Edge-Hydrogenated Germanene by Electrochemical Decalcification-Exfoliation of CaGe2: Germanene-Enabled Vapor Sensor

Two-dimensional germanene has been recently explored for applications in sensing, catalysis, and energy storage. The potential of this material lies on its graphene-like optoelectronic and chemical properties. However, pure free-standing germanene cannot be found in nature and the synthetic methods are hindering the potentially fascinating properties of germanene. Herein, we report for the first time a single-step synthesis of few-layer germanene by electrochemical exfoliation in non-aqueous environment. As a result of simultaneous decalcification and intercalation of the electrolyte’s active ions, we achieved a low-level hydrogenation of germanene that occurs at the edges of the material. The obtained edge-hydrogenated germanene flakes have a lateral size of several micrometers which possess a cubic structure. We have pioneered the potential application of edge-hydrogenated germanene for vapor sensing and demonstrated its specific sensitivity to methanol and ethanol. We have shown a selective behavior of the germanene-based sensor that appears to increase the electrical resistance in the vapors where methanol prevails. We anticipate that these results can provide a new approach for emerging layered materials with the potential utility in advanced gas sensing.