Simple eco-friendly synthesis of the surfactant free SnS nanocrystal toward the photoelectrochemical cell application

Di-tert-butyltin(IV) 2-pyridyl and 4,6-dimethyl-2-pyrimidyl thiolates: versatile single source precursors for the preparation of SnS nanoplatelets as anode material for lithium ion batteries

New air and moisture stable di-tert-butyltin complexes derived from 2-mercaptopyridine (HSpy), [^tBu₂Sn(Spy)₂], [^tBu₂Sn(Cl)(Spy)] and 4,6-dimethyl-2-mercaptopyrimidine (HSpymMe₂) [^tBu₂Sn(Cl)(SpymMe₂)], have been prepared and utilized as single-source molecular precursors for the preparation of orthorhombic SnS nanoplatelets by a hot injection method and thin films by aerosol assisted chemical vapour deposition (AACVD). The complexes were characterized by NMR (¹H, ¹³C, ¹¹⁹Sn) and elemental analysis and their structures were unambiguously established by the single crystal X-ray diffraction technique. Thermolysis of these complexes in oleylamine (OAm) produced SnS nanoplatelets. The morphologies, elemental compositions, phase purity and crystal structures of the resulting Oam-capped nanoplatelets were determined by electron microscopy (SEM, TEM), energy dispersive X-ray spectroscopy (EDS) and pXRD, while the band gaps of the nanoplatelets were evaluated by diffuse reflectance spectroscopy (DRS) and were blue shifted relative to the bulk material. The morphology and preferential growth of the nanoplatelets were found to be significantly altered by the nature of the molecular precursor employed. The synthesized SnS nanoplatelets were evaluated for their performance as anode material for lithium ion batteries (LIBs). A cell comprised of an SnS electrode could be cycled for 50 cycles. The rate capability of SnS was investigated at different current densities in the range 0.1 to 0.7 A g^-1 which revealed that the initial capacity could be regained.

Vapor Phase Synthesis of SnS Facilitated by Ligand-Driven "Launch Vehicle" Effect in Tin Precursors

Extraordinary low-temperature vapor-phase synthesis of SnS thin films from single molecular precursors is attractive over conventional high-temperature solid-state methods. Molecular-level processing of functional materials is accompanied by several intrinsic advantages such as precise control over stoichiometry, phase selective synthesis, and uniform substrate coverage. We report here on the synthesis of a new heteroleptic molecular precursor containing (i) a thiolate ligand forming a direct Sn-S bond, and (ii) a chelating O^N^N-donor ligand introducing a "launch vehicle"-effect into the synthesized compound, thus remarkably increasing its volatility. The newly synthesized tin compound [Sn(SBut)(tfb-dmeda)] 1 was characterized by single-crystal X-ray diffraction analysis that verified the desired Sn:S ratio in the molecule, which was demonstrated in the direct conversion of the molecular complex into SnS thin films. The multi-nuclei (1H, 13C, 19F, and 119Sn) and variable-temperature 1D and 2D NMR studies indicate retention of the overall solid-state structure of 1 in the solution and suggest the presence of a dynamic conformational equilibrium. The fragmentation behavior of 1 was analyzed by mass spectrometry and compared with those of homoleptic tin tertiary butyl thiolates [Sn(SBut)2] and [Sn(SBut)4]. The precursor 1 was then used to deposit SnS thin films on different substrates (FTO, Mo-coated soda-lime glass) by CVD and film growth rates at different temperatures (300-450 °C) and times (15-60 min), film thickness, crystalline quality, and surface morphology were investigated.

A Review of the Synthesis, Properties, and Applications of Bulk and Two-Dimensional Tin (II) Sulfide (SnS)

Tin(II) sulfide (SnS) is an attractive semiconductor for solar energy conversion in thin film devices due to its bandgap of around 1.3 eV in its orthorhombic polymorph, and a band gap energy of 1.5–1.7 eV for the cubic polymorph—both of which are commensurate with efficient light harvesting, combined with a high absorption coefficient (10−4 cm−1) across the NIR–visible region of the electromagnetic spectrum, leading to theoretical power conversion efficiencies >30%. The high natural abundance and a relative lack of toxicity of its constituent elements means that such devices could potentially be inexpensive, sustainable, and accessible to most nations. SnS exists in its orthorhombic form as a layer structure similar to black phosphorus; therefore, the bandgap energy can be tuned by thinning the material to nanoscale dimensions. These and other properties enable SnS applications in optoelectronic devices (photovoltaics, photodetectors), lithium- and sodium-ion batteries, and sensors among others with a significant potential for a variety of future applications. The synthetic routes, structural, optical and electronic properties as well as their applications (in particular photonic applications and energy storage) of bulk and 2D tin(II) sulfide are reviewed herein.

High-Efficiency Photon-Capturing Capability of Two-Dimensional SnS Nanosheets for Photoelectrochemical Cells

Cost-effective, abundant, and non-toxic SnS nanosheet semiconductors can be used as water-splitting cells. Herein, a photoanode based on high-purity and highly crystalline SnS nanosheets was fabricated. We used sodium thiosulfate (Na2S2O3·5H2O) and stannous chloride (SnCl2·2H2O) as the tin and sulfur source materials, in place of SnCl4 and H2S gas, respectively, which have been used in previous studies. This gas-free fabrication process represents a new, environment-friendly fabrication method that can reduce the manufacturing cost of SnS nanosheets. The fabricated samples were characterized via X-ray diffraction, ultraviolet-visible spectroscopy, XPS, scanning electron microscopy, and Raman analyses. The XPS result indicated no Sn0 or Sn4+ in the S3 nanosheet; the nanosheet was SnS. These results with XRD show that the SnS nanosheet has high phase purity and crystallinity. Its direct optical band gap is 1.31 eV, and its lattice parameters are similar to those of standard SnS. The SnS nanosheet-based photoanode exhibited a maximum saturation photocurrent of 6.86 mA cm−2 at 0.57 V versus Ag/AgCl, with high stability. The most effective photocurrent for the photocatalytic water-splitting cell is attained with an increase in the surface area and developed electrical conduction. This is attributed to thermal annealing, which eliminates nanoparticle imperfections. This study confirms that SnS nanosheets are excellent candidates for water-splitting applications.

A Novel Thermochemical Metal Halide Treatment for High-Performance Sb2Se3 Photocathodes

The fabrication of cost-effective photostable materials with optoelectronic properties suitable for commercial photoelectrochemical (PEC) water splitting represents a complex task. Herein, we present a simple route to produce Sb₂Se₃ that meets most of the requirements for high-performance photocathodes. Annealing of Sb₂Se₃ layers in a selenium-containing atmosphere persists as a necessary step for improving device parameters; however, it could complicate industrial processability. To develop a safe and scalable alternative to the selenium physical post-processing, we propose a novel SbCl₃/glycerol-based thermochemical treatment for controlling anisotropy, a severe problem for Sb₂Se₃. Our procedure makes it possible to selectively etch antimony-rich oxyselenide presented in Sb₂Se₃, to obtain high-quality compact thin films with a favorable morphology, stoichiometric composition, and crystallographic orientation. The treated Sb₂Se₃ photoelectrode demonstrates a record photocurrent density of about 31 mA cm^-2 at -248 mV against the calomel electrode and can thus offer a breakthrough option for industrial solar fuel fabrication.

Benchmark performance of low-cost Sb2Se3 photocathodes for unassisted solar overall water splitting

Determining cost-effective semiconductors exhibiting desirable properties for commercial photoelectrochemical water splitting remains a challenge. Herein, we report a Sb2Se3 semiconductor that satisfies most requirements for an ideal high-performance photoelectrode, including a small band gap and favourable cost, optoelectronic properties, processability, and photocorrosion stability. Strong anisotropy, a major issue for Sb2Se3, is resolved by suppressing growth kinetics via close space sublimation to obtain high-quality compact thin films with favourable crystallographic orientation. The Sb2Se3 photocathode exhibits a high photocurrent density of almost 30 mA cm-2 at 0 V against the reversible hydrogen electrode, the highest value so far. We demonstrate unassisted solar overall water splitting by combining the optimised Sb2Se3 photocathode with a BiVO4 photoanode, achieving a solar-to-hydrogen efficiency of 1.5% with stability over 10 h under simulated 1 sun conditions employing a broad range of solar fluxes. Low-cost Sb2Se3 can thus be an attractive breakthrough material for commercial solar fuel production.