Du A J, Smith Sean C, Yao X D, Sun C H, Li L, Lu G Q
Centre for Computational Molecular Science, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, QLD 4072, Australia.
J Nanosci Nanotechnol. 2009 Jul;9(7):4388-91. doi: 10.1166/jnn.2009.m65.
Recent experiments [F. E. Pinkerton, M. S. Meyer, G. P. Meisner, M. P. Balogh, and J. J. Vajo, J. Phys. Chem. C 111, 12881 (2007) and J. J. Vajo and G. L. Olson, Scripta Mater. 56, 829 (2007)] demonstrated that the recycling of hydrogen in the coupled LiBH4/MgH2 system is fully reversible. The rehydrogenation of MgB2 is an important step toward the reversibility. By using ab initio density functional theory calculations, we found that the activation barrier for the dissociation of H2 are 0.49 and 0.58 eV for the B and Mg-terminated MgB2(0001) surface, respectively. This implies that the dissociation kinetics of H2 on a MgB2(0001) surface should be greatly improved compared to that in pure Mg materials. Additionally, the diffusion of dissociated H atom on the Mg-terminated MgB2(0001) surface is almost barrier-less. Our results shed light on the experimentally-observed reversibility and improved kinetics for the coupled LiBH4/MgH2 system.
近期的实验[F. E. 平克顿、M. S. 迈耶、G. P. 迈斯纳、M. P. 巴洛赫和J. J. 瓦霍，《物理化学杂志C》111, 12881 (2007) 以及J. J. 瓦霍和G. L. 奥尔森，《材料科学进展》56, 829 (2007)]表明，在耦合的LiBH4/MgH2体系中氢的循环是完全可逆的。MgB2的再氢化是实现可逆性的重要一步。通过使用从头算密度泛函理论计算，我们发现对于B端和Mg端的MgB2(0001)表面，H2解离的活化能垒分别为0.49和0.58 eV。这意味着与纯Mg材料相比，H2在MgB2(0001)表面的解离动力学应该会大大改善。此外，解离的H原子在Mg端的MgB2(0001)表面上的扩散几乎没有能垒。我们的结果为耦合LiBH4/MgH2体系中实验观察到的可逆性和改善的动力学提供了线索。
