Heterojunction synergistic catalysis of MXene-supported PrF_(3)nanosheets for the efficient hydrogen storage of AlH_(3)

Aluminum hydride is a promising chemical hydrogen storage material that can achieve dehydrogenation under mild conditions as well as high hydrogen storage capacity.However,designing an efficient and cost-effective catalyst,especially a synergistic catalyst,for realizing low-temperature and high-efficiency hydrogen supply remains challenging.In this study,the heterojunction synergistic catalyst of Ti_(3)C_(2)supported PrF_(3)nanosheets considerably improved the dehydrogenation kinetics of AlH_(3)at low temperatures and maintained a high hydrogen storage capacity.In the synergistic catalyst,Pr produced a synergistic coupling interaction through its unique electronic structure.The sandwich structure with close contact between the two phases enhanced the interaction between species and the synergistic effect.The initial dehydrogenation temperature of the composite is reduced to 70.2℃,and the dehydrogenation capacity is 8.6 wt.%at 120℃ in 90 min under the kinetic test,which reached 93%of the theoretical hydrogen storage capacity.The catalyst considerably reduced the activation energy of the dehydrogenation reaction.Furthermore,the multielectron pairs on the surface of the catalyst promoted electron transfer and accelerated the reaction.

Dehydrogenation behavior and mechanism of LiAlH_(4) adding nano-CeO_(2)with different morphologies

Complex hydride LiAlH_(4),as a hydrogen storage material,possesses high theoretical hydrogen storage capacity(10.5 wt.%).However,highly efficient additives are urgently required to modify its thermal stability and sluggish kinetics.Some additives exhibit unique morphology-dependent characteristics.Herein,the efficient rare earth oxide nano-CeO_(2)additives with different morphologies(nanoparticles,nanocubes,and nanorods)are prepared by the hydrothermal method,and the intrinsic properties are characterized.The three different morphologies of nano-CeO_(2),which are different in the Ce^(3+)content and specific surface area,are added to LiAlH_(4)to improve the dehydrogenation behavior.The LiAlH_(4)-CeO_(2)-nanorod composite exhibits the optimal dehydrogenation behavior,which begins to desorb hydrogen at 76.6℃ with a hydrogen capacity of 7.17 wt.%,and 3.83 wt.%hydrogen is desorbed within 30 min at 140℃.The dehydrogenation process of the composites demonstrates that hydrogen release is facilitated by the in-situ formed CeH_(2).73 and the facile transition between the oxidation states of Ce^(4+)and Ce^(3+).Combined with density functional theory calculations,the addition of nano-CeO_(2)can weaken the Al-H bond and accelerate the decomposition of[AlH_(4)]^(4-)tetrahedron,which is consistent with the reduction of the decomposition activation energy.

Multidimensional regulation of Ti-Zr-Cr-Mn hydrogen storage alloys via Y partial substitution

High density and safe storage of hydrogen are the preconditions for the large-scale application of hydrogen energy.Herein,the hydrogen storage properties of Ti_(0.6)Zr_(0.4)Cr_(0.6)Mn_(1.4) alloys are systematically studied by introducing Y element instead of Ti element through vacuum arc melting.After the partial substitution of Y,a second phase of rare earth oxide is added in addition to the main suction hydrogen phase,C14 Laves phase.Thanks to the unique properties of rare earth elements,the partial substitution of Y can not only improve the activation properties and plateau pressure of the alloys,but also increase the effective hydrogen storage capacity of the alloys.The comprehensive properties of hydrogen storage alloys are improved by multidimensional regulation of rare earth elements.Among them,Ti_(0.552)Y_(0.048)Zr_(0.4)Cr_(0.6)Mn_(1.4) has the best comprehensive performance.The alloy can absorb hydrogen without activation at room temperature and 5 MPa,with a maximum hydrogen storage capacity of 1.98 wt.%.At the same time,it reduces the stability of the hydride and the enthalpy change value,making it easier to release hydrogen.Through theoretical analysis and first-principle simulation,the results show that the substitution of Y element reduces the migration energy barrier of hydrogen and the structural stability of the system,which is conducive to hydrogen evolution.The alloy has superior durability compared to the original alloy,and the capacity retention rate was 96.79%after 100 hydrogen absorption/desorption cycles.