The effect of transition metals on hydrogen migration and catalysis in cast Mg-Ni alloys

The inexpensive fabrication technique of casting is applied to develop new Mg-Ni based hydrogen storage alloys with improved hydrogen sorption properties. A nanostructured eutectic Mg-Mg₂Ni is formed upon solidification which introduces a large area of interfaces along which hydrogen diffusion can occur with high diffusivity. After a few cycles of hydrogenation and dehydrogenation, an ultrafine porous structure formed in the eutectic Mg-Mg₂Ni and some cracks developed along the interface between the eutectic and the α-Mg matrix. This indicates that hydrogen atoms introduced into the alloys preferentially migrate along the interfaces in the nanostructured eutectic which enables effective short-range diffusion of hydrogen. Furthermore, transition metals (TMs) such as Nb, Ti and V in the range 240-560 ppm are added directly to molten Mg-10 wt% Ni alloys and are found to form intermetallic compounds with Ni during solidification. The alloys can store 5.6-6.3 wt% hydrogen at 350 °C and 2 MPa. TM-rich intermetallics distributed homogeneously in the cast alloys appear to play a key role in accelerating the nucleation of Mg from MgH₂ upon dehydrogenation. This leads to a significant improvement in the hydrogen desorption kinetics.     

Hydrogen storage behaviour of Cr- and Mn-doped Mg2Ni alloys fabricated via high-energy ball milling

This paper describes the efficient preparation of an Mg₂Ni alloy for hydrogen storage via high-energy ball milling mechanical alloying for 2 h. The degree of alloy amorphisation increases with increasing ball-milling time. Ball milling for 4 h affords partially amorphous alloys exhibiting the best hydrogen storage performance. Partial substitution of Ni with Cr and Mn improves the hydrogen absorption/desorption thermodynamics, kinetics and cycling performance of the alloy. Specifically, partial Mn substitution improves the cycling performance and reduces the activation energy of the hydrogen desorption reaction, effectively improving the hydrogen desorption kinetic performance. Mg₂Ni_0.8Mn_0.2 shows the best cycling and hydrogen absorption/desorption kinetic performances. Partial Cr substitution reduces the entropy and enthalpy changes of the hydrogen absorption/desorption reaction and effectively reduces the temperature of the initial hydrogen absorption/desorption reaction. In particular, Mg₂Ni_0.9Cr_0.1 shows the best thermodynamic performance.     

Composition dependent microstructure evolution,activation and de-/hydrogenation properties of Mg–Ni–La alloys

In this work, in order to elucidate the effect of different alloying elements on the microstructure, activation and the de-/hydrogenation kinetics performance, the Mg–20La, Mg–20Ni and Mg–10Ni–10La (wt.%) alloys have been prepared by near equilibrium solidification combined with high-energy ball milling treatment to realize the internal optimization as well as particle refinement. The results show that the microstructures of the prepared alloys are significantly refined by forming different types and sizes of intermetallic compounds. Meanwhile, the effects of LaH₃ and Mg₂Ni within the activated samples on de-/hydrogenation kinetics are also discussed. It is observed that the alloy containing LaH₃ preserves stable hydrogenation behavior between 573 and 623 K, while the hydrogenation properties of the alloy containing Mg₂Ni is susceptible to temperature. A preferable hydrogenation performance is observed in Mg–10Ni–10La alloy, which can absorb as high as 5.86 wt% hydrogen within 15 min at 623 K and 3.0 MPa hydrogen pressure. Moreover, the desorption kinetics and the desorption activation energies are evaluated to illustrate the mechanism based on improved dehydrogenation performance. The addition of proper alloying elements Ni and La in combination with reasonable processing is an effective strategy to improve the de-/hydrogenation performance of Mg-based alloys.     

Enhanced hydrogen storage properties of Ti–Cr–Nb alloys by melt-spin and Mo-doping

Ti–Cr–Nb hydrogen storage alloys with a body centered cubic (BCC) structure have been successfully prepared by melt-spin and Mo-doping. The crystalline structure, solidification microstructural evolution, and hydrogen storage properties of the corresponding alloys were characterized in details. The results showed that the hydrogen storage capacity of Ti–Cr–Nb ingot alloys increased from 2.2 wt% up to around 3.5 wt% under the treatment of melt-spin and Mo-doping. It is ascribed that the single BCC phase of Ti–Cr–Nb alloys was stabilized after melt-spin and Mo-doping, which has a higher theoretical hydrogen storage site than the Laves phase. Furthermore, the melt-spin alloy after Mo doping can further effectively increase the de-/absorption plateau pressure. The hydrogen desorption enthalpy change ΔH of the melt-spin alloy decreased from 48.94 kJ/mol to 43.93 kJ/mol after Mo-doping. The short terms cycling test also manifests that Mo-doping was effective in improving the cycle durability of the Ti–Cr–Nb alloys. And the BCC phase of the Ti–Cr–Nb alloys could form body centered tetragonal (BCT) or face center cubic (FCC) hydride phase after hydrogen absorption and transform to the original BCC phase after desorption process. This study might provide reference for developing reversible metal hydrides with favorable cost and acceptable hydrogen storage characteristics.     

Hydrogen storage properties of Mg-23.5Ni-xCu prepared by rapid solidification process and crystallization heat treatment

A Mg-23.5wt%Ni-5wt%Cu alloy was synthesized by the gravity casting method in a large quantity (7.5 kg). From this alloy, Mg-23.5wt%Ni-xwt%Cu (x = 2.5, 5 and 7.5) samples for hydrogen storage were prepared by melt spinning and crystallization heat treatment. The samples were ground under H₂ in order to obtain a fine powder. These alloys contained crystalline Mg and Mg₂Ni phases. The Mg-23.5Ni-2.5Cu alloy had the highest hydriding and dehydriding rates after activation among these alloys. The dehydriding curve under 1.0 bar H₂ at 573 K exhibits two stages; the dehydriding rate is high for about 2.5 min (the decomposition of Mg₂Ni hydride and Mg hydride in small particles), and then it becomes lower (the decomposition of Mg hydride).     

Improving the hydrogen absorption properties of commercial Mg–Zn–Zr alloy

Commercial alloy ZK60 (Mg-6 wt%Zn-0.8 wt% Zr) was used as a hydrogen-storage material to study the effect of cold rolling, ball milling, and plus graphite additives on hydrogen-storage characteristics, hydrogen absorption–desorption behavior, and the related microstructural change of the alloy. Experimental results showed that cold-rolled alloy could not be activated easily. Even after ball milling for 20 h and hydrogen absorption–desorption cycling for 10 times, no saturated hydrogen absorption was observed for cold-rolled alloy. In contrast, alloys with 5 wt% graphite additives could be easily activated after the first hydrogen absorption–desorption cycle, and a saturated hydrogen absorption of 6.9 wt% was obtained after absorption–desorption cycling for five times. A hydrogen absorption of 5.52 wt%, equivalent to 80% of the saturated absorption amount, was measured in 5 min, showing a hydrogen absorption rate of 1.104 wt%/min. The sample reached saturation in 30 min.     

Hydrogenation of Mg and two chosen Mg–Ni alloys

Structure changes during hydrogenation are observed in pure Mg, Mg₂Ni intermetallic (I) and Mg eutectic alloy – 23.5 wt.% Ni (E). Samples were prepared by (i) ball-milling and compacting (alloys I and E) and (ii) by mould casting (Mg and alloy E). Phase composition was checked by SEM and XRD. It was found that the hydrogenated cast alloy I and ball-milled alloy I hydrogenated below the transition temperature T_tr = 508 K contained a much higher amount of low-temperature un-twinned phase LT1 than the ball-milled alloy I hydrogenated above T_tr. It was shown that micro-twinned phase LT2 slows down the rate of hydrogen desorption. Persistent changes of morphology were observed in all materials after the first hydrogen charging cycle which may explain the so-called activation of Mg-based hydrogen-storage materials described in the literature.     

Hydrogen storage properties of Ti0.72Zr0.28Mn1.6V0.4 alloy prepared by mechanical alloying and copper boat induction melting

In the present study, two process techniques, mechanical alloying and innovative vacuum copper boat induction melting, were used to produce Ti_0.72Zr_0.28Mn_1.6V_0.4 alloy for hydrogen storage applications. The hydrogen absorption and desorption properties of the alloy were studied. The material structure and phases were characterized by XRD and SEM. The hydrogen absorption and desorption properties of the alloy were measured by an automatically controlled Sieverts apparatus. The results showed that the samples consisted of two main phases, C14 Lave phase and V-base solid solution phase. The maximum capacity of abs/desorption was achieved at mediate temperature (150 °C). The hydrogen capacity of the induction melted samples in various temperatures was higher than that for the samples produced by mechanical alloying method. The maximum absorption capacity of the induction melted and mechanically alloyed samples were 2 and 1.2 wt%, respectively. The maximum desorption capacity of the induction melted and mechanically alloyed samples were 0.45 and 0.1 wt%, respectively.     

纳米TiO2对Mg-15%Mg2Ni复相合金吸放氢性能的影响

用扩散烧结制备Mg2Ni合金，然后与Mg粉和不同比例(质量百分比分别为0．5％，1.5％，2．5％)的纳米TiO2混和球磨得到纳米Mg—Mg2Ni—TiO2复合储氢材料。对复相合金进行储氢性能研究时发脱，其中添加0．5％TiO2的试样可以在393K，4MPa的条件下4min内吸氢，并能在503K，0．1MPa条件下15min内放氢，放氢量为4．1％；随着温度升高，复合储氢材料放氢量和放氢速度得到提高，在473K吸氢和503K放氢条件下，合金在15min内的放氢量达到5．6％。纳米TiO2对合金吸放氢动力学性能有促进作用。复合储氢材料中增加TiO2含量，加快了放氢速度，略微降低了放氢量。     

Nanoscale microstructures and hydrogenation properties of an as-cast vanadium-based medium-entropy alloy

Vanadium-based hydrogen storage alloys have been widely investigated; however, alloys in the cast state are typically coarse-grained. In this study, an as-cast V₄₅Fe₁₅Ti₂₀Cr₂₀ medium-entropy alloy was prepared by arc melting, and microstructural analysis revealed that the alloy was composed of nanocrystals. The initial pretreatment temperature of the alloy was approximately 100 K lower than that of the as-cast coarse-grained alloy. At room temperature, the time required for the alloy to reach 90% saturation was only 140 s, indicating excellent hydrogen absorption kinetics. The alloy is fully activated after two hydrogen absorption/desorption cycles. The phase transformation of the alloy in the early hydrogenation stage was investigated using X-ray diffraction, and the results showed that the BCC phase was completely transformed into the BCT phase when hydrogen uptake was performed for 6 s. Furthermore, the apparent activation energy of dehydrogenation in the present alloy calculated using the Kissinger method was 69.8 ± 0.8 kJ/mol. The pressure-composition-isotherms tests showed that the hydrogen absorption capacity of the alloy at 295 K was 2.12 wt%. The hydrogenation/dehydrogenation enthalpy change of the alloy was calculated by the Van't Hoff equation, which was 30.90 ± 1.47 and 33.95 ± 0.41 kJ/mol, respectively. The present work demonstrates that nanostructured vanadium-based hydrogen storage alloys can be fabricated using traditional casting techniques. Our study also enriches the understanding of the microstructures of medium-entropy alloys, which may provide positive guidance for the design of novel vanadium-based hydrogen storage alloys.     

Hydrogen storage thermodynamic and dynamic properties of as-milled CeMgNi-based CeMg12-type alloys

Ni was chosen to partially substitute the Mg of alloys to investigate the effect on hydrogen storage dynamics of NdMg₁₂-type alloy. The amorphous and nanocrystalline alloys were synthesized by mechanical milling technology based on CeMg₁₁Ni + x wt% Ni (x = 100, 200) alloys. This paper systematically narrates and investigates the influences of Ni content and milling duration on hydrogen storage performance. Sievert apparatus and differential scanning calorimetry (DSC) were utilized for investigating the de-/hydriding performances of samples. Both Arrhenius and Kissinger methods were utilized in this paper for estimating the dehydrogenation activation energy of hydrides, and found that enhancing Ni content can decrease the thermodynamic parameters (ΔH and ΔS) of alloys slightly and improve the dehydriding dynamics significantly. Furthermore, the hydrogen storage property can be affected significantly by adjusting milling time. With varying milling time, the hydrogen storage capacities can reach the maximum values of 5.691 and 5.904 wt% for x = 100 and 200 alloys separately. The hydrogen absorption saturation ratio (R^a(10)) at 573 K and 3 MPa also obtains maximum values with the variation of milling time, namely 90.17% and 99.32% for x = 100 and 200 alloys separately. The hydrogen desorption ratio (R^d(20)) always increases with milling time increasing. To be specific, prolonging milling time from 5 to 60 h results in the increase of R^d(20) at 593 K from 37.55% to 47.21% for x = 100 alloy and 47.29%–61.70% for x = 200 alloy.     

Hydriding and dehydriding characteristics of nanocrystalline and amorphous Mg20Ni10−xCox (x = 0–4) alloys prepared by melt-spinning

In order to improve the hydriding and dehydriding performances of the Mg₂Ni-type alloys, Ni in the alloy was partially substituted by element Co, and melt-spinning technology was used for the preparation of the Mg₂₀Ni_10−xCo_x (x = 0–4) hydrogen storage alloys. The structures of the as-cast and spun alloys were studied by XRD, SEM and HRTEM. Thermal stability of the as-spun alloys was researched by DSC. The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus. The results showed that no amorphous phase formed in the as-spun Co-free alloy, but the as-spun alloys containing Co showed certain amount of amorphous phase. The hydrogen absorption capacities of the as-cast alloys first increase and then decrease with the variety of Co content. The hydrogen desorption capacities of as-cast and spun alloys rise with increasing Co content. The rapid quenching significantly improved the hydrogenation and dehydrogenation capacities and the kinetics of the alloys. When the quenching rate increased from 0 (as-cast was defined as spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption capacity of the alloys (x = 0) at 200 °C and 1.5 MPa in 20 min rose from 1.39 to 3.12 wt%, and from 1.91 to 2.96 wt% for the alloy (x = 4). The hydrogen desorption capacity of the alloy (x = 0) in 20 min increased from 0.19 to 0.89 wt%, and from 1.39 to 2.15 wt% for the alloy (x = 4).     

Investigation on hydrogen storage properties of as-cast,extruded and swaged Mg–Y–Zn alloys

In this work, three different states of Mg-9.1Y-1.8Zn alloys including as-cast, extruded and swaged were prepared by semi-continuous casting, extrusion and swaging processes, respectively. Their compositions, microstructures and hydrogen storage properties were investigated. The results show that Mg-9.1Y-1.8Zn alloys in three different states are all composed of Mg and long-period stacking ordered (LPSO) phases. The LPSO phases occurs to break and decompose after hydrogenation and in-situ forms the YH_{χ(χ = 2,3)} nano-hydrides. The nano-hydrides can be used as in-situ catalysts to improve the hydrogen storage properties of alloys. Meanwhile, many nanocrystalline grains appear in the core of alloy after swaging, and the average grain size ranges from 80 to 200 nm. The presence of nanocrystals may increase the specific surface area of alloy, facilitating the diffusion and absorption of hydrogen. Comparatively, the swaged alloy exhibits the largest hydrogen storage capacity and excellent hydrogen sorption kinetics relative to other states of alloys.     

Hydrogen storage in TiZrNbFeNi high entropy alloys,designed by thermodynamic calculations

The hydrogen storage properties of the novel equiatomic TiZrNbFeNi and non-equiatomic Ti₂₀Zr₂₀Nb₅Fe₄₀Ni₁₅ high entropy alloys (HEAs) were studied. These alloys were designed with the aid of thermodynamic calculations using the CALPHAD method due to their tendency to form single C14 Laves phase, a phase desirable for room-temperature hydrogen storage. The alloys, which were synthesized by arc melting, showed a dominant presence of C14 Laves phases with the (Zr, Ti)₁(Fe, Ni, Nb, Ti)₂ constitution and small amounts of cubic phases (<1.4 wt%), in good agreement with the thermodynamic predictions. Hydrogen storage properties, examined at room temperature without any activation procedure, revealed that a maximum hydrogen storage capacity was reached for the equiatomic alloy in comparison to the non-equiatomic alloy (1.64 wt% vs 1.38 wt%) in the first cycle; however, the non-equiatomic alloy presented superior reversibility of 1.14 wt% of hydrogen. Such differences on reversibility and capacity among the two alloys were discussed based on the chemical fluctuations of hydride-forming and non-hydride-forming elements, the volume per unit cell of the C14 Laves phases and the distribution of valence electrons.     

Microstructural evolution and hydrogen storage properties of a Ni-modified Mg15Al alloy

On the basis of modification of transition metals on Mg-Al hydrogen storage alloys, Mg15Al5Ni alloy with Ni content of 5 wt% has been prepared by high energy ball mill. The results show that Ni particles uniformly distribute on the surface of particles, while several Ni particles are embedded inside alloy particles. These Ni particles tend to redistribute after hydrogenation. The phase composition analysis reveals the formation of stable Al₃Ni₂ phase in Ni-modified alloy after hydrogenation. The hydrogen absorption performance of Mg15Al5Ni alloy has been improved by introducing Ni, which can absorb 4.36 wt% hydrogen within 5 min at 350 °C. Meanwhile, the activation properties of Mg15Al5Ni alloy can be obviously deteriorated due to the addition of Ni. However, uniformly distributed Al₃Ni₂ nanocrystals with grain sizes around 10 nm hinder grain growth of hydrides, ameliorating hydrogenation kinetics of Mg15Al5Ni alloy. Besides, the modified effect of Ni on hydrogenation kinetics of Mg15Al5Ni alloy has been also discussed in this work.     

Synthesis of low-cost biomass charcoal-based Ni nanocatalyst and evaluation of their kinetic enhancement of MgH2

In this study, a low-cost biomass charcoal (BC)-based nickel catalyst (Ni/BC) was introduced into the MgH₂ system by ball-milling. The study demonstrated that the Ni/BC catalyst significantly improved the hydrogen desorption and absorption kinetics of MgH₂. The MgH₂ + 10 wt% Ni/BC-3 composite starts to release hydrogen at 187.8 °C, which is 162.2 °C lower than the initial dehydrogenation temperature of pure MgH₂. Besides, 6.04 wt% dehydrogenation can be achieved within 3.5 min at 300 °C. After the dehydrogenation is completed, MgH₂ + 10 wt% Ni/BC-3 can start to absorb hydrogen even at 30 °C, which achieved the absorption of 5 wt% H₂ in 60 min under the condition of 3 MPa hydrogen pressure and 125 °C. The apparent activation energies of dehydrogenation and hydrogen absorption of MgH₂ + 10 wt% Ni/BC-3 composites were 82.49 kJ/mol and 23.87 kJ/mol lower than those of pure MgH₂, respectively, which indicated that the carbon layer wrapped around MgH₂ effectively improved the cycle stability of hydrogen storage materials. Moreover, MgH₂ + 10 wt% Ni/BC-3 can still maintain 99% hydrogen storage capacity after 20 cycles. XRD, EDS, SEM and TEM revealed that the Ni/BC catalyst evenly distributed around MgH₂ formed Mg₂Ni/Mg₂NiH₄ in situ, which act as a “hydrogen pump” to boost the diffusion of hydrogen along with the Mg/MgH₂ interface. Meanwhile, the carbon layer with fantastic conductivity enormously accelerated the electron transfer. Consequently, there is no denying that the synergistic effect extremely facilitated the hydrogen absorption and desorption kinetic performance of MgH₂.     

Hydrogen desorption/absorption properties of the extensively cold rolled β Ti–40Nb alloy

β Ti–Nb BCC alloys are potential materials for hydrogen storage in the solid state. Since these alloys present exceptional formability, they can be processed by extensive cold rolling (ECR), which can improve hydrogen sorption properties. This work investigated the effects of ECR accomplished under an inert atmosphere on H₂ sorption properties of the arc melted and rapidly solidified β Ti40Nb alloy. Samples were crushed in a rolling mill producing slightly deformed pieces within the millimeter range size, which were processed by ECR with 40 or 80 passes. Part of undeformed fragments was used for comparison purposes. All samples were characterized by scanning electron microscopy, x-ray diffractometry, energy-dispersive spectroscopy, hydrogen volumetry, and differential scanning calorimetry. After ECR, samples deformed with 40 passes were formed by thick sheets, while several thin layers composed the specimens after 80 passages. Furthermore, deformation of β Ti–40Nb alloys synthesized samples containing a high density of crystalline defects, cracks, and stored strain energy that increased with the deformation amount and proportionally helped to overcome the diffusion's control mechanisms, thus improving kinetic behaviors at low temperature. Such an improvement was also correlated to the synergetic effect of resulting features after deformation and thickness of stacked layers in the different deformation conditions. At the room temperature, samples deformed with 80 passes absorbed ∼2.0 wt% of H₂ after 15 min, while samples deformed with 40 passes absorbed ∼1.8 wt% during 2 h, excellent results if compared with undeformed samples hydrogenated at 300 °C that acquired a capacity of ∼1.7 wt% after 2 h. The hydrogen desorption evolved in the same way as for absorption regarding the deformation amount, which also influenced desorption temperatures that were reduced from ∼270 °C, observed for the undeformed and samples deformed with 40 passes, to ∼220 °C, for specimens rolled with 80 passes. No significant loss in hydrogen capacity was observed in the cold rolled samples.     

Comparison of hydrogen storage properties of Ti0.37V0.38Mn0.25 alloys prepared by mechanical alloying and vacuum arc melting

Two process methods, mechanical alloying and vacuum arc melting, were used to prepare Ti_0.37V_0.38Mn_0.25 alloy powders for studying their differences in hydrogen storage capacities. Ti_0.37V_0.38Mn_0.25 samples produced by mechanical alloying showed an amorphous structure and a maximum hydrogen absorption of 1.76 wt%, but those prepared by vacuum arc melting exhibited a single phase BCC structure with no Laves phase, as well as a maximum hydrogen absorption of 3.62 wt%. The hydride in Ti_0.37V_0.38Mn_0.25 alloy after hydrogen absorption was VH₂, whose low reaction temperature allows for large amount of hydrogen absorption at ambient temperature. The hydride was, however, unstable and decomposed completely at relatively low hydrogen desorption temperature of 200 °C. After absorption–desorption cycling for 100 times, the mechanically alloyed powders, which did not pulverize as much as those of the arc-melting derived powders, showed smaller decline in hydrogen-absorption capability.     

Hydrogen storage properties of Ti1.4V0.6Ni + x Mg (x = 1–3, wt.%) alloys

We prepared Ti_1.4V_0.6Ni ribbons by arc-melting and subsequent melt-spinning techniques. Ti_1.4V_0.6Ni + x Mg (x = 1, 1.5, 2, 2.5 and 3, wt.%) composite alloys were obtained by the mechanical ball-milling method. The structures and hydrogen storage properties of alloys were investigated. Ti_1.4V_0.6Ni + x Mg composite alloys contained icosahedral quasicrystalline phase, Ti₂Ni-type phase, β-Ti solid-solution phase and metallic Mg. The electrochemical and gaseous hydrogen storage properties of alloys were improved with Mg addition. Ti_1.4V_0.6Ni + 2 Mg alloy showed maximum electrochemical discharge capacity of 282.5 mAh g⁻¹ as well as copacetic high-rate discharge ability of 82.3% at the discharge current density of 240 mA g⁻¹ compared with that of 30 mA g⁻¹, and the cycling life achieved above 200 mAh g⁻¹ after 50 consecutive cycles of charging and discharging. The hydrogen absorption/desorption properties of Ti_1.4V_0.6Ni + x Mg (x = 1, 2 and 3, wt.%) alloys were better than Ti_1.4V_0.6Ni. Ti_1.4V_0.6Ni + 3 Mg alloy also exhibited a favorable hydrogen absorption capacity of 1.53 wt.%. The improvement in the hydrogen storage characteristics caused by adding Mg may be ascribed to better hydrogen diffusion and anti-corrosion ability.     

Remarkable enhancement in durability of ZrCo alloy against hydrogen induced disproportionation by Ti and Nb co-substitution

Considering the thermodynamic stability of various hydrides, a strategy has been employed to improve the hydrogen isotope storage properties of ZrCo alloy which involves partial co-substitution of Zr with Ti and Nb. Herein, alloys of composition Zr_0.8Ti_0.2-xNb_xCo (x = 0.05, 0.1, 0.15) is prepared, characterized and the effect of Ti and Nb doping on hydrogen storage properties of parent ZrCo alloy is investigated. XRD analysis confirmed the formation of desired pure cubic phase of all the synthesized alloys similar to ZrCo phase. The presence of a single plateau in hydrogen desorption pressure-composition isotherms confirms single step hydrogen absorption-desorption behavior in Zr_0.8Ti_0.2-xNb_xCo alloys. The equilibrium pressure of hydrogen desorption decreases marginally with increasing Nb content in Zr_0.8Ti_0.2-xNb_xCo alloys which is further corroborated by differential scanning calorimetry measurements. Investigation of hydrogen induced disproportionation behavior in ITER-simulating condition revealed substantial impact of co-substitution of Ti and Nb on anti-disproportionation properties of ZrCo alloy. These remarkable properties make the Ti and Nb co-substituted quaternary alloys a desirable material for hydrogen isotope storage and delivery application.