Geometric structures and hydrogen storage properties of M2B7 (M=Be,Mg, Ca) clusters |
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| Affiliation: | 1. North University of China, School of Materials Science and Engineering, Taiyuan, 030051, Shanxi, China;2. Xinzhou Teachers University, Department of Chemistry, Xinzhou, 034000, Shanxi, China;3. Shanxi College of Technology, School of Materials Industry, Shuozhou, 036000, Shanxi, China;1. School of Energy and Power, Jiangsu University of Science and Technology, Zhenjiang 212100, China;2. School of Economics and Management, Jiangsu University of Science and Technology, Zhenjiang 212100, China;3. School of Energy and Power Engineering, Shandong University, Jinan 250061, China;4. National Research Ogarev Mordovia State University, Saransk 430005, Russian Federation;1. School of Energy and Mechanical Engineering, Jiangxi University of Science and Technology, Nanchang, 330013, China;2. School of Physics and Electronics, Hunan University, Changsha, 410082, China;3. School of Software Engineering, Jiangxi University of Science and Technology, Nanchang, 330013, China;1. Waikato Centre for Advanced Materials and Manufacturing, School of Engineering, University of Waikato, Hamilton, 3240, New Zealand;2. School of Science, University of Waikato, Hamilton, 3240, New Zealand;3. Key Laboratory of Advanced Metals and Materials of Inner Mongolia, School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou, 014010, China;4. School of Materials Science and Engineering, Shenyang University of Technology, Shenyang, 110870, PR China;1. Institute of Energy and Power Engineering, Zhejiang University of Technology, Hangzhou 310027, China;2. Zhejiang Carbon Neutral Innovation Institute, Hangzhou 310000, China;3. Interdiscipilinary Research Center for Refining & Advanced Chemicals, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia;4. Faculty of Science and Engineering, Kasetsart University Chalermphrakiat Sakon Nakhon Province Campus, Sakon Nakhon 47000, Thailand;5. Center of Excellence in Environmental Catalysis and Adsorption, Faculty of Engineering, Thammasat University, Pathumthani 12120, Thailand;1. Key Laboratory of Magnetic Molecules & Magnetic Information Materials Ministry of Education, and the School of Chemical and Material Science, Shanxi Normal University, Taiyuan, 030031, China |
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| Abstract: | Based on the density functional theory, we investigate the electronic properties of the clusters M2B7 (M = Be, Mg, Ca) and their hydrogen storage properties systematically in this paper. Extensive global search results show that the global minimal structures of the three systems (Be2B7, Mg2B7 and Ca2B7) are heptagonal biconical structure, and the two alkaline earth metals are located at the top of the biconical. Chemical bonding analyses show that M2B7 clusters have 6σ and 6π delocalized electrons, which are doubly aromatic. At the wB97XD level, the three systems have good hydrogen storage capabilities. The hydrogen storage density of Be2B7 is as high as 23.03 wt%, while Mg2B7 and Ca2B7 also far exceed the hydrogen storage target set by the U.S. Department of Energy in 2017. Their average adsorption energies of H2 molecules all ranged from 0.1 eV/H2 to 0.48 eV/H2, which is fall in between physisorption and chemisorption. Extensive Born Oppenheimer molecular dynamics (BOMD) simulations show that the H2 molecules of the three systems can be completely released at a certain temperature. Therefore, M2B7 systems can achieve reversible adsorption of H2 molecules at normal temperature and pressure. It can be seen that the B7 clusters modified by alkaline earth metals may become a promising new nano-hydrogen storage material. |
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| Keywords: | Density functional theory Hydrogen storage density Reversible adsorption Hydrogen storage material |
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