen storage properties is used as the hydriding material. The influence of different geometric parameters such as hydride bed thickness and fin height, and operational parameters such as hydrogen supply pressure and cooling air temperature are studied. Copyright , Manchester University Press.

Preparation of activated carbons from Zonguldak region coals by physical and chemical activations for hydrogen sorption

Activated carbons were prepared by physical and chemical activations from coals collected from two mines (Kilimli and Armutcuk) in Zonguldak region, Turkey under different conditions. Ash content was reduced considerably by use of HCl and HF treatments. Pyrolytic thermal treatments in a temperature range of 600– 900 ∘ C under N 2 flow and chemical treatments using different chemical agents such as KOH, NH 4Cl, ZnCl 2 were applied to the coal samples from the two mines. N 2 adsorption isotherms were obtained at 77.4 K for the thermally and the chemically treated samples and the data were used for the evaluation of the specific surface area, total pore volumes and the average pore sizes of the samples. Higher surface area values were obtained from Kilimli coal samples than Armutcuk. The BET surface area of the Kilimli coal samples which were initially have a value of 1.20 m 2/g were increased to 52.62 m 2/g after pyrolytic heat treatments at 800 ∘ C and increased to a value of 830.5 m 2/g by treating the coals with KOH + NH 4 Cl mixture at 750 ∘ C followed by oxidation of the samples mixed with ZnCl 2. The activated carbon samples were prepared for the purpose of their evaluation in hydrogen sorption studies.

Synthesis, Structure Determination, and Hydrogen Sorption Studies of New Metal−Organic Frameworks Using Triazole and Naphthalenedicarboxylic Acid

Two new metal−organic framework compounds were synthesized under solvothermal conditions using Zn2+ ion, 1,2,4-triazole (TRZ), and 1,4- and 2,6-naphthalenedicarboxylic acids (NDC): Zn4(TRZ)4(1,4-NDC)2·2DMF·2H2O (1) and Zn4(TRZ)4(2,6-NDC)2·2DMF·4H2O (2). Their crystal structures were characterized by single-crystal X-ray diffraction. Structure 1 crystallizes in the P21/n space group with a = 13.609(2) Å, b = 27.181(5) Å, c = 13.617(3) Å, β = 92.46(1) °, V = 5032.4(16) Å3, and Z = 4. Structure 2 crystallizes in orthorhombic Pna21 space group with a = 30.978(6) Å, b = 12.620(3) Å, c = 13.339(3) Å, V = 5215(2) Å3, and Z = 4. Both structures are analogues of the previously reported Zn4(TRZ)4(1,4-BDC)2·16H2O where the layers of Zn−triazole moieties are pillared by aromatic dicarboxylates to create 3-D open frameworks. Nitrogen sorption studies revealed that these structures have Brunaer−Emmett−Teller (BET) surface areas of 362.1−584.1 m2/g. Hydrogen sorption experiments showed they can store 0.84−1.09 wt % of H2 at 77 K and 1 atm. Although they do not contain large pores or surface areas, they possess the hydrogen sorption capacities comparable to those of highly porous metal−organic frameworks.