Rare-earth Hydrogen Storage Research Articles

Carbon coating with different carbon sources on rare earth hydrogen storage alloy

The rare earth hydrogen storage alloy was coated with the same contents of carbon particles using sucrose, glucose, pitch, and chitosan as carbon sources, and compared with the samples of uncoated and mechanically mixed with the carbon powder. The results show that the maximum discharge capacity (Cmax), high-rate dischargeabilitiy (HRD), and cyclic stability after 500 cycles (S500) are improved to various degrees by carbon coating. It is found that the better the fluidity of carbon source in the carbonization process, the more uniform the carbon distributed on the alloy surface, and the longer the cyclic life of the alloy electrode. The less impurity remained after carbonization and the higher degree of graphitization of carbon, the better the electrocatalytic activity and HRD performance of the alloy electrode. The alloy coated with carbon particles using sucrose as carbon source has the best electrochemical properties. Compared with the uncoated sample, the Cmax of the alloy electrode increases from 354.5 to 359.0 mAh/g, the HRD1200 increases from 65.84% to 74.39%, and the S500 increases from 63.14% to 69.63%.

Excellent catalytic effect of LaNi5 on hydrogen storage properties for aluminium hydride at mild temperature

The catalytic effect of rare-earth hydrogen storage alloy is investigated for dehydrogenation of alane, which shows a significantly reduced onset dehydrogenation temperature (86 °C) with a high-purity hydrogen storage capacity of 8.6 wt% and an improved dehydrogenation kinetics property (6.3 wt% of dehydrogenation at 100 °C within 60 min). The related mechanism is that the catalytic sites on the surface of the hydrogen storage alloy and the hydrogen storage sites of the entire bulk phase of the hydrogen storage reduce the dehydrogenation temperature of AlH3 and improve the dehydrogenation kinetic performance of AlH3. This facile and effective method significantly improves the dehydrogenation of AlH3 and provides a promising strategy for metal hydride modification.

Excellent kinetics and effective hydrogen storage capacity at low temperature of superlattice rare-earth hydrogen storage alloy by solid-phase treatment

The gaseous hydrogen storage properties of superlattice rare-earth hydrogen storage alloy working at low temperature were investigated and prepared with doping AlH3. The phase composition, kinetic and thermodynamic characteristics of the composite were characterized. The results revealed that the alloy doped with 3 wt% AlH3 had better performance and the maximum hydrogen absorption capacity reached 1.384 wt%, 1.334 wt% and 1.231 wt% at 273 K, 263 K and 253 K, respectively. The hydrogen desorption ability also was enhanced by 202% at 273 K and 192% at 253 K compared to the pristine. The improvement could be ascribed to the solid-phase activation treatment and surface modification using chemical hydride during ball-milling method, which makes it easier for hydrogen desorption.

Gaseous sorption and electrochemical properties of rare-earth hydrogen storage alloys and their representative applications: A review of recent progress

The improvement of hydrogen storage materials is a key issue for storage and delivery of hydrogen energy before its potential can be realized. As hydrogen storage media, rare-earth hydrogen storage materials have been systematically studied in order to improve storage capacity, kinetics, thermodynamics and electrochemical performance. In this review, we focus on recent research progress of gaseous sorption and electrochemical hydrogen storage properties of rare-earth alloys and highlight their commercial applications including hydrogen storage tanks and nickel metal hydride batteries. Furthermore, development trend and prospective of rare-earth hydrogen storage materials are discussed.

Study on Hydrogen in Mixed Gas Separated by Rare Earth Hydrogen Storage Alloys

AB5-type rare-earth nickel (RE-Ni) based hydrogen storage alloys and AB3-type La-Mg-Ni based hydrogen storage alloys were prepared by vacuum medium-frequency induction melting in argon atmosphere. Industrial offgas was simulated by the mixed gas including H2, N2 and CH4. The purity of hydrogen separated by rare-earth hydrogen storage alloys and anti-poison and anti-pulverization properties of the alloys in the process of hydrogen absorption and desorption were studied. The results show that AB5-type RE-Ni based hydrogen storage alloys are possessed of the single structure with CaCu5-type, and AB3-type La-Mg-Ni based hydrogen storage alloys are possessed of the multi-phase structure with (La, Mg) Ni3, LaNi5 and LaNi2 phase. The hydrogen storage alloys will be poisoned by impurity gas in the separation of hydrogen, resulting in lower speed rate of hydrogen absorption and lesser capacity of hydrogen absorption. The anti-pulverization property of La-Mg-Ni based alloys is better than that of LaNi5 alloy and its complex alloy. LaNi3.7Mn0.4Al0.3Fe0.4Co0.2 alloy is considered as better alloy to separate hydrogen from the mixed gas, considering the purity of separated hydrogen, anti-poison and anti-pulverization property of the alloy. The hydrogen purity of 90.7% can be achieved.

Formation cause, composition analysis and comprehensive utilization of rare earth solid wastes

Based on practical situation of rare earth industrial chain, production process and rare earth materials that could produce solid wastes on batch were discussed. Formation cause, formation volume, composition analysis and comprehensive utilization of the solid wastes of rare earth hydrometallurgy slag, electrolysis slag, Fe-based rare earth permanent magnetic materials, Co-based rare earth permanent magnetic materials, rare earth hydrogen storage materials, rare earth polishing powders and rare earth catalysts were comprehensively introduced. Besides, some suggestions on treatment and administration on rare earth solid wastes were put forward.

LaNi 4.5Al 0.5 alloy doped with Au used as anodic materials in a borohydride fuel cell

Fuel cells using borohydride as the fuel have received much attention because of their high thermodynamic cell voltage. Using rare-earth hydrogen storage alloys as the anodic catalyst materials instead of noble metals showed high catalytic activity both in the electrochemical oxidation and the hydrolysis of borohydride. In this work, we doped Au to modify the surface structure of LaNi 4.5Al 0.5 alloy by a self-reduction reaction method. The surface of the alloy particles was evenly covered with Au after treatment. The largest discharge current density increased from about 150 mA cm −2 (discharge to −0.6 V versus Hg/HgO electrode) with the parent alloy to 250 mA cm −2 with the Au-doped alloy. This finding suggested that the electrochemical catalytic activity of the alloy was enhanced after modification with Au. Fuel utilization also increased after modification with Au.

The determination of La, Ce, Pr, Nd, Ni, Co and Mn in rare earth hydrogen storage alloy (AB5 Type) by inductively coupled plasma atomic emission spectrographic method

The determination of La, Ce, Pr, Nd, Ni, Co and Mn in rare earth hydrogen storage alloy (AB5 Type) by inductively coupled plasma atomic emission spectrographic method

Gas Recombination in Sealed Ni-MHx Cells

This paper focuses on investigation of gas recombination in a positive-limited-sealed Ni–MHx cell. The positive electrodes were prepared by electrochemical impregnation of fibrous nickel plaques. The metal hydride negative electrodes were made by pasting the mixture of rare-earth hydrogen storage alloy powders, conducting and binding agents on foamed nickel substrates. The measurement of the positive capacity at different charge times was used to estimate the partial current for oxygen evolution at the same time. The effects of charge rate, electrolyte saturation level and initial state of charge of the positive electrodes on the recombination were investigated in sealed Ni–MHx cells. By determining the differential capacity of nickel hydroxide electrodes, an improved mathematical model was used to evaluate the gas recombination parameters during charge, overcharge, rest and discharge of the positive-limited-sealed Ni–MHx cell. The gas recombination during rest, discharge and overdischarge was also examined. The oxygen recombination on the nickel hydroxide electrodes can be neglected due to the consumption of water when the nickel hydroxide electrodes were discharged. The longer overdischarge produced an increase in cell pressure for the sealed Ni–MHx cell at an electrolyte unsaturated level and the evolving gas can be recombined by a following recharge operation. © 1997 SCI.

Gas Recombination in Sealed Ni–MHx Cells

This paper focuses on investigation of gas recombination in a positive-limited-sealed Ni–MHx cell. The positive electrodes were prepared by electrochemical impregnation of fibrous nickel plaques. The metal hydride negative electrodes were made by pasting the mixture of rare-earth hydrogen storage alloy powders, conducting and binding agents on foamed nickel substrates. The measurement of the positive capacity at different charge times was used to estimate the partial current for oxygen evolution at the same time. The effects of charge rate, electrolyte saturation level and initial state of charge of the positive electrodes on the recombination were investigated in sealed Ni–MHx cells. By determining the differential capacity of nickel hydroxide electrodes, an improved mathematical model was used to evaluate the gas recombination parameters during charge, overcharge, rest and discharge of the positive-limited-sealed Ni–MHx cell. The gas recombination during rest, discharge and overdischarge was also examined. The oxygen recombination on the nickel hydroxide electrodes can be neglected due to the consumption of water when the nickel hydroxide electrodes were discharged. The longer overdischarge produced an increase in cell pressure for the sealed Ni–MHx cell at an electrolyte unsaturated level and the evolving gas can be recombined by a following recharge operation. © 1997 SCI.

The Determination of Thermodynamic Characteristics of Several Rare Earth Hydrogen-Storage Alloys by Electrochemical Method

The Determination of Thermodynamic Characteristics of Several Rare Earth Hydrogen-Storage Alloys by Electrochemical Method