A group of researchers has identified the key stumbling block of a common solid-state hydrogen material, paving the way for future design guidelines and widespread commercial use.
Details of their findings were published in Journal of materials chemistry Awhere the article was featured as a cover story.
Hydrogen will play a significant role in fueling our future. It is abundant and produces no harmful emissions when burned. But storing and transporting hydrogen is both expensive and risky.
Currently, hydrogen is stored by three methods: high-pressure gaseous hydrogen storage, low-temperature liquid hydrogen storage, and solid-state hydrogen storage. Among solid-state hydrogen storage, solid-state materials are generally the safest and offer the highest hydrogen storage density.
Metal hydrides have long been explored for their high hydrogen storage potential and low cost. As these metals come into contact with hydrogen gas, the hydrogen is absorbed to the surface. The additional energy input causes hydrogen atoms to find their way into the crystal lattice of the metal until the metal becomes saturated with hydrogen. From there, the material can absorb and desorb hydrogen in larger quantities.
Magnesium hydride (MgH2) showed immense promise for superior hydrogen storage capacity. However, a high temperature is required for MgH2 to decompose and produce hydrogen. Moreover, the material’s complex hydrogen migration and desorption, resulting in slow dehydrogenation kinetics, have hindered its commercial application.
For decades, scientists have debated why dehydrogenation into MgH2 it is so difficult. But now, the research group has discovered an answer.
Using calculations based on spin-polarized density functional theory with van der Waals corrections, they discovered a “burst effect” during MgH2its dehydrogenation. The initial dehydrogenation barriers were measured to be 2.52 and 2.53 eV, while the subsequent reaction barriers were 0.12–1.51 eV.
The group performed further analysis of the bonds with the crystal orbital Hamiltonian population method, where they confirmed that the strength of the magnesium hydride bond decreased as the dehydrogenation process continued.
“Hydrogen migration and hydrogen desorption are much easier following the initial explosion effect,” points out Hao Li, associate professor at Tohoku University’s Advanced Materials Research Institute (WPI-AIMR) and corresponding author of the paper. “Structural engineering adjustments that promote this desorption process could be the key to facilitating hydrogen desorption of MgH.2.”
Li and his colleagues demonstrated that the hydrogen vacancies maintained a high degree of electronic localization when the first layer of atomic hydrogen exists. Analyzes of the kinetic characteristics of MgH2 after surface dehydrogenation, performed by ab initio molecular dynamics simulations, also provided additional evidence.
“Our findings provide a theoretical basis for MgH2its dehydrogenation kinetics, providing important guidelines for MgH modification2hydrogen-based storage materials,” adds Li.
Shuai Dong et al., “Explosion Effect” of Hydrogen Desorption in MgH2 Dehydrogenation, Journal of materials chemistry A (2022). DOI: 10.1039/D2TA06458H
Provided by Tohoku University
Citation: Hydrogen Storage Material Key Restriction Identified (2023, January 13) Retrieved January 15, 2023 from https://phys.org/news/2023-01-hydrogen-storage-material-key-restriction.html
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