• Energy Research

LaNiSn and NdNiSn compounds and their deuterides have been studied by variable temperature 119Sn Mossbauer spectroscopy. The hyperfine parameters obtained experimentally are in good agreement with those derived from first principle calculations. The enlargement of quadrupole splitting observed for LaNiSn after deuteration confirms the lower symmetry of electron density around tin atoms indicated by the calculation of partial Sn-p density of states (DOS). Magnetic ordering is observed at low temperature in deuterided NdNiSn.

LaNiSn and NdNiSn compounds and their deuterides have been studied by variable temperature 119Sn Mossbauer spectroscopy. The hyperfine parameters obtained experimentally are in good agreement with those derived from first principle calculations. The enlargement of quadrupole splitting observed for LaNiSn after deuteration confirms the lower symmetry of electron density around tin atoms indicated by the calculation of partial Sn-p density of states (DOS). Magnetic ordering is observed at low temperature in deuterided NdNiSn.

The performance of cylindrical cells made from negative electrode active materials of two selected AB2 metal hydride chemistries with different dominating Laves phases (C14 vs. C15) were compared. Cells made from Alloy C15 showed a higher high-rate performance and peak power with a corresponding sacrifice in capacity, low-temperature performance, charge retention, and cycle life when compared with the C14 counterpart (Alloy C14). Annealing of the Alloy C15 eliminated the ZrNi secondary phase and further improved the high-rate and peak power performance. This treatment on Alloy C15 showed the best low-temperature performance, but also contributed to a less-desirable high-temperature voltage stand and an inferior cycle stability. While the main failure mode for Alloy C14 in the sealed cell is the formation of a thick oxide layer that prevents gas recombination during overcharge and consequent venting of the cell, the failure mode for Alloy C15 is dominated by continuous pulverization related to the volumetric changes during hydride formation and hysteresis in the pressure-composition-temperature isotherm. The leached-out Mn from Alloy C15 formed a high density of oxide deposits in the separator, leading to a deterioration in charge retention performance. Large amounts of Zr were found in the positive electrode of the cycled cell containing Alloy C15, but did not appear to harm cell performance. Suggestions for further composition and process optimization for Alloy C15 are also provided.

The performance of cylindrical cells made from negative electrode active materials of two selected AB2 metal hydride chemistries with different dominating Laves phases (C14 vs. C15) were compared. Cells made from Alloy C15 showed a higher high-rate performance and peak power with a corresponding sacrifice in capacity, low-temperature performance, charge retention, and cycle life when compared with the C14 counterpart (Alloy C14). Annealing of the Alloy C15 eliminated the ZrNi secondary phase and further improved the high-rate and peak power performance. This treatment on Alloy C15 showed the best low-temperature performance, but also contributed to a less-desirable high-temperature voltage stand and an inferior cycle stability. While the main failure mode for Alloy C14 in the sealed cell is the formation of a thick oxide layer that prevents gas recombination during overcharge and consequent venting of the cell, the failure mode for Alloy C15 is dominated by continuous pulverization related to the volumetric changes during hydride formation and hysteresis in the pressure-composition-temperature isotherm. The leached-out Mn from Alloy C15 formed a high density of oxide deposits in the separator, leading to a deterioration in charge retention performance. Large amounts of Zr were found in the positive electrode of the cycled cell containing Alloy C15, but did not appear to harm cell performance. Suggestions for further composition and process optimization for Alloy C15 are also provided.

Abstract Desalination is an important method to take full advantage of the sea water to produce fresh water. However, the systems or devices reported previously still have the limitations in the energy supply and portability when used in some specific application scenarios, such as island and remote coastal area. In this paper, a multi-function desalination system is proposed, which could provide fresh water, electrical energy, and even the cold energy based on the hydrolysis reaction of hydride and fuel cell water recovery. Besides, the system could be modified to increase the flexibility of the system operation to satisfy the various energy demands under different conditions. A lumped parameter model of the proposed system is developed to evaluate the system performance. The results show that the fuel cell helps to increase the absolute humidity of the wet air by 15.5% and to increase the water production by condensing the wet air by 1.8 times compared with simple water harvest from the ambient environment. The modified system demonstrates more stable performance of the water production than the original desalination system, which means that the modified system is less affected by the parameter variation. The maximum water production of the kW level system could achieve 11.10 kg/h. Comparing with the previous reports, the unit power consumption of the modified system could reach the lowest level (about 880 Wh/kg), showing the promising water production performance of the system developed in this work.

Abstract Desalination is an important method to take full advantage of the sea water to produce fresh water. However, the systems or devices reported previously still have the limitations in the energy supply and portability when used in some specific application scenarios, such as island and remote coastal area. In this paper, a multi-function desalination system is proposed, which could provide fresh water, electrical energy, and even the cold energy based on the hydrolysis reaction of hydride and fuel cell water recovery. Besides, the system could be modified to increase the flexibility of the system operation to satisfy the various energy demands under different conditions. A lumped parameter model of the proposed system is developed to evaluate the system performance. The results show that the fuel cell helps to increase the absolute humidity of the wet air by 15.5% and to increase the water production by condensing the wet air by 1.8 times compared with simple water harvest from the ambient environment. The modified system demonstrates more stable performance of the water production than the original desalination system, which means that the modified system is less affected by the parameter variation. The maximum water production of the kW level system could achieve 11.10 kg/h. Comparing with the previous reports, the unit power consumption of the modified system could reach the lowest level (about 880 Wh/kg), showing the promising water production performance of the system developed in this work.

This work focused on the high pressure PCT and in situ neutron powder diffraction studies of the LaMg2Ni9-H2 (D2) system at pressures up to 1,000 bar. LaMg2Ni9 alloy was prepared by a powder metallurgy route from the LaNi9 alloy precursor and Mg powder. Two La3−xMgxNi9 samples with slightly different La/Mg ratios were studied, La1.1Mg1.9Ni9 (sample 1) and La0.9Mg2.1Ni9 (sample 2). In situ neutron powder diffraction studies of the La1.09Mg1.91Ni9D9.5 (1) and La0.91Mg2.09Ni9D9.4 (2) deuterides were performed at 25 bar D2 (1) and 918 bar D2 (2). The hydrogenation properties of the (1) and (2) are dramatically different from those for LaNi3. The Mg-containing intermetallics reversibly form hydrides with DHdes = 24.0 kJ/molH2 and an equilibrium pressure of H2 desorption of 18 bar at 20 °C (La1.09Mg1.91Ni9). A pronounced hysteresis of H2 absorption and desorption, ~100 bar, is observed. The studies showed that LaNi5-assisted hydrogenation of MgNi2 in the LaMg2Ni9 hybrid structure takes place. In the La1.09Mg1.91Ni9D9.5 (1) and La0.91Mg2.09Ni9D9.4 (2) (a = 5.263/5.212; c = 25.803/25.71 Å) D atoms are accommodated in both Laves and CaCu5-type slabs. In the LaNi5 CaCu5-type layer, D atoms fill three types of interstices; a deformed octahedron [La2Ni4], and [La(Mg)2Ni2] and [Ni4] tetrahedra. The overall chemical compositions can be presented as LaNi5H5.6/5.0 + 2*MgNi2H1.95/2.2 showing that the hydrogenation of the MgNi2 slab proceeds at mild H2/D2 pressure of just 20 bar. A partial filling by D of the four types of the tetrahedral interstices in the MgNi2 slab takes place, including [MgNi3] and [Mg2Ni2] tetrahedra.