Electrochemical Hydrogen Storage Kinetics Research Articles

Ameliorated Hydrogen Storage Kinetics of Mg20Ni7M3 (M=Co, Cu) Alloys by Melt Spinning

In order to obtain a nanocrystalline and amorphous structure in the Mg2Ni-type alloy, the melt spinning was applied to fabricate the Mg20Ni7M3 (M=Co, Cu) hydrogen storage alloys. The microstructures of the alloys were characterized by XRD, SEM and HRTEM. The effects of the melt spinning on the gaseous and electrochemical hydrogen storage kinetics of the alloys were investigated. The results indicate that the as-spun (M=Co) alloys display a nanocrystalline and amorphous structure as spinning rate grows to 20 m/s, while the as-spun (M=Cu) alloys hold an entire nanocrystalline structure even if a limited spinning rate is applied, suggesting that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. The melt spinning remarkably ameliorates the gaseous hydriding and dehydriding kinetics of the alloys. The hydrogen absorption ratio ( ) and hydrogen desorption ratio ( ) are enhanced from 81.9% to 94.7% and from 34.9% to 57.3% for the (M=Co) alloy, and from 57.2% to 92.8% and from 21.6% to 49.6% for the (M=Cu) alloy by raising spinning rate from 0 (as-cast was defined as the spinning rate of 0 m/s) to 30 m/s. Furthermore, the high rate discharge ability (HRD), the limiting current density (IL) and the hydrogen diffusion coefficient (D) of the alloys notably increase with the growing of the spinning rate.

An Investigation of the Electrochemical Hydrogen Storage Performances of the RE-Mg-Ni-Based A<sub>2</sub>B<sub>7</sub>-Type Electrode Alloys Prepared by Melt Spinning

The RE-Mg-Ni-based A2B7-type La0.75−xPrxMg0.25Ni3.2Co0.2Al0.1 (x = 0, 0.1, 0.2, 0.3, 0.4) electrode alloys were synthesized by melt spinning technology. The impacts of the melt spinning and the substitution of Pr for La on the microstructures and electrochemical characteristics of the alloys were investigated in detail. The results reveal that the as-cast and spun alloys have a multiphase structure, containing two main phases (La, Mg)2Ni7 and LaNi5 as well as a residual phase LaNi2. The melt spinning results in a notable grain refinement of the alloys without altering the phase structure of the alloys. The discharge capacity of the (x=0.1) alloy first mounts up and then falls with rising the spinning rate. And the as-spun (10 m/s) alloy yields the maximum discharge capacity with the variation of Pr content. Furthermore, the measurements of the electrochemical hydrogen storage kinetics reveal that the high rate discharge ability (HRD), the hydrogen diffusion coefficient (D) and the limiting current density (IL) of the alloys first increases then decreases with rising the spinning rate and the amount of Pr substitution.

Preparation and Hydrogen Storage Kinetics of Nanocrystalline and Amorphous Mg<sub>20</sub>Ni<sub>10-x</sub>M<sub>x</sub> (M=Co, Cu; x=0-4) Alloys

In order to obtain a nanocrystalline and amorphous structure in the Mg2Ni-type alloy, the Ni in Mg2Ni alloy has been partially substituted by M (M=Co, Cu), and the melt spinning has been used to fabricate the Mg20Ni10-xMx (M=Co, Cu; x=0-4) hydrogen storage alloys. The microstructures of the alloys were characterized by XRD, SEM and HRTEM. The effects of substituting Ni with M (M=Co, Cu) on the gaseous and electrochemical hydrogen storage kinetics of the as-spun alloys were investigated. The results indicate that the as-spun (M=Co) alloys display a nanocrystalline and amorphous structure, while the as-spun (M=Cu) alloys hold an entire nanocrystalline structure, suggesting that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. The substitution of M (M=Co, Cu) for Ni exerts a trifling impact on the hydriding kinetics of the alloys, but it renders a marked enhancement of dehydriding capacity and kinetics. Furthermore, the measurements of the high rate discharge ability (HRD) and the hydrogen diffusion coefficient (D) as well as the electrochemical impedance spectra (EIS) of the alloys exhibit that the electrochemical kinetics of the as-spun (30 m/s) alloys is significantly ameliorated by substituting Ni with M (M=Co, Cu).

Investigation of Electrochemical Hydrogen Storage Kinetics of Melt Spun Nanocrystalline and Amorphous Mg2Ni-type Alloy

Abstract The Mg 2 Ni-type Mg 2 Ni 1− x Co x ( x =0, 0.1, 0.2, 0.3, 0.4) alloys were prepared by melt-spinning technique. The structures of the as-cast and spun alloys were characterized by XRD, SEM and TEM. The electrochemical hydrogen storage kinetics of the as-spun alloy ribbons was tested by an automatic galvanostatic system. The hydrogen diffusion coefficients in the alloys were calculated by virtue of potential-step method. The electrochemical impedance spectrums (EIS) and the Tafel polarization curves were plotted by an electrochemical workstation. The results show that the as-spun Co-free alloy exhibits a typical nanocrystalline structure, while the as-spun ( x =0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg 2 Ni-type alloy. The amorphization degree of the as-spun alloys substituted by Co visibly increases with the increase in the amount of Co replacement. The Co replacement for Ni notably improves the electrochemical hydrogen storage kinetics of the alloys. With a growth in the amount of Co replacement from 0 to 0.4, the high rate discharge ability of the as-spun (25 m/s) alloy increases from 65.3% to 75.3%, the hydrogen diffusion coefficient ( D ) from 2.22 to 3.34 cm 2 /s and the limiting current density I L from 247.8 to 712.4 mA/g, respectively.

Improved Physical and Electrochemical Hydrogen Storage Kinetics of the Mg<sub>20</sub>Ni<sub>10-X</sub>Mx (M=Cu, Co; X=0, 4) Alloys by Melt Spinning

It has come to light that the Mg2Ni-type alloy with a nanocrystalline/amorphous structure possesses superior hydrogen storage kinetics. The Mg2Ni-type Mg20Ni10-xMx (M=Cu, Co; x=0, 4) hydrogen storage alloys were synthesized by a melt-spinning technique. The microstructures of the as-cast and spun alloys were characterized by XRD, SEM and HRTEM. The gaseous and electrochemical hydrogen storage kinetics of the alloys was measured. The results show that whatever spinning rate the as-spun (M=Cu) alloys hold an entire nanocrystalline structure. As spinning rate approaches to 20 m/s, the as-spun (M=Co) alloys display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. Furthermore, such substitution results in the formation of secondary phases Mg2Cu and MgCo2 instead of changing the major phase of Mg2Ni. The melt spinning markedly improves the gaseous and electrochemical hydrogen storage kinetics of the alloys. The hydrogen absorption ratio (R5a ), hydrogen desorption ratio (R20d ) and the high rate discharge ability (HRD) notably mount up with the growing of the spinning rate.

Improved Physical and Electrochemical Hydrogen Storage Kinetics of the As-Spun Mg<sub>2</sub>Ni-Type Alloys by Substituting Ni with M (M=Co, Cu)

In order to improve the physical and electrochemical hydrogen storage kinetics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by M (M=Co, Cu). Melt-spinning technology was used for the preparation of the Mg20Ni10-xMx (M=Co, Cu; x=0, 1, 2, 3, 4) hydrogen storage alloys. The structures of the as-cast and spun alloys are characterized by XRD, SEM and TEM. The physical and electrochemical hydrogen storage kinetics of the alloys is measured. The results show that the as-spun (M=Cu) alloys hold an entire nanocrystalline structure, whereas the as-spun (M=Co) alloys exhibit a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. The substitution of M (M=Co, Cu) for Ni engenders an insignificant effect on the hydrogen absorption kinetics of the alloys, but it markedly ameliorates the hydrogen desorption kinetics of the alloys and the high rate discharge ability. With an increase of the M (M=Co, Cu) content from 0 to 4, the hydrogen desorption ratio ( ) is enhanced form 20.0% to 65.43% for the as-spun (20 m/s) alloy (M=Co), and from 20.0% to 52.88% for the as-spun (20 m/s) alloy (M=Cu).

Electrochemical Hydrogen Storage Kinetics of La0.75-x ZrxMg0.25Ni3.2Co0.2Al0.1 (x = 0-0.2) Alloys Prepared by Melt Spinning

The RE–Mg–Ni-based A2B7-type La0.75–xZrxMg0.25Ni3.2Co0.2Al0.1 (x = 0, 0.05, 0.1, 0.15, 0.2) electrode alloys were fabricated by casting and melt spinning. The influences of the melt spinning on the structures and the electrochemical hydrogen storage kinetics of the alloys were investigated. The structure characterized by XRD, SEM and HRTEM and the results reveal that the as-cast and spun alloys have a multiphase structure, composing of two main phases (La, Mg)2Ni7 and LaNi5 as well as a residual phase LaNi2. The as-spun Zr-free alloy displays an entire nanocrystalline structure, but a like amorphous structure is detected in the as-spun alloy substituted by Zr, suggesting that the substitution of Zr for La facilitate the amorphous formation. The melt spinning engenders different impact on the high rate discharge ability (HRD) of the Zr-free and Zr substitution alloys. As the spinning rate is enhanced from 0 (As-cast is defined as the spinning arte of 0 m/s) to 20 m/s, the HRD of the Zr-free (x = 0) alloy grows from 94.28% (0 m/s) to 95.15% (10 m/s) and then declines to 89.23% (20 m/s). And that of the Zr substitution (x = 0.15) alloy monotonously falls from 90.45% to 80.07%. Furthermore, the electrochemical impedance spectrum (EIS), the Tafel polarization curves and the potential-step measurements all indicate that the electrochemical kinetics first increases then decreases for the Zr-free alloy, but all of them always decline for the alloy substituted by Zr with the growing of spinning rate.

Improved the Physical and Electrochemical Hydrogen Storage Kinetics of Mg<sub>2</sub>Ni-Type Alloys by Substituting Ni with Co and Melt Spinning

In this paper, melt-spinning technology was used for preparing Mg20Ni10-xCox (x = 0, 1, 2, 3, 4) hydrogen storage alloys. The influences of both the Co substitution and the melt spinning on the the physical and electrochemical hydrogen storage kinetics of the alloys were investigated. The XRD, SEM and TEM characterization exhibits that the as-spun Co-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys substituted by Co display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. The Co substitution gives rise to forming secondary phase MgCo2 without altering the Mg2Ni major phase of the alloys. The measurement of the physical and electrochemical hydrogen storage kinetics of the alloys shows that both the melt spinning and the substitution of Co for Ni markedly improve the physical hydriding and dehydriding kinetics and the electrochmeical kinetics (HRD) of the alloys.

Gaseous and Electrochemical Hydrogen Storage Kinetics of as-Spun Nanocrystalline Mg<sub>20</sub>Ni<sub>10-x</sub>Cu<sub>x</sub> (x = 0-4) Alloys

In order to improve the gaseous and electrochemical hydrogen storage kinetics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by element Cu. Melt-spinning technology was used for the preparation of the Mg20Ni10-xCux (x = 0, 1, 2, 3, 4) hydrogen storage alloys. The structures of the as-cast and spun alloys are characterized by XRD, SEM and TEM. The gaseous hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys is tested by an automatic galvanostatic system. The results show that all the as-spun alloys hold an entire nanocrystalline structure and are free of amorphous phase. The substitution of Cu for Ni, instead of changing the major phase Mg2Ni, leads to a visible refinement of the grains of the as-cast alloys. Furthermore, both the melt spinning treatment and Cu substitution significantly improve the gaseous and electrochemical hydrogen storage kinetics of the alloys.

An Investigation on the Gaseous and Electrochemical Hydrogen Storage Kinetics of As-Spun Nanocrystalline Mg<sub>20</sub>Ni<sub>10-x</sub>CO<sub>x</sub> (x=0-4) Alloys

In order to improve the gaseous and electrochemical hydrogen storage kinetics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by element Co. Melt-spinning technology was used for the preparation of the Mg20Ni10-xCox (x=0, 1, 2, 3, 4) hydrogen storage alloys. The structures of the as-cast and spun alloys are characterized by XRD, SEM and TEM. The gaseous hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys is tested by an automatic galvanostatic system. The results show that the as-spun Co-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys substituted by Co display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. Both the melt spinning and the substitution of Co for Ni evidently ameliorate the hydriding and dehydriding kinetics and the HRD of the alloys. With an increase in the spinning rate from 0 (As-cast was defined as spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption saturation ratio ( ) of the Co4 alloy grows from 77.1 to 93.5 wt.%, the hydrogen desorption ratio ( ) from 54.5% to 70.2%, the HRD from 60.3% to 76.0%, respectively.

Enhanced hydrogen storage kinetics of nanocrystalline and amorphous Mg 2N-type alloy by substituting Ni with Co

In order to improve the hydrogen storage kinetics of the Mg 2Ni-type alloys, Ni in the alloy was partially substituted with element Co. The Mg 2Ni-type Mg 2Ni 1- x Co x ( x=0, 0.1, 0.2, 0.3, 0.4) alloys were fabricated by melt-spinning technique. The structures of the as-spun alloys were characterized by XRD and TEM. The gaseous and electrochemical hydrogen storage kinetics of the alloys was measured. The results show that the substitution of Co for Ni notably enhances the glass forming ability of the Mg 2Ni-type alloy. The amorphization degree of the alloys visibly increases with rising of Co content. Furthermore, the substitution of Co for Ni significantly improves the hydrogen storage kinetics of the alloys. With an increase in the amount of Co substitution from 0 to 0.4, the hydrogen absorption saturation ratio of the as-spun (15 m/s) alloy increases from 81.2% to 84.9%, the hydrogen desorption ratio from 17.60% to 64.79%, the hydrogen diffusion coefficient increases from 1.07×10 −11 to 2.79×10 −11 cm 2/s and the limiting current density increases from 46.7 to 191.7 mA/g, respectively.

Gaseous and electrochemical hydrogen storage kinetics of nanocrystalline Mg 2Ni-type alloy prepared by rapid quenching

The nanocrystalline Mg 2Ni-type Mg 2Ni 1− x Cu x ( x = 0, 0.1, 0.2, 0.3, 0.4) alloys were synthesized by direct melt quenching technique. The structures of the as-cast and quenched alloys were investigated by XRD, SEM and HRTEM. The gaseous hydrogen storage kinetics of the alloys was measured using an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the alloys was tested by using constant current to charge and discharge the electrode. The results indicate that the substitution of Cu notably rendered the grain refinement of the as-cast alloys without altering the major phase Mg 2Ni. All the as-quenched alloys exhibit a nanocrystalline structure without the presence of any amorphous phase. It is found that the substitution of Cu for Ni and rapid quenching significantly ameliorated the gaseous and electrochemical hydrogen storage kinetics of the nanocrystalline Mg 2Ni 1− x Cu x ( x = 0–0.4) alloys. Furthermore, both the rapid quenching treatment and the Cu substitution results in a notable increase in the hydrogen diffusion coefficient ( D) as well as the limiting current density ( I L) but an obvious decline in the electrochemical impedance.

Enhanced Hydrogen Storage Kinetics of Nanocrystalline and Amorphous Mg₂Ni-type Alloy by Melt Spinning.

Mg2Ni-type Mg2Ni1−xCox (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were fabricated by melt spinning technique. The structures of the as-spun alloys were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys was tested by an automatic galvanostatic system. The results show that the as-spun (x = 0.1) alloy exhibits a typical nanocrystalline structure, while the as-spun (x = 0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni notably intensifies the glass forming ability of the Mg2Ni-type alloy. The melt spinning treatment notably improves the hydriding and dehydriding kinetics as well as the high rate discharge ability (HRD) of the alloys. With an increase in the spinning rate from 0 (as-cast is defined as spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption saturation ratio () of the (x = 0.4) alloy increases from 77.1 to 93.5%, the hydrogen desorption ratio () from 54.5 to 70.2%, the hydrogen diffusion coefficient (D) from 0.75 × 10−11 to 3.88 × 10−11 cm2/s and the limiting current density IL from 150.9 to 887.4 mA/g.

Advanced hydrogen storage alloys for Ni/MH rechargeable batteries

Hydrogen storage alloys are of particular interest as a novel group in functional materials owing to their potential and practical applications in Ni/MH rechargeable batteries. This review is devoted to the specific alloy families developed for high-energy and high-power Ni/MH batteries in the last decades, especially for EV, HEV and PHEV applications. The scope of the work encompasses principles of Ni/MH batteries, electrochemical hydrogen storage thermodynamics and kinetics, prerequisites for hydrogen storage electrode alloys and recent advances in hydrogen storage electrode alloys. Rare earth AB5-type alloys, Ti- and Zr-based AB2-type alloys, Mg-based amorphous/nanocrystalline alloys, rare earth-Mg–Ni-based alloys and Ti–V-based alloys are highlighted. Additionally, the challenges met in developing advanced hydrogen storage alloys for Ni/MH rechargeable batteries are pointed out and some research directions are suggested.

An investigation of hydrogen storage kinetics of melt-spun nanocrystalline and amorphous Mg 2Ni-type alloys

The nanocrystalline and amorphous Mg 2Ni-type Mg 2- x La x Ni( x=0, 0.2) hydrogen storage alloys were synthesized by melt-spinning technique. The as-spun alloy ribbons were obtained. The microstructures of the as-spun ribbons were characterized by X-ray diffraction (XRD), high resolution transmission electronic microscopy (HRTEM) and electron diffraction (ED). The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus, and their electrochemical kinetics were tested by an automatic galvanostatic system. The electrochemical impedance spectrums (EIS) were plotted by an electrochemical workstation (PARSTAT 2273). The hydrogen diffusion coefficients in the alloys were calculated by virtue of potential-step method. The obtained results showed that no amorphous phase was detected in the as-spun La-free alloy, but the as-spun alloys substituted by La held a major amorphous phase, confirming that the substitution of La for Mg markedly intensified the glass forming ability of the Mg 2Ni-type alloy. The substitution of La for Mg notably improved the electrochemical hydrogen storage kinetics of the Mg 2Ni-type alloy. Furthermore, the hydrogen storage kinetics of the experimental alloys was evidently ameliorated with the spinning rate growing.

An investigation on hydrogen storage kinetics of nanocrystalline and amorphous Mg 2Ni 1− xCo x ( x = 0–0.4) alloy prepared by melt spinning

In order to improve the hydrogen storage kinetics of the Mg 2Ni-type alloys, Ni in the alloy was partially substituted by element Co, and melt-spinning technology was used for the preparation of the Mg 2Ni 1− x Co x ( x = 0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys. The structures of the as-cast and spun alloys are characterized by XRD, SEM and TEM. The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys is tested by an automatic galvanostatic system. The hydrogen diffusion coefficients in the alloys are calculated by virtue of potential-step method. The electrochemical impedance spectrums (EIS) and the Tafel polarization curves are plotted by an electrochemical workstation. The results show that the substitution of Co for Ni notably enhances the glass forming ability of the Mg 2Ni-type alloy. Furthermore, the substitution of Co for Ni, instead of changing major phase Mg 2Ni, leads to forming secondary phases MgCo 2 and Mg. Both the melt spinning treatment and Co substitution significantly improve the hydrogen absorption and desorption kinetics. The high rate discharge ability, the hydrogen diffusion coefficient and the limiting current density of the alloys significantly increase with raising both the spinning rate and the amount of Co substitution.