Facile Synthesis of SnS and SnS₂ Nanosheets for FTO/SnS/SnS₂/Pt Photocathode

Abstract

Two-dimensional (2D) materials have attracted great attention recently. SnS/SnS 2 with sheet-like morphologies are widely used in photoelectric devices because of their excellent electronic transportation properties. In our study, by changing the mole ratios of SnCl 2 and C 2 H 5 NS at reaction temperatures as high as 280−300 °C, SnS rectangular nanosheets are converted successfully to SnS 2 hexagonal nanosheets with a one-pot method. SEM, XRD, Raman, and XPS analyses were utilized to examine the physical properties of the final products. Diffuse reflection spectra and PL spectra determined the bandgaps of SnS/SnS 2 to be about 1.49 and 2.19 eV, respectively. The photoelectric characteristics of SnS/SnS 2 nanosheets were also studied. FTO/SnS/SnS 2 / Pt photocathode was fabricated to enhance the photocurrent densities. Photocurrent densities as high as 26.7 μA/cm 2 were achieved.

Atmospheric pressure chemical vapor deposition growth of vertically aligned SnS2 and SnSe2 nanosheets

“…However, the energy does not correspond to the band gap of SnS around 825 nm (1.5 eV) and the large peak width is not characteristic of a single and well-dened energy transition. 61 A report on 2D akes of SnS 2 synthesized by a wet chemical synthesis technique, shows similar features on the PL spectrum (at 532 nm) with a sharp peak at about 580 nm (indirect excitonic peak as previously assigned) and a broader peak centered at about 660 nm. 11 The authors associated this transition to indirect exciton recombination of 4H phase of SnS 2 present in the sample, rejecting the other possibilities due to the high quality of their synthetized SnS 2 akes (no impurities, no sulfur vacancies, etc.).…”

“…10b) is composed of a one doublet, with S 2p 3/2 and S 2p 1/2 signal centered at 161.8 and 162.7 eV respectively, attributed to S 2À species in SnS 2 . 61 Both Sn 3d and S 2p conrms the successful formation of SnS 2 phase, without another phase. The Fig.…”

High-Performance Phase-Pure SnS Photocathodes for Photoelectrochemical Water Splitting Obtained via Molecular Ink-Derived Seed-Assisted Growth of Nanoplates

“…While interface engineering by depositing n-type SnS 2 on the SnS surfaces allowed the formation of a p−n junction, this yielded a low photon-tocurrent conversion efficiency in the PEC device because of the small energy-level difference, i.e., the band gap at the junction interface (E g,int ) between the conduction-band minimum (CBM) of SnS and the valence-band maximum (VBM) of SnS 2 . 20 The small E g,int , which is lower than the carrier activation energy (∼0.76 eV) of SnS, likely acts as a Shockley− Read−Hall recombination site for holes from SnS and electrons from SnS 2 . 24,25 Because SnS has relatively high energy levels of the CBM and VBM compared with other ptype semiconductors, n-type materials having a small conduction-band offset with respect to SnS are needed to achieve a high E g,int p−n junction.…”

“…Among them, Sn-based chalcogenides composed of nontoxic and earth-abundant elements are promising candidates. , In particular, orthorhombic herzenbergite tin monosulfide (SnS) has an anisotropic two-dimensional (2D) layered orthorhombic crystal structure (space group: Pbnm ) in which in-plane covalent bonds are present, while van der Waals bonds exist vertically along the [010] direction. − SnS has a suitable band gap (1.3 eV) for visible-light harvesting and exhibits a high hole mobility (∼90 cm 2 V –1 s –1 , ⊥ to the [010] axis), appropriate carrier concentrations (10 14 –10 17 cm –3 ), and a high optical absorption coefficient of 10 5 cm –1 in the visible region of the solar spectrum. − The theoretical photocurrent density of −38 mA cm –2 can be achieved using orthorhombic SnS-based photocathodes, assuming a band gap of 1.3 eV and 100% incident photon-to-current conversion under simulated AM 1.5G solar irradiation. Despite these promising characteristics, the photocurrent density of SnS-based photocathodes reported to date is insufficient for application to real PEC devices. − …”

Emerging Binary Chalcogenide Light Absorbers: Material Specific Promises and Challenges

“…55 Huang et al reported that the SnS x thin films changed from p-type to n-type when x = 1.15, as the increasing amount of Sn 4+ leads to n-type conductivity. 56 So it could be possible to form a homojunction with SnS x materials with a varied amount of S. Some groups actually have tried to fabricate SnS/SnS 2 devices, 57 but in general all SnS x materials coexist in a film and result in some detrimental effect in terms of performance. 58,59 Therefore, one important challenge in achieving high performance SnS-based solar energy conversion devices is to synthesize phase-pure SnS while suppressing the secondary phases, SnS 2 and Sn 2 S 3 .…”