Recent Progress on Germanene and Functionalized Germanene: Preparation, Characterizations, Applications, and Challenges

Abstract

A new family of single‐atom‐thick 2D germanium‐based materials with graphene‐like atomic arrangement, germanene and functionalized germanene, has attracted intensive attention due to their large bandgap and easily tailored electronic properties. Unlike carbon atoms in graphene, germanium atoms tend to adopt mixed sp2/sp3 hybridization in germanene, which makes it chemically active on the surface and allows its electronic states to be easily tuned by chemical functionalization. Impressive achievements in terms of the applications in energy storage and catalysis have been reported by using germanene and functionalized germanene. Herein, the fabrication of epitaxial germanene on different metallic substrates and its unique electronic properties are summarized. Then, the preparation strategies and the fundamental properties of hydrogen‐functionalized germanene (germanane or GeH) and other ligand‐terminated forms of germanene are presented. Finally, the progress of their applications in energy storage and catalysis, including both experimental results and theoretical predictions, is analyzed.

Towards Germanium Layered Materials as Superior Negative Electrodes for Li‐, Na‐, and K‐Ion Batteries

“…This last one is obtained from the layered CaGe 2 in which the [Ge − ] Zintl ion allows the topotactic deintercalation of Ca 2+ while preserving the Ge backbone . This germanium‐based layered material was first reported in 2000 and presents several differences compared to its bulk counterpart, for instance it has a direct band gap and exhibit a strong photoluminescence (change in color from the gray‐metallic in CaGe 2 to red in germanane), which is directly related with the presence of −OH and −H groups . Hence the nature of the ligands has a repercussion in the physical and chemical properties.…”

Xenes as an Emerging 2D Monoelemental Family: Fundamental Electrochemistry and Energy Applications

“…The crystal structures of CaSi 2 [52] and CaGe 2 [53] consist of anionic [Si] n − and [Ge] n − layers similar to 2D-Xenes, inserted by a divalent cation. [54,55] For instance, substituting H-termination in GeH with methyl-terminated germanene can improve the thermal stability (250 °C) and enhance the band gap, and yields band edge fluorescence with a ≈0.2% quantum yield.…”

A Perspective on Recent Advances in 2D Stanene Nanosheets

“…There has been significant theoretical and computational research on these mechanically robust puckered 2D structure because their tunable properties such as tuning their bandgaps with strain engineering, inducing magnetization with hydrogenation and inducing high‐sensitive surfaces on the electronic structure modification with molecular adsorptions . As predicted by theoretical and computational research on these mechanically robust puckered 2D structure, substantial experimental progress on silicene as well as germanene elemental puckered structured 2D materials has been accessed as a promising potential candidate for use in field‐effect transistors, topology‐based electronics, magnetic‐, optical‐, and thermal‐based device applications . Herewith, the first successful fabrication of next elemental epitaxial tin (Sn) atomic layer (“stanene”) on a Bi 2 Te 3 substrate in 2015 was followed by the room‐temperature realization of its dissipationless conductivity in 2018, and that encourages for more widespread studies of its fundamental properties, as compared with those of other competitive elemental 2D analogue.…”