Hydrogen Storage Interface, Strain, Material Design

Hydrogen Storage 105

We have studied hydrogen adsorption on the Mg(0001) surface under biaxial strain, using density-functional theory calculations. A phase diagram is obtained for an intuitive sense of how the strain and hydrogen chemical potential affect the structural stabilities of Mg-H system.

During the hydrogenation, the H−Mg−H trilayer and MgH2 bulk-like structures could be coexisting, where the strain is able to modulate their relative stabilities. Experimental investigations confirmed a remarkable decrease in the hydrogen absorption temperature in the Mg (1013), down to 392 K from 592 K of the Mg film (0001).The ab initio calculations reveal that non-close-packed Mg(1013) slab is advantageousfor hydrogen sorption, attributing to the tilted close-packed-planes in the Mg(1013) slab.

We report a simple method to induce a novel symbiotic CeH2.73/CeO2 catalyst in Mg-based hydrides and reveal a spontaneous hydrogen release effect at the CeH2.73/CeO2 interface, which leads to dramatic increase of catalysis than either sole CeH2.73 or CeO2 catalyst. The ab-initio calculations show significant reduction of the formation energy of VH (hydrogen vacancy)in the CeH2.73/CeO2 boundary region in comparison to those in the bulk MgH2 and CeH2.73. We demonstrate that the outstanding catalyticactivity can be attributed tothe spontaneous hydrogen release effect at the CeH2.73/CeO2 interface.

Transition-metal (TM) dispersed nanostructures have been approved to be efficient for the hydrogen storage. The high capacity hydrogen storage is based on the condition that TM atoms coated on the surface will remain isolated, While TM atoms would form clusters on the surface because the binding energies between TM and substrate were found to be much lower than that of bulk TM structures. With carbon substitution of nitrogen, Sc, V, Cr, and Mn atoms were energetically favorable to be dispersed on the BN nanostructures without clustering. Ti decorated defective graphene under 15% strain could be considered as an ideal media of hydrogen storage, in which the desorption temperature of H2 is expected to be ~300 K at 0.5 atm. Our finding proposes the controllable uptake of H2 by the biaxial strain of substrate, which could facilitate the usage of hydrogen fuel.

Referrence

1. J. Phys. Chem. C , 116, 14943(2012).
2. Nano Energy 9, 80(2014).
3. J. Phys. D: 47, 115305(2014).
4. Scientific Reports 5, 10776(2015).
5. Phys. Rev. B 86, 045459(2012).
6. Int. J. Hydrogen Energy 37, 309(2012).
7. Int. J. Hydrogen Energy 40, 12063(2015).
8. Int. J. of Hydrogen Energy 41, 11275(2016).