What was the onset dehydrogenation temperature for nano-V2O3@C-catalyzed MgH2?
Click to see answer
215 °C.
Click to see question
What was the onset dehydrogenation temperature for nano-V2O3@C-catalyzed MgH2?
215 °C.
What type of nanoparticles were synthesized to improve hydrogen storage properties of MgH2?
ZrMn2 intermetallic nanoparticles with sizes ranging from 100 to 300 nm.
What effect do TiC nanoparticles have on the dehydrogenation temperatures of MgH2?
They reduce the onset and peak temperatures of H2 desorption to 190 °C and 280 °C, respectively.
What hydrogen absorption capacity was achieved by the Mg-Ti nanocomposite at room temperature?
6.2 wt% H2 within 2 hours at 3 MPa.
How much faster does hydrogen diffuse in the new composite compared to commercial MgH2?
About 40 times faster.
How were Mg nanoparticles synthesized?
By reducing di-n-butylmagnesium (MgBu2) in THF solution containing lithium and naphthalene.
Why are nanoscale catalysts more effective than conventional catalysts for MgH2?
They generate more active catalytic sites due to intimate contacts with MgH2.
What is the maximum hydrogen absorption temperature for Mg nanoparticles?
Below 150 °C.
What is the significance of Ti in the MgH2 nanocrystalline preparation?
Ti catalyzes the reaction of Mg with anthracene and TiCl4 in THF solution.
What was the dehydrogenation onset temperature for the 4 mol% Ni NF-catalyzed MgH2?
143 °C.
What is the energy density of hydrogen?
142 MJ/kg.
What are the main challenges in the kinetics of MgH2?
High thermal stability (ΔH = 76 kJ/mol) and kinetic barrier (Ea = 160 kJ/mol).
Which transition metal compounds have been developed to improve the hydrogen-storage properties of MgH2?
Nb, V, Co, Fe, Zr, and Ce-based compounds.
Which transition metal is recognized as the best-performing catalyst for MgH2?
Titanium (Ti).
At what temperature does hydrogen desorption occur for Mg nanoparticles?
Above 300 °C.
What was the hydrogen absorption capacity of the Mg-TiH nanocomposite at room temperature?
4.3 wt% H2 in 10 minutes.
What is the significance of Na2Ti3O7 nanotubes in improving MgH2 performance?
They showed superior catalytic effects, lowering the onset dehydrogenation temperature significantly.
What was the hydrogen absorption and release temperature for Mg nano fibers?
Absorbed at 300 °C and released at 360 °C.
What is the impact of Grignard reagents on MgH2 synthesis?
The types of Mg precursors and synthesis conditions significantly influence the morphologies and hydrogen storage properties.
What was the hydrogen absorption capacity of the Mg@Ni8Gn2 composite at 100 °C?
6.28 wt% of hydrogen in 100 seconds.
What are metal-organic frameworks (MOFs) used for in this context?
To synthesize carbon-wrapped transition metal catalysts.
What strategies have been proposed to improve the thermodynamics and kinetics of MgH2?
Alloying, nanostructuring, and catalyzing.
What happens to the size of Mg nanoparticles with increasing lithium/naphthalene ratios?
The particle size decreases.
What role does multiple valence Ti play in the MgH2 system?
Acts as intermediate and catalytic active sites for electron transfers.
What was the average particle size of the Mg-Ti nanocomposite synthesized from THF solution?
About 50 nm.
What is the peak dehydrogenation temperature for the MgH2-5 wt% Ni@rGO composite?
247 °C.
What effect does Ni doping have on MgH2?
It significantly decreases the activation energy for hydrogen desorption.
What type of nanoparticles were synthesized to lower the onset temperature of dehydrogenation to 180 °C?
Amorphous NiB nanoparticles.
What is the capacity of MgH2 with 10 wt% Ni/TiO2 during isothermal dehydrogenation?
6.1 wt%.
What barriers does MgH2 face for practical use?
Challenges in thermodynamics and kinetics.
What method was used to synthesize nanocrystalline Ni@C and Co@C?
By calcining a mixture of LiOH·H2O, benzimidazole, and Ni(NO3)2·6H2O/Co(NO3)2·6H2O at low temperatures.
What was the hydrogen absorption capacity of the MgH2-5 wt% Ni@C composite at 150 °C?
5.0 wt% H2 within 40 seconds.
What factors influence hydrogen sorption kinetics in Mg nanocrystallines?
Defect sites in the Mg nanocrystallines.
What is the advantage of using carbon as a supporting material for metal nanoparticles?
It helps overcome agglomeration and growth during hydrogen sorption, increasing catalytic efficiency.
What method was used to obtain the Mg-TiH nanocomposite that quickly absorbed hydrogen?
Hydrogen plasma-metal reaction (HPMR) method.
What was the desorption rate of the mesoporous NiO-doped MgH2 compared to pure MgH2?
7 times faster.
What was the hydrogen storage capacity of MgH2 nanoparticles synthesized from di-n-butylmagnesium?
6.8 wt%.
How can nanotechnology improve MgH2 performance?
By employing nanocatalysts and reducing particle size to nanoscale.
What is the average size of Ni particles in the carbon-supported nano-Ni (Ni@C) composite?
About 7.5 nm.
What was the particle size range for Co@C and Ni@C nanoparticles obtained from MOFs?
8-10 nm for Co@C and 12-16 nm for Ni@C.
What temperature was required to release 5 wt% H2 from the Ti-coated Mg composite?
250 °C within 15 minutes.
What is the significance of the TiO2@C catalyst in hydrogen storage?
It reduces the dehydrogenation onset temperature to 205 °C and releases 6.7 wt% H2 within 7 minutes at 300 °C.
What effect does replacing Li with Na or K have on Mg nanoparticles?
It results in the formation of NaMgH3 and KMgH3 perovskite structures, enhancing cycle stability.
What is the hydrogen absorption and desorption performance of the Ni-doped TiO2 nanocatalyst?
Absorbed 4.5 wt% H2 at 50 °C and desorbed 5.24 wt% H2 in 1800 seconds at 250 °C.
What role does Ni play in the NiTiO3 enhanced MgH2 system?
Ni provides hydrogen diffusion channels and heterogeneous nucleation sites for easy H2 release.
What is the gravimetric hydrogen capacity of MgH2?
7.6 wt%.
What is the hydrogen absorption capacity of 5 wt% Ni-MOF-74 at 150 °C within 30 seconds?
6.2 wt% H2.
Which composite showed higher catalytic activity for MgH2: carbon-supported nano nickel or a physical mixture of nickel and carbon?
Carbon-supported nano nickel particles.
What is the particle size limit that ball milling can typically achieve for MgH2?
Around 300 nm.
What is the performance of the Mg@Ti@Ni composite compared to Mg@Ti?
Mg@Ti@Ni shows better hydrogen storage performance than Mg@Ti.
How does the addition of TiO2 nanosheets affect the kinetic performance of MgH2?
It allows for the release of 6.0 wt% hydrogen within 3.2 minutes at 260 °C.
What is the capacity of MgH2 with 10 wt% TiVO3.5 during isothermal hydrogenation?
6.5 wt%.
How much hydrogen could the MgH2 composite catalyzed with 5 wt% Ni@C desorb within 10 minutes at 300 °C?
6.4 wt% H2.
What is the target gravimetric hydrogen density set by the U.S. Department of Energy?
6.5 wt%.
What is the reversible hydrogen storage capacity of the Ti-coated Mg composite?
6.7 wt%.
What effect does nanostructuring have on MgH2?
It increases specific surface areas and provides more active sites for hydrogen absorption and dissociation.
What is the conventional method for reducing the particle size of MgH2?
Mechanical milling.
What is the hydrogen absorption capacity of a MgH2-0.1TiH2 nanocomposite?
It can absorb hydrogen at room temperature and maintain capacity over 80 cycles.
What is the effect of particle size below 10 nm on MgH2?
It can lead to thermodynamic destabilization of MgH2.
How quickly could the synthesized MgH2 release hydrogen at 300 °C?
In 15 minutes.
What are the two main strategies discussed for enhancing MgH2 performance?
Using nanocatalysts and nanostructuring methods.
What is a significant challenge for onboard hydrogen storage?
Safe, efficient, and economical hydrogen storage.
At what temperature does the MgH2 composite with 10 wt% nano-ZrMn2 start releasing H2?
181.9 °C.
What is the hydrogen desorption capacity of the MgH2 composite at 300 °C in 5 minutes?
6.7 wt% hydrogen.
What did density functional theory calculations reveal about ZrMn2's effect on MgH2?
ZrMn2 elongated the Mg-H bond length and weakened the Mg-H bond, enhancing kinetics.
What was the diameter of the well-defined Mg nano fibers synthesized?
40 nm.
What is the onset temperature for non-isothermal dehydrogenation of MgH2 with 10 wt% Ni?
250 °C.
What is the cycle stability of the Fe3O4@GS-catalyzed MgH2 after 25 cycles?
0.38 wt% capacity loss.
What effect does the synthetic medium have on the morphology of MgH2?
It varies the size and shape of the nanoparticles.
What advantage does the MgH2-Co/Pd@B-CNTs composite have in terms of hydrogen absorption?
It can absorb 6.68 wt% H2 within 10 seconds at 250 °C.
What are the current hydrogen storage methods mentioned?
High-pressure gaseous storage, cryogenic liquid storage, and solid-state storage.
How much hydrogen can the composite absorb at room temperature within 10 hours?
2.7 wt% H2.
What was the hydrogen absorption rate of MgH2 doped with 0.2 mol% Nb2O5 at 300 °C?
6.9 wt% H2 within 60 seconds.
What unique structure does Ti3C2 MXene have, and how does it affect MgH2?
It has a unique layer structure that enhances catalytic activity, lowering the onset dehydrogenation temperature to 185 °C.
What was the hydrogen desorption performance of the 10 wt% TiVO3.5-containing MgH2 at 250 °C?
Desorbed 5.0 wt% H2 in 10 minutes.
What was observed about the hydrogenolysis temperatures and their effect on MgH2 morphology?
Higher temperatures led to different particle shapes and sizes, affecting desorption performance.
What method was used to prepare the Ni/Gn-MgH2 composite?
Hydriding combustion synthesis (HCS) method.
What is the effect of the Ni@C nanorod structure on MgH2?
It restricts the growth and agglomeration of Ni nanoparticles and MgH2 grains, enhancing catalytic effect.
What special species formed in situ improve hydrogen absorption kinetics in Nb-based compounds?
NbHx, NbO, and MgNb x O y.
What was the hydrogen absorption capacity of the Mg-Nb nanocomposite at 100 °C?
3.4 wt% H2.
What role do dispersive Ni particles play in the Ni/Gn-MgH2 composite?
They act as nucleation sites to facilitate the nucleation of Mg on graphene nanoplate.
What is the significance of using multiwall carbon nanotubes (MWCNTs) in catalysts?
They support metal composites like Pd/MWCNTs and enhance hydrogen absorption and desorption kinetics.
What effect does the size and disorder of NbHx nanoparticles have on catalytic activity?
Smaller and more disordered NbHx nanoparticles exhibit higher catalytic activity.
How much hydrogen does the MgH2-5 wt% Ni@rGO composite desorb in 10 minutes at 300 °C?
6.0 wt% hydrogen.
What effect does TiN@rGO have on the dehydrogenation onset temperature of MgH2?
It reduces the onset temperature to 167 °C from 307 °C.
What is the hydrogen storage capacity of MgH2 with 4 mol% Ni NFs during isothermal hydrogenation?
7.0 wt%.
What is the role of catalyst doping in MgH2 systems?
It effectively relieves the de-/rehydrogenation energy barrier.
What is the peak temperature for MgH2 with 6 wt% NiTiO3 during non-isothermal dehydrogenation?
261 °C.
What was the performance of the MgH2 plus Ni-VOx/AC composite in hydrogen absorption?
It absorbed 6.2 wt% H2 within just 1 minute at 150 °C.
What is the effect of doping MgH2 with Nb on its hydrogen storage properties?
It shows a capacity of 7.0 wt% at 237 °C.
What transformation occurs to Ni during the reaction with Mg?
Ni is transformed into Mg2Ni.
What was the hydrogen absorption capacity of the Mg95-(Pd3Ni3/MWCNTs4)5 composite at 100 °C?
6.44 wt% H2 within 100 seconds.
What unique structure was created by using bamboo-shaped carbon nanotubes (B-CNTs)?
Co/Pd nanoparticles were dispersed, with Pd nanoparticles attached to the walls and Co nanoparticles at the tips.
What is magnesium hydride (MgH2) considered for?
One of the most promising candidates for solid-state hydrogen storage.
What are the advantages of MgH2 as a hydrogen storage medium?
High hydrogen capacity, excellent reversibility, and low cost.
