With the depletion of fossil fuels and global warming, there is an urgent need to seek green, clean, and efficient energy resources. Against this backdrop, hydrogen is considered a potential candidate for replacing fossil fuels due to its high energy density and environmentally friendly nature. To realize the development of a hydrogen economy, safe and efficient hydrogen storage technologies are crucial. Compared to traditional compressed hydrogen and cryogenic liquid hydrogen storage technologies, solid-state hydrogen storage is considered a safer and more efficient method. Magnesium hydride (MgH 2 ), as one of the most promising solid-state hydrogen storage materials, has attracted attention due to its abundant elemental resources, high hydrogen storage capacity, good reversibility, and non-toxicity. However, the relatively high operating temperature of MgH 2 limits its large-scale commercial application in vehicular or stationary hydrogen storage.
Introducing transition metal-based catalysts with unique three-dimensional electronic structures is considered an effective method to improve the kinetics of MgH 2 . Vanadium (V) and its oxides are often used as catalysts for MgH 2 due to their multivalence and high catalytic activity. However, due to the high ductility of metallic vanadium and relatively low activity, vanadium-based oxides have broader application prospects. Layered V 2 O 5 with a layered structure is one of the promising catalysts to enhance the hydrogen storage performance of MgH 2 /Mg, but limited catalytic capacity due to insufficient contact between V 2 O 5 and MgH 2 .
To address this issue, Dr. Jianxin Zou's team at Shanghai Jiao Tong University employed a solvothermal method followed by subsequent hydrogenation to prepare ultra-thin hydrogenated V 2 O 5 nanosheets with abundant oxygen vacancies and used them as catalysts to improve the hydrogen storage performance of MgH 2 . The MgH 2 -H-V 2 O5 composite material exhibits excellent hydrogen storage performance, including a lower desorption temperature (T onset = 185°C), rapid desorption kinetics (E a = 84.55 kJ mol −1 H 2 for desorption), and long-term cyclic stability (capacity retention of up to 99% after 100 cycles). Particularly, the MgH 2 -H-V 2 O 5 composite material shows outstanding hydrogen absorption performance at room temperature, with a hydrogen absorption capacity of 2.38 wt% within 60 minutes at 30°C.
The H-V 2 O 5 nanosheets synthesized by Dr. Zou's team possess a unique two-dimensional structure and abundant oxygen vacancies, enabling the in-situ formation of V/VH 2 during the reaction process, all of which contribute to enhancing the hydrogen storage performance of MgH 2 . By using a solvothermal method to create a distinct anisotropic layered structure, a highly exposed surface is formed, thereby providing more active sites and pathways for hydrogen/electron diffusion, thus improving hydrogen storage performance. Moreover, crucially, the presence of oxygen vacancies accelerates electron transfer, stimulating the "hydrogen pump" effect of VH 2 /V, facilitating the dehydrogenation of VH 2 and MgH 2 , and reducing the energy barriers for hydrogen dissociation and recombination. Introducing oxygen vacancy defect engineering into the catalyst thus opens up a new avenue for enhancing the cyclic stability and kinetic performance of MgH 2 .
Nature
Experimental study
Boosting Hydrogen Storage Performance of MgH2 by Oxygen Vacancy-Rich H-V2O5 Nanosheet as an Excited H-Pump
21-Mar-2024