Progress on first-principles-based materials design for hydrogen storage

Abstract

This article briefly summarizes the research activities in the field of hydrogen storage in sorbent materials and reports our recent works and future directions for the design of such materials. Distinct features of sorption-based hydrogen storage methods are described compared with metal hydrides and complex chemical hydrides. We classify the studies of hydrogen sorbent materials in terms of two key technical issues: (i) constructing stable framework structures with high porosity, and (ii) increasing the binding affinity of hydrogen molecules to surfaces beyond the usual van der Waals interaction. The recent development of reticular chemistry is summarized as a means for addressing the first issue. Theoretical studies focus mainly on the second issue and can be grouped into three classes according to the underlying interaction mechanism: electrostatic interactions based on alkaline cations, Kubas interactions with open transition metals, and orbital interactions involving Ca and other nontransitional metals. Hierarchical computational methods to enable the theoretical predictions are explained, from ab initio studies to molecular dynamics simulations using force field parameters. We also discuss the actual delivery amount of stored hydrogen, which depends on the charging and discharging conditions. The usefulness and practical significance of the hydrogen spillover mechanism in increasing the storage capacity are presented as well.

Fig. 1.

Atomic configurations of 4H₂ molecules attached to the backbone structure. The backbone is (A) Fe-decorated, OH-functionalized terphenyl dicarboxylate (TPDC), and (B) V-decorated, OH-functionalized TPDC, respectively, where TPDC is the linker part of the IRMOF16. The blue, gray, red, green, and orange balls stand for hydrogen, carbon, oxygen, iron, and vanadium atoms, respectively.

Fig. 2.

Geometries of Ca atom with (A) attached and (B) far separated four hydrogen molecules. (C) Optimized geometry and (D) molecular orbital levels of the Ca adsorbed anthracene structure. (E) Same structure as in C, with four adsorbed hydrogen molecules. The isosurface plot of each HOMO state is also illustrated in A, B, and C. Large ivory balls represent Ca. Symbols of other atoms follow the same convention used in Fig. 1. Figure is adapted from the published data in Ref (58), copyrighted by the American Physical Society and Ref (64), with permission from Elsevier.

Fig. 3.

Desorption barrier of two hydrogen atoms from (A) the metadimer configuration and (B) the paired six adatoms configuration. (C) Migration barrier of two hydrogen adatoms from the paired 24 adatoms configurations into a separated paradimer configuration. IS, TS, and FS stand for initial, transition, and final states, respectively. Blue balls are hydrogen atoms, and the network of carbon atoms is represented by the wireframe. (C, Right) The two carbon atoms from which hydrogen atoms migrated are highlighted with gray balls. Dashed lines are only a guide for the eye. (C, Inset) A zoomed-in view depicting the direction of the migration. Parts of figure adapted from the published data in Ref (75). Copyrighted by the American Physical Society.