Magnesium Oxide

Magnesium hydride has long been touted for its potential to store large amounts of hydrogen, something essential if hydrogen is to play a role in powering a sustainable future. Yet, sluggish dehydrogenation kinetics and the high temperature required to decompose and produce hydrogen from the material have stymied its use. Now, researchers have identified why this is so, paving the way for future design guidelines and widespread commercial use. 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 the Journal of Materials Chemistry A, where the article was featured as a Front Cover Article. Hydrogen will play a significant role in powering our future. It's abundant and produces no harmful emissions when burned. But the storage and transportation of hydrogen is both costly 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 provide the most hydrogen storage density. Metal hydrides have long been explored for their large hydrogen storage potentiality and their low cost. As these metals come into contact with gaseous hydrogen, hydrogen gets absorbed onto the surface. Further energy input leads to hydrogen atoms finding their way into the metal's crystal lattices until the metal becomes saturated with hydrogen. From there, the material can absorb and desorb hydrogen in larger amounts. Magnesium hydride (MgH2) has shown immense promise for superior hydrogen storage capacity. However, a high temperature is necessary for MgH2 to decompose and produce hydrogen. Furthermore, the material's complex hydrogen migration and desorption, which result in sluggish dehydrogenation kinetics, have stymied its commercial application. For decades, scientists have debated why dehydrogenation within MgH2 is so difficult. But now, the research group has uncovered an answer. Using calculations based on spin-polarized density functional theory with van der Waals corrections, they unearthed a 'burst effect' during MgH2's dehydrogenation. The initial dehydrogenation barriers measured at 2.52 and 2.53 eV, whereas subsequent reaction barriers were 0.12-1.51 eV. The group carried out further bond analysis with the crystal orbital Hamilton population method, where they confirmed the magnesium-hydride bond strength decreased as the dehydrogenation process continued. "Hydrogen migration and hydrogen desorption is much easier following the initial burst effect," points out Hao Li, associate professor at Tohoku University's Advanced Institute for Materials Research (WPI-AIMR) and corresponding author of the paper. "Structural engineering tweaks that promote this desorption process could be the key to facilitating the hydrogen desorption of MgH2." Li and his colleagues demonstrated that hydrogen vacancies maintained a high degree of electronic localization when the first layer of atomic hydrogen exists. Analyses 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 the MgH2's dehydrogenation kinetics, providing important guidelines for modifying MgH2-based hydrogen storage materials," adds Li.

An interdisciplinary team of researchers has developed a potential breakthrough in green aviation: a recipe for a net-zero fuel for planes that will pull carbon dioxide (CO2) out of the air. An interdisciplinary team of researchers at Worcester Polytechnic Institute (WPI) has developed a potential breakthrough in green aviation: a recipe for a net-zero fuel for planes that will pull carbon dioxide (CO2) out of the air. The research, which used sophisticated computational modeling and analysis, was recently published in the journal Fuel. Led by Jagan Jayachandran, assistant professor of aerospace engineering, and Adam Powell, associate professor of mechanical and materials engineering, the work helps address an urgent climate change problem. Aviation accounts for approximately 2.5% of all global greenhouse emissions, according to the International Council on Clean Transportation (ICCT), and that number is only expected to increase. "As aviation continues to grow, so will the industry's emissions, says Powell. "We need to think out of the box and look at sustainable materials that will contribute to a long-term solution toward reducing the transportation sector's carbon footprint." Through modeling and computation analysis, Jayachandran and Powell developed a formula for a fuel that consists of magnesium, a mineral that is found all over the globe, most abundantly in the world's oceans. A slurry of magnesium hydride -- a chemical compound made up of magnesium and hydrogen -- mixed with hydrocarbon fuel would burn to produce CO2, water vapor and magnesium oxide (MgO) nanoparticles. The magnesium hydride fuel would also give planes the range for long-haul flights -- e.g., from Boston to Tokyo -- something that has been a challenge for other sustainable aviation fuels to provide. That longer range is achieved, in part, due to the chemical properties of the slurry -- a lower volume of it is needed for combustion than a typical aviation fuel. "We found this fuel would have up to 8% more range than other today's jet fuel, and more than two to three times longer range than liquid hydrogen or ammonia which other researchers have proposed as sustainable fuels," said Jayachandran. The Department of Energy describes a sustainable aviation fuel as a "biofuel used to power aircraft that has similar properties to conventional jet fuel but with a smaller carbon footprint." These biofuels have been made from resources including corn grain, algae, forestry, and agricultural residues, among others. Using a biofuel as the hydrocarbon in this slurry with magnesium hydride could potentially lead to net negative emissions. The research was supported by a WPI TRIAD Seed Grant, a university award intended to encourage and promote interdisciplinary collaboration and innovation. Jayachandran and Powell plan to further their research through physical experiments with samples of the fuel, and are also pursuing potential funding from a federal agency. In addition, they hope this work can inspire others and contribute to a more sustainable world. Noting the promise of research to mitigate emissions and other climate threats, Powell said, "we hope our work, which opens up a new category of sustainable aviation fuel will spark the imagination of other researchers. The sky's the limit."