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The efficient operation of a metal hydride reactor depends on the hydrogen sorption and desorption reaction rate. In this regard, special attention is paid to heat management solutions when designing metal hydride hydrogen storage systems. One of the effective solutions for improving the heat and mass transfer effect in metal hydride beds is the use of heat exchangers. The design of modern cylindrical-shaped reactors makes it possible to optimize the number of heat exchange elements, design of fins and cooling tubes, filter arrangement and geometrical distribution of metal hydride bed elements. Thus, the development of a metal hydride reactor design with optimal weight and size characteristics, taking into account the efficiency of heat transfer and metal hydride bed design, is the relevant task. This paper discusses the influence of different configurations of heat exchangers and metal hydride bed for modern solid-state hydrogen storage systems. The main advantages and disadvantages of various configurations are considered in terms of heat transfer as well as weight and size characteristics. A comparative analysis of the heat exchangers, fins and other solutions efficiency has been performed, which makes it possible to summarize and facilitate the choice of the reactor configuration in the future.

Minimizing e-waste by extracting valuable parts or by utilizing them for the development of devices can be a productive way to manage it. The present research work focusses on the use of electrochemically modified steel mesh (SM) extracted from discarded nickel-metal hydride (Ni-MH) batteries for the application of energy generation. Upon deposition of amorphous nickel selenide film on SM, significant activity towards catalysing the urea oxidation reaction (UOR) is reported. Electrodeposition of Nickel selenide on SM was confirmed by analytical techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and EDX studies. Electrochemical studies reveal that for NiSe@SM a potential of 1.375 V vs RHE is needed to obtain a current density of 10 mA cm −2 , which is significantly higher than the noble metal-based mixed metal oxide (MMO) catalyst. Further, the NiSe@SM showed minimum Tafel slope of 47 mV dec −1 and exhibited minimum charge transfer resistance among all the tested films. Furthermore, the film showed stability of 9 h confirming the robustness of catalyst. The findings indicate that the inclusion of Selenium led to an improvement in the activity and kinetics of the UOR. This research lays the groundwork for developing environmentally acceptable electrode materials from electronic waste for generating sustainable energy. Graphical abstract

Metal hydrides are an interesting group of chemical compounds, able to store hydrogen in a reversible, compact and safe manner. Among them, A2B7-type intermetallic alloys based on La-Mg-Ni have attracted particular attention due to their high electrochemical hydrogen storage capacity (∼400 mAh/g) and extended cycle life. However, the presence of Mg makes their synthesis via conventional metallurgical routes challenging. Replacing Mg with Y is a viable approach. Herein, we present a systematic study for a series of compounds with a nominal composition of La2-xYxNi6.50Mn0.33Al0.17, x = 0.33, 0.67, 1.00, 1.33, 1.67, focusing on the relationship between the material structural properties and hydrogen sorption performances. The results show that while the hydrogen-induced phase amorphization occurs in the Y-poor samples (x < 1.00) already during the first hydrogen absorption, a higher Y content helps to maintain the material crystallinity during the hydrogenation cycles and increases its H-storage capacity (1.37 wt.% for x = 1.00 vs. 1.60 wt.% for x = 1.67 at 50 °C). Thermal conductivity experiments on the studied compositions indicate the importance of thermal transfer between powder individual particles and/or a measuring instrument.

Highlights Hydrogen storage performance of V-Ti-based solid solution alloys is related to the elementary composition, phase structure, and homogeneity. Micro-strain accumulation is responsible for capacity degradation. Low-cost and high-performance V-Ti-based solid solution alloys with high reversible hydrogen storage capacity, good cyclic durability, and excellent activation performance should be developed. This review details the advancement in the development of V–Ti-based hydrogen storage materials for using in metal hydride (MH) tanks to supply hydrogen to fuel cells at relatively ambient temperatures and pressures. V–Ti-based solid solution alloys are excellent hydrogen storage materials among many metal hydrides due to their high reversible hydrogen storage capacity which is over 2 wt% at ambient temperature. The preparation methods, structure characteristics, improvement methods of hydrogen storage performance, and attenuation mechanism are systematically summarized and discussed. The relationships between hydrogen storage properties and alloy compositions as well as phase structures are discussed emphatically. For large-scale applications on MH tanks, it is necessary to develop low-cost and high-performance V–Ti-based solid solution alloys with high reversible hydrogen storage capacity, good cyclic durability, and excellent activation performance.

There is still much to be learned about the properties of siderophores and their applications. This study was designed to characterize and optimize the production of the siderophore produced by a marine bacterium Pseudomonas sp. strain ASA235 and then evaluate their use in bioleaching of rare earth elements (REEs) from spent Nickel–metal hydride (NiMH) batteries. The results of both Tetrazolium and Arnowʼs tests indicated that the test organism produces a mixed-type siderophore of pyoverdine family, a result that was confirmed by FT-IR and MALDI-TOFF analyses. Optimization of pH, temperature, incubation period, and iron concentration for siderophore production led to a noticeable shift from 44.5% up to 91% siderophore unit when the test bacterium was incubated at 28 °C and pH 7 after 72 h in the absence of iron. The purified siderophore showed the ability to bleach about 14.8% of lanthanum from the anode of the NiMH battery along with other elements, although in lower amounts. This data put siderophores in distinct focus for further prospective studies intending the bioleaching of such precious elements. The scaling up of this process and optimization would make a big difference in such a green bioleaching strategy, allowing us to recover such precious elements in an environmentally friendly way.

Considering how important rare earth elements (REEs) are for many different industries, it is important to separate them from other elements. An extractant that binds to REEs inexpensively and selectively even in the presence of interfering ions can be used to develop a useful separation method. This work was designed to recover REEs from spent nickel–metal hydride batteries using ammonium sulfate. The chemical composition of the Ni–MH batteries was examined. The operating leaching conditions of REE extraction from black powder were experimentally optimized. The optimal conditions for the dissolution of approximately 99.98% of REEs and almost all zinc were attained through use of a 300 g/L (NH4)2SO4 concentration after 180 min of leaching time and a 1:3 solid/liquid phase ratio at 120 °C. The kinetic data fit the chemical control model. The separation of total REEs and zinc was conducted under traditional conditions to produce both metal values in marketable forms. The work then shifted to separate cerium as an individual REE through acid baking with HCl, thus leaving pure cerium behind.

Hirshfeld atom refinement (HAR) is a method which enables the user to obtain more accurate positions of hydrogen atoms bonded to light chemical elements using X-ray data. When data quality permits, this method can be extended to hydrogen-bonded transition metals (TMs), as in hydride complexes. However, addressing hydrogen thermal motions with HAR, particularly in TM hydrides, presents a challenge. At the same time, proper description of thermal vibrations can be vital for determining hydrogen positions correctly. In this study, we employ tools such as SHADE3 and Normal Mode Refinement (NoMoRe) to estimate anisotropic displacement parameters (ADPs) for hydrogen atoms during HAR and IAM refinements performed for seven structures of TM (Fe, Ni, Cr, Nb, Rh and Os) and metalloid (Sb) hydride complexes for which both the neutron and the X-ray structures have been determined. A direct comparison between neutron and HAR/SHADE3/NoMoRe ADPs reveals that the similarity between neutron hydrogen ADPs and those estimated with NoMoRe or SHADE3 is significantly higher than when hydrogen ADPs are refined with HAR. Regarding TM—H bond lengths, traditional HAR exhibits a slight advantage over the other methods. However, combining NoMoRe/SHADE3 with HAR results in a minor decrease in agreement with neutron TM—H bond lengths. For the Cr complex, for which high-resolution X-ray data were collected, an investigation of resolution-related effects was possible.

Current AB 5 -type hydrogen storage alloys employed in nickel-metal hydride (NiMH) batteries exhibit exceptional low-temperature discharge performance but suffer from limited cycle life and insufficient high-temperature stability. To overcome these challenges, we introduce a hydrothermal synthesized LaF 3 coating layer on the surface of the AB 5 anode material. This LaF 3 coating layer adds a protective barrier for the active material, significantly improving the battery’s cycle life and high-temperature stability. Our findings indicate that (1) the LaF 3 coated anode demonstrates an extended cycle life with increased specific capacity and a capacity retention of 88% after 40 cycles of abusive overcharging and rapid discharging at room temperature. (2) The synthesized anode exhibits a 97% recovery of its specific capacity of 292.7 mAh/g following 144 h of high-temperature storage. (3) The low-temperature discharge capacity of the synthesized anode remains on par with the pristine AB 5 alloy at 230.4 mAh/g in a −40 °C environment. This research presents a significant advancement in hydrogen storage alloy coatings and offers valuable insights for designing electrodes in NiMH batteries.

Back-scattered electron imaging and X-ray elemental mapping were combined in a tabletop scanning electron microscope (SEM) to investigate cross-sections of three AA-type (mignon) nickel–metal hydride (NiMH) batteries from different manufacturers. All batteries underwent 500–800 charge/discharge cycles and reached their end of lifetime after several years as they could no longer hold any significant electric charge (less than 20% of nominal charge capacity), but none showed any short-circuiting. The types of degradation observed in this field study included electrode swelling, metallic nickel formation and carbon incorporation into pores in the positive electrodes and, in the negative electrodes, metal alloy segregation of different elements such as nickel, lanthanum and, in one case, sodium, as well as grain break-up and pore formation. All these phenomena could readily be observed at rather small magnifications. This will be important for the improvement of NiMH batteries, for which new generations with nominally slightly increased charge capacities are being marketed all the time.

Nanoscaling interstitial metal hydrides offers opportunities for hydrogenation applications by enhancing kinetics, increasing surface area, and allowing for tunable properties. The introduction of interfaces impacts hydrogen absorption properties and distribution heterogeneously, making it, however, challenging to examine the multiple concurrent mechanisms, especially at the atomic level. Here, the effect of proximity on interstitial hydrogen in ultrathin single‐crystalline vanadium films is demonstrated by comparing hydride formation in identically strained Fe/V‐ and Cr/V‐superlattices. Pressure concentration and excess resistivity isotherms show higher absolute solubility of hydrogen, higher critical temperature, and concentration in a Cr/V‐superlattice. Direct measurements of hydrogen site location and thermal vibrations show identical site occupation of octahedral z at room temperature with a vibrational amplitude of 0.20–0.25 Å over a wide range of hydrogen concentrations. These findings are consistent with a more extended region of hydrogen depletion in the vicinity of Fe compared to Cr, which showcases an inverse of the hydrogen spillover effect. Advancing the understanding of interface effects resolves previously puzzling differences in the hydrogen loading of Fe/V‐ and Cr/V‐superlattices and is relevant for advancing both catalysis and storage. Interstitial hydrogen behaves distinctly at interfaces compared to the bulk. Vanadium films show proximity‐dependent hydrogen depletion near interfaces–an inverse of hydrogen spillover. Ion beam and resistivity measurements reveal Fe/V‐superlattices have lower hydrogen solubility and higher critical temperature than Cr/V due to proximity‐induced finite size effects, with similar site occupation.