CAREER: Improving Hydrogen Storage with van der Waals Density Functional Theory

Wake Forest University, Winston Salem NC

Investigators

Abstract

TECHNICAL SUMMARY This CAREER award supports an integrated research and education plan related to hydrogen storage and alternative energy. The research plan addresses the hydrogen-storage problem, a critical barrier to a hydrogen economy and an urgently needed alternative fuel. Magnesium borohydride Mg(BH4)2, ammonia borane NH3BH3, and methane-based material (H2)4CH4 show great potential, but they release or store hydrogen only at impractical high or low temperatures. To resolve this problem, the research plan includes the following objectives: (i) lowering the hydrogen desorption temperature in Mg(BH4)2 by destabilization through doping; (ii) lowering the desorption temperature in NH3BH3 by substitutions in the hydridic group to lower the activation barrier; and (iii) determining whether alkanes longer than the methane in (H2)4CH4 can be stable at higher temperatures. While these materials are different in nature, reaching from chemisorption to physisorption of hydrogen, they are all influenced by van der Waals interactions. A novel density functional theory approach that includes van der Waals interactions fully self-consistently will be used to calculate temperature-dependent reaction enthalpies for the hydrogen release and barriers to hydrogen desorption using nudged elastic band calculations. Throughout the project, computational and theoretical efforts will be coordinated with experiments to determine materials' properties and significantly advance research on hydrogen as an alternative fuel. Computational tools will also be greatly improved during the project, since a key methodological goal is to combine van der Waals density functional theory with Car-Parrinello molecular dynamics to evaluate thermodynamic stabilities. This will result in a new tool for modeling a wide range of materials from water to DNA and be made available to the larger scientific community through a general public license. This CAREER award also supports the PI's educational and outreach plans of addressing the lack of scientific literacy in a highly diverse region facing economic and educational challenges, and inadequate mentoring in academic science. The objectives are (i) to work with the local science museum and schools to create an "Energy Zone" that will include a display, demonstration, teaching module, and informal talks at the Science Café for the general public about alternative energy and hydrogen as fuel; and (ii) to develop an interdepartmental mentoring program for graduate students and postdocs in the sciences to improve their research skills and transition to independent careers. NONTECHNICAL SUMMARY This CAREER award supports an integrated research and education plan related to hydrogen storage and alternative energy. As a tasteless, colorless, odorless, and nontoxic molecule, hydrogen has been identified as an ideal fuel that can be produced renewably from a variety of sources. It is the most abundant element on Earth, and all nations have access to it. Its combustion reaction with pure oxygen is perfectly clean, creating neither air pollutants nor greenhouse gases. In practical terms, the energy content of 1 kg of hydrogen corresponds to 3 kg of gasoline, whereas 3 kg of gasoline also produce 9 kg of undesirable greenhouse gas. Although hydrogen is the ideal fuel, the reason why it is not widely used is that there are problems related to hydrogen production, storage, and use. This research program will address the hydrogen-storage problem. The primary goal of the project is to investigate and manipulate properties of several materials, such as magnesium borohydride, ammonia borane, and methane-based materials known as H4-alkanes which show great potential for hydrogen storage. The focus of the project will be to stabilize such materials at ambient pressures and temperatures by utilizing novel theoretical and computational methods. These computational efforts will be coordinated with experimental studies to determine the materials' properties and significantly advance research on hydrogen as an alternative fuel. The project will also result in a new computational tool for modeling a wide range of materials which display a particular kind of bonding that makes straightforward applications of state-of-the-art computational techniques challenging. The resulting computational tool will be made available to the larger scientific community through a general public license. This CAREER award also supports the PI's educational and outreach plans of addressing the lack of scientific literacy in a highly diverse region facing economic and educational challenges, and inadequate mentoring in academic science. The objectives are (i) to work with the local science museum and schools to create an "Energy Zone" that will include a display, demonstration, teaching module, and informal talks at the Science Café for the general public about alternative energy and hydrogen as fuel; and (ii) to develop an interdepartmental mentoring program for graduate students and postdocs in the sciences to improve their research skills and transition to independent careers.