Chemical vapor deposition synthesis of bulk layered metal chalcogenides (sulfides, phosphides, and selenides) in high yield and their applications in electrochemistry

Here we show a combined bottom-up and top-down approach to synthesize layered metal chalcogenides where (a) we synthesize in one step high yields of bulk layered materials by annealing a metal in the presence of a gas precursor (sulfur, phosphorous, or selenium) and (b) we exfoliate and dropcast few/mono-layers on a substrate from a sonicated mixture of our material in a specific solvent. It is interesting to note that, besides the structure being 2D layered, the properties of the nanomaterials synthesized slightly differ from the materials with the same stoichiometry synthesized using conventional chemical methods.

For instance, we synthesized Cu₉S₅ and characterized it using multiple spectroscopy, X-ray techniques, and electrical AFM. We found that is a highly doped, p-type material. This is critical to fabricate devices such as p-n junctions and heterojunctions, since most of the recently discovered and studied layered materials such as MoS₂, or MoSe₂ are n-type, while few materials, such as phosphorene, which suffers from rapid oxidation, are p-type. We tested the synthesized Cu₉S₅ as an electrode for Li-ion battery.

Using the same approach, we synthesized high yields of bulk layered silver sulfide (Ag₂S), which exhibits very high performance for hydrogen evolution reaction (HER) and copper phosphide (Cu₃P), which shows a promising application in supercapacitors. I will share also unpublished results on the synthesis of selenides such a silver selenide (β-Ag₂Se), copper selenide, and tungsten selenide, and their application in oxygen reduction reaction (ORR) and other electrochemical applications.

In this talk, we will discuss the synthesis, the extensive characterizations, the applications tested, and the promise of this technique for the fabrication of bulk materials for energy application and of heterojunctions based on monolayers for future electronic devices.

A. Itzhak, et al., Chem. Mater. 30 (2018) 2379–2388

V Shokhen et al, ACS Appl. Energy Mater. 2 (2019) 788-796