Metal functionalization of graphene for hydrogen storage applications

The outstanding properties of graphene, which have made it one of the most studied materials, can be tailored and enhanced by interaction with other atomic species. In particular, the decoration of graphene with metals is relevant for hydrogen storage applications. Indeed, it is known that graphene cannot store molecular hydrogen at room temperature while it is able to bind atomic hydrogen. Besides, the distance between two stacked graphene layers is too small to allow the hydrogen permeation. Here, metal decoration is useful in several ways: (a) it allows the direct interaction of graphene with molecular hydrogen, via the Kubas interaction, (b) it promotes the catalytic splitting of molecular hydrogen, and (c) it increases the layer spacing between graphene sheets through its intercalation, allowing molecular hydrogen permeation.

Epitaxial graphene represents an ideal model system to investigate both metal intercalation and its interaction with hydrogen. Our attention is focused on transition metals (Ti, Pt) and alkali metals (Li, Rb). Indeed, transition metals are promising to promote molecular hydrogen storage (see Fig. 1) and the spillover effect via catalytic splitting, while alkali metals are easy to intercalate, at relatively low temperature, providing a graphene layer spacing very close to that ideal for hydrogen permeation (see Fig. 2). For more details, see

Figure 1: Left: STM image of Ti islands on graphene. Right: Hydrogen desorption in Ti-functionalized graphene as a function of surface coverage.
Figure 2: Top: model of Li intercalation in graphene; bottom: STM image of epitaxial graphene after deposition of 0.016 ML Li.

PeopleLetizia Ferbel, Stefan Heun, Stefano Veronesi*, Ylea Vlamidis, Emanuele Pompei
KeywordsHydrogen storage, graphene, metal functionalization
Methods, techniquesSTM, LEED, TDS, Raman spectroscopy.
CollaborationsChia-Hao Chen (National Synchrotron Radiation Research Center, Hsinchu, Taiwan) and Chung-Lin Wu (Department of Physics, National Cheng Kung University, Tainan, Taiwan)
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