Good Hydrogen Storage Capacity Research Articles

Laser-assisted synthesis of bentonite/Pd nanocomposite and its electrochemical hydrogen storage capacity

Today, the increasing world population has led to increased consumption of fossil fuels for energy production, causing environmental problems. Hydrogen with high energy density can be used as a suitable alternative to fossil fuel sources. Hydrogen atoms can be stored on porous structures by physical interaction. Hence, simple and eco-friendly approaches have been taken to prepare bentonite/Pd nanocomposites for electrochemical hydrogen storage. Laser ablation in the deionized water medium was employed as a physical route for the synthesis of Pd nanoparticles (NPs). Bentonite, a porous substrate with a high surface area of 47 m2/g, was employed for the deposition of Pd NPs via physical mixing. The morphological study of nanocomposite indicated that the spherically shaped Pd NPs with a diameter of 20–27 nm are successfully deposited on the bentonite substrate. The as-prepared nanocomposites were loaded on stainless steel electrode through drop-casting and their hydrogen storage capacity was determined via cyclic voltammetry (CV). The CV measurement of the B/Pdx electrodes (x is laser ablation times of 15, 30, 45, and 60 min) in 1.0 M KOH electrolyte at the scan rate of 100 mV/s at room temperature demonstrated good hydrogen storage capacity (37 C/g) and stability during 200 scans.

Hydrogen storage properties of new A3B2-type TiZrNbCrFe high-entropy alloy

Crystal structure and hydrogen storage properties of a novel equiatomic TiZrNbCrFe high-entropy alloy (HEA) were studied. The selected alloy, which had a A3B2-type configuration (A: elements forming hydride, B: elements with low chemical affinity with hydrogen) was designed to produce a hydride with a hydrogen-to-metal atomic ratio (H/M) higher than those for the AB2- and AB-type alloys. The phase stability of alloy was investigated through thermodynamic calculations by the CALPHAD method. The alloy after arc melting showed the dominant presence of a solid solution C14 Laves phase (98.4%) with a minor proportion of a disordered BCC phase (1.6%). Hydrogen storage properties investigated at different temperatures revealed that the alloy was able to reversibly absorb and fully desorb 1.9 wt% of hydrogen at 473 K. During the hydrogenation, the initial C14 and BCC crystal structures were fully converted into the C14 and FCC hydrides, respectively. The H/M value was 1.32 which is higher than the value of 1 reported for the AB2- and AB-type HEAs. The present results show that good hydrogen storage capacity and reversibility at moderate temperatures can be attained in HEAs with new configurations such as A3B2/A3B2H7.

MgScH15: A highly stable cluster for hydrogen storage

Mg-Sc-H systems exhibit superior stability and high hydrogen storage capacity among the large class of magnesium-based hydrogen storage materials, but the underlying mechanisms for their outstanding hydrogen storage properties remain largely unexplored and require further investigation. Here, we have performed a comprehensive investigation on the structural evolution of MgScHn (n = 10–20) clusters by unbiased Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method combined with density functional theory (DFT) optimizations at the B3PW91/6-311 + G(d) level. Our results show that the MgScH15 cluster with Cs symmetry is found to be the most stable cluster with good hydrogen storage capacity of 17.8 wt% due to the strong interaction among the 1s orbitals of the H atoms, the 2p orbitals of the Mg atom and the 3d orbitals of the Sc atom. The present findings are promising for further exploring novel hydrogen storage nanomaterials.

Hybrid hollow structures for hydrogen storage

Nanohybrids have shown considerable promise for hydrogen storage due to their enhanced capacity and fast kinetics. Hollow nanostructures have attracted considerable attention in diverse contexts and recently have been envisaged as nanocontainers for hydrogen storage. In the current work a two-scale novel hollow nanohybrid is synthesized, wherein the outer Ni ‘capsule’ plays a catalytic role in the breakdown of hydrogen molecule into atomic form and the inner Mg hollow structure enhances the hydrogen storage via a multi-mode storage philosophy developed recently. The structure of the dual-phase nanohybrid is elucidated using transmission electron microscopy and selected area diffraction patterns and characterized for hydrogen storage via pressure-composition-isotherms. The system shows good hydrogen storage capacity (∼5 wt% at 10 bar & 180 °C); coupled with fast kinetics. The hydrogen is stored in an additional form than that reported earlier (interstitial compound).

Thermal decomposition synthesis, characterization and electrochemical hydrogen storage characteristics of Co3O4–CeO2 porous nanocomposite

Particle-like Co3O4–CeO2 nanocomposite was synthesized via a facile thermal decomposition process in the presence of fructose as a green capping agent and ammonium cerium(IV) nitrate as Ce source. The effect of various parameters such as different cobalt sources, calcination temperature and time were investigated on the size and morphology of products. The transmission electron microscopy observations indicated that the synthesized products have a particle-like shape with an average diameter of 18–35 nm. For the first time, the electrochemical hydrogen storage performance of Co3O4–CeO2 porous nanocomposite was investigated via chronopotentiometry method in aqueous KOH solution in this paper. The electrochemical measurements showed that this product has a good hydrogen storage capacity at room temperature. Its maximum discharge capacity was 5200 mAh/g after 20 cycles. Therefore, Co3O4–CeO2 porous nanocomposite showed that it is a good candidate for electrochemical hydrogen storage.

Synthesis of N-S Doped Graphene for Hydrogen Storage

Doping is a common and effective approach to tailor semiconductor properties. Theoretical studies predicted that doping graphene with nitrogen and sulphur can tailor its electronic properties and chemical reactivity. Hydrogen as an environment friendly fuel is a strong contender for fossil fuel based auto fuel. But the major stumbling block in realizing this is the risk involved in transporting hydrogen due to the risk of fire hazard owing to wider limits of in flammability. Hence, it is important to develop efficient hydrogen storage devices for storing and transporting hydrogen safely. Graphene in its original form do not have good hydrogen storage capacity but synthesized graphene are reported to be the best method for hydrogen storage since (Nitrogen–sulphur) doped graphene exhibit good electrical conductivity, long durability and high selectivity. CVD (Chemical vapour deposition)method is also considered one of the best method for synthesis of grapheme.

Development of High Storage Capacity Complex Hydrides for Reversible Hydrogen Storage

In this study, novel light weight complex hydrides for reversible hydrogen storage are developed and synthesized. Metal hydrides are generally known to have a good hydrogen storage capacity but possess slow kinetics, irreversibility and high activation energy barriers. Therefore, metal hydrides often require very high temperature (>350° C) to release hydrogen. This behavior makes their wide usage in hydrogen storage applications difficult. We have extensively employed a unique synthesis approach of solid state mechano-chemical process, via high energy ball milling. From this synthesis process, eight new complex hydrides have been prepared and each of them are characterized using high pressure Sievert's type volumetric apparatus, residual gas or mass spectrometric analysis (RGA/MS), and the Fourier transform infrared spectroscopy (FT-IR) to determine their chemical and hydrogen sorption properties. The as-synthesized new complex hydrides with light weight elements such as lithium, magnesium, boron, aluminum etc. have demonstrated excellent physical and chemical behavior in terms of lower activation energies, higher reversible hydrogen storage capacity (i.e., ≥6wt%) at operating temperatures below 350° C, and faster reaction kinetics than their conventional metal hydride counterparts. Unfortunately, the residual gas analysis of these materials have revealed the evolution of some undesirable and toxic gases such as ammonia (NH3) and di-borane (B2H6) in addition to the release of hydrogen. The release of these toxic gases was eventually suppressed by catalysts added and destabilization proce- dures are mentioned explicitly. Among the various complex hydrides developed, two novel systems namely, Li-nMg-B-N-H and BNH6-nMgH2 have shown distinguishing properties as efficient reversible hydrogen storage materials.

Preparation and characterization of triptycene-based microporous poly(benzimidazole) networks

We demonstrate the synthesis of two triptycene-based microporous poly(benzimidazole) networks through condensation of triptycene-hexone with dialdehyde in refluxing glacial acetic acid containing ammonium acetate. The benzimidazole-linkage in the resulting polymers is confirmed by Fourier transform infrared and solid-state 13C CP/MAS NMR spectroscopy. The spindle-shaped morphology of the obtained polymers was also observed through scanning electron microscopy. The materials, with Brunauer–Emmet–Teller (BET) specific surface area over 600 m2 g−1, possess a good hydrogen storage capacity (up to 1.57 wt% at 77 K and 1.0 bar) and a high carbon dioxide uptake (up to 14.0 wt% at 273 K and 1.0 bar). These excellent performances would probably make them promising candidates for gas-selective adsorption, heterogeneous catalysis, and proton-exchange membrane fuel cells.

Chemical engineering of prehydrogenated C and BN-sheets by Li: Application in hydrogen storage

Our first-principles calculations show that if the hydrogen atoms on one of the faces of a graphane sheet (prehydrogenated graphene) are substituted with Li atoms, the resulting monolayer attains a good hydrogen storage capacity of around 3.8 wt % close to the revised Department of Energy (DOE) target. It is observed that Li atoms are strongly hybridized with the monolayer and donate their electrons to the substrate such that their binding energy to the surface becomes around −3.27 eV, which is far larger than the cohesive energy of Li in its metal bulk structure. It indicates that Li atoms on the monolayer are not aggregated or clusterized at high doping concentration and high temperature. Our calculation shows that the binding energy of H2 molecules with the monolayer surface is around −0.1 eV resulting from the electrostatic interaction of the polarized charge of hydrogen molecules with the induced electric field by positively charged Li atoms. Similarly, we have examined the hydrogen storage capacity of Li-substituted prehydrogenated boron nitride (BN) sheet; it is observed that it also has a very good hydrogen storage capability similar to Li-substituted graphane sheet.

Hydrogen absorption characteristics and electrochemical properties of Ti substituted Zr-based AB 2 alloys

The hydrogen absorption characteristics of Zr 1− x Ti x CrNi alloys, with x ranging between 0.1 and 0.4, were studied by volumetric and electrochemical techniques in order to determine their possible application as the negative electrode in nickel/metal–hydride rechargeable batteries. Electrodes of alloy powders mixed with different compacting additives were tested with respect to charge and discharge cycles in KOH solution. The effects of the electrode-compacting additive, discharge rate and temperature on the electrode discharge capacity were also investigated. The results obtained show that: (i) at 80°C the equilibrium pressures of Zr 1− x Ti x CrNi alloys with x=0.1 are 2.6 times higher than those for the unsubstituted ZrCrNi alloy, while maintaining a good hydrogen storage capacity; (ii) the Zr 0.9Ti 0.1CrNi alloy electrodes exhibit the highest discharge capacities and the best performances during fast charge–discharge cycling; (iii) the Ti substituted alloy electrodes using copper powder as compacting material show faster activation, while carbon–Teflon compacted electrodes exhibit the best cycle life behavior; (iv) for all Ti substituted alloy electrodes the discharge capacities increase with temperature.

Synthesis of Nanocrystalline CaNi<sub>5</sub>-Based Alloys and Use for Metal Hydride Electrode

The CaNi 5 -based alloys were synthesized by mechanical alloying followed by a low temperature annealing. Study shows that both substitution and annealing treatment affect the hydrogen storage capacity. Mm substitution for Ca results in an increased plateau pressure. The Zn and Al substitution for Ni leads to a bigger unit cell volume, a lower plateau pressure and a reduced capacity. Annealing treatment of the mechanically alloyed CaNi 5 -based alloys is a necessary process for obtaining good hydrogen storage capacity. The synthesized Ca-Mm-Ni-Zn-Al multicomponent nanocrystalline alloys exhibit fast kinetics on gas phase and electrochemical reaction and significantly improved cycle stability on electrochemical reaction.

Crystal structure and protium absorption properties of La-rich La(Ni, M) (x=3–4.7) (M=Al, Co, Mn, Si) melt-spun ribbons

Abstract The present study describes the rapid quenching effects on the solid-solution range of La(Ni, M) x ( x =3–4.7) (M=Al, Co, Mn, Si) alloys prepared by melt-spinning and discusses their protium (hydrogen atom) absorption properties. It is found that the single phase with CaCu 5 crystal structure extends to LaNi 4.65 compositional alloys. When x in LaNi 5− x becomes smaller, the alloy acquires better protium absorption properties including easier activation, better flatness of plateau region and a good hydrogen storage capacity comparable to those of LaNi 5 homogenized sample. On adopting a melt-spinning technique it is easy to form single phase of CaCu 5 type-structure for La-rich non-stoichiometric La–Ni–M alloys such as La(Ni, M) x ( x =3–4.7) (M=Al, Mn, Si) alloys. The readiness of forming a single phase CaCu 5 type-structure in melt-spun La–Ni–M alloys is in order of Al≥Si>Mn>Co.The phases formed and protium absorption properties of La-rich LaNi 4.5 M 0.2 melt-spun alloys are studied. It was found that LaNi 4.5 M 0.2 alloys had better protium absorption properties such as easier activation than the LaNi 4.65 binary alloy and as good hydrogen storage capacity as that of homogenized LaNi 5 .