Preparation of Gallium Sulfide Nanosheets by Liquid Exfoliation and Their Application As Hydrogen Evolution Catalysts

Abstract

Here we demonstrate the production of large quantities of gallium sulfide (GaS) nanosheets by liquid exfoliation of layered GaS powder. The exfoliation was achieved by sonication of the powder in suitable solvents. The variation of dispersed concentration with solvent was consistent with classical solution thermodynamics and showed successful solvents to be those with Hildebrand solubility parameters close to 21.5 MPa 1/2 . In this way, nanosheets could be produced at concentrations of up to ~0.2 mg/ml with lateral sizes and thicknesses of 50-1000 nm and 3-80 layers, respectively. The nanosheets appeared to be relatively defect free although oxygen was observed in the vicinity of the edges. Using controlled centrifugation techniques, it was possible to prepare dispersions containing size-selected nanosheets.Spectroscopic measurements showed the optical properties of the dispersions to vary strongly with nanosheet size, allowing the elucidation of spectroscopic metrics for in-situ estimation of nanosheet size and thickness. These techniques allow the production of nanosheets with controlled sizes which will be important for certain applications. To demonstrate this, we prepared films of GaS nanosheets of three different sizes for use as hydrogen evolution electrocatalysts. We found a clear correlation between performance and size showing small nanosheets to be more effective. This is consistent with the catalytically active sites residing on the nanosheet edges.

Photoluminescence from Liquid‐Exfoliated WS2Monomers in Poly(Vinyl Alcohol) Polymer Composites

“…27,40,42 Details are given in the methods section. This procedure has been shown to yield dispersions with varying mean size and thickness distributions and, as we will describe below, different monolayer volume fractions.…”

“…27,42 An initial centrifugation at 0.5 krpm (24.4g, 1.5 h) was performed to remove unexfoliated material. The supernatant was subjected to further centrifugation at 2 krpm (390g, 1.5 h).…”

“…A significant advantage of this approach is its versatility; it has been used to exfoliate graphene, 24,[27][28][29][30][31] BN, 15 a range of TMDs 25,26,32,33 and TMOs 34,35 as well as black phosphorus [36][37][38][39][40] and a host of other 2D materials. 41,42 Another advantage is the inherent processability of nanosheet dispersions. They can be fractionated to select nanosheets by size, 43 mixed with dispersions of other nanomaterials to create hybrids 25,44 or fabricated into films or other structures.…”

Structural and electronic properties of monolayer group III monochalcogenides

“…To date, various MX systems such as InSe [22,23], GaS [24][25][26], GaSe [27,28], GaTe [29], and In 2 Se 3 [30,31] have been experimentally realized. Besides the fabrication, great endeavor has been dedicated to reveal the intriguing electronic and optical properties of MX and their potential applications for use in many fields [32].…”

Liquid Exfoliated Co(OH)2 Nanosheets as Low‐Cost, Yet High‐Performance, Catalysts for the Oxygen Evolution Reaction

“…[43] X-ray photo-electron spectroscopy (XPS) was used to confirm the chemical composition of the exfoliated nanosheets. [44] figure 1I (1 M NaOH). This curve shows the expected exponential increase and reaches a current density of 10 mA cm -2 at an overpotential of 440 mV.…”