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Location-dependent effect of nickel on hydrogen dissociation and diffusion on Mg (0001) surface Insights into hydrogen storage material design

Abstract

Density functional theory (DFT) calculations have been performed to investigate the hydrogen dissociation and diffusion on Mg (0001) surface with Ni incorporating at various locations. The results show that Ni atom is preferentially located inside Mg matrix rather than in/over the topmost surface. Further calculations reveal that Ni atom locating in/over the topmost Mg (0001) surface exhibits excellent catalytic effect on hydrogen dissociation with an energy barrier of less than 0.05 eV. In these cases, the rate-limiting step has been converted from hydrogen dissociation to surface diffusion. In contrast, Ni doping inside Mg bulk not only does little help to hydrogen dissociation but also exhibits detrimental effect on hydrogen diffusion. Therefore, it is crucial to stabilize the Ni atom on the surface or in the topmost layer of Mg (0001) surface to maintain its catalytic effect. For all the case of Ni-incorporated Mg (0001) surfaces, the hydrogen atom prefers firstly immigrate along the surface and then penetrate into the bulk. It is expected that the theoretical findings in the present study could offer fundamental guidance to future designing on efficient Mg-based hydrogen storage materials.

Funding source: National Natural Science Foundation of China (Grant Nos. U1610103, 21805169 and 21978156), Shandong Provincial Natural Science Foundation, China (Grant No. ZR2018BB069), and Project of Shandong Province Higher Educational Young Innovative Talent Introduction and Cultivation Team (Hydrogen energy chemistry innovation team).
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/content/journal2056
2021-04-15
2021-07-24
http://instance.metastore.ingenta.com/content/journal2056
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