In view of the worldwide energy challenge in the 21^st century, the technology of semiconductor-based photoelectrochemical (PEC) water splitting has received considerable attention as an alternative approach for solar energy harvesting and storage. Two-dimensional (2D) structures such as nanosheets have the potential to tap the solar energy by unlocking the functional properties at the nanoscale. Tin(II) sulfide is a fascinating solar energy material due to its anisotropic material properties. In this manuscript, we report on exploiting the 2D structure modulated optical properties of nanocrystalline SnS thin film synthesized by chemical spray pyrolysis using ambient transport in the harvesting of solar energy. We obtained the nanostructured SnS with well-preserved dimensions and morphologies with one step processing. The work demonstrates that the intrinsically ordered SnS nanostructure on FTO coated glass can tap the incident radiation in an efficient manner. The structure–property relationship to explain the photo-response in nanocrystalline-SnS is verified experimentally and theoretically. The novel design scheme for antireflection coating along with the anisotropic properties of SnS is conceived for realizing a PEC cell. The developed PEC cell consists of a SnS photoanode which shows considerably high photocurrent density of 7 mA cm⁻² with aqueous media under AM 1.5G, 100 mW cm⁻² exposure with notably stable operation. Electrochemical impedance spectroscopy revealed that a non-ideal capacitive behavior as well as drift assisted transport across the solid-state interface is responsible for such a high photo-current density in the nanocrystalline-SnS photoanode.

Spray pyrolysed thin films of quaternary Cu₂ZnSnS₄ (CZTS) were successfully deposited on soda lime glass substrates at 320 °C under a non-equilibrium condition (by varying Zn, Sn and S precursor concentrations) and without additional sulfurization. The effect of deficiency and enrichment of these three elements (normalized with respect to Cu) on the film's microstrain, optical band-gap and Hall mobility was investigated. A large non-uniform microstrain of (5–6) × 10⁻³ and compressive nature were observed for both Zn- and Sn-enriched films from Williamson–Hall analysis of x-ray diffraction (XRD) data. However, a tensile strain of (2–3) × 10⁻³ was revealed in Sn-poor and S-rich samples. The optical band-gap (E _g) in stoichiometric CZTS was found to be 1.45 eV and Hall mobility (μ _H) in the range 87–92 cm² V⁻¹ s⁻¹ was observed for S- and Zn-enriched films. The tensile nature of microstrain and inhomogeneities in E _g and μ _H were observed with greater magnitude due to the existence of other secondary phases, which were confirmed complementarily by FTIR spectroscopy and XRD.

The fulfilment of simultaneous hydrogen and oxygen evolution reactions (HER and OER) in acidic conditions is one of the challenges facing the production of green hydrogen. Herein, robust electrocatalysts using a heterostructure of Ni-sulphide (NiS, NiS₂ and Ni₃S₂) and -selenide (NiSe) supported on Ni-foam (NF) have been developed via the simple single-step thermal diffusion of S and Se. Among the various prepared hierarchical structures, Ni₃S₂@NiSe/NF shows the best catalytic activity for the HER, with low overpotentials of 103 and 289 mV at current densities of 10 and 50 mA cm⁻², respectively. It shows a promising Tafel slope of 74.2 mV dec⁻¹ in 0.5 M H₂SO₄ for the HER. The same structure also shows remarkable OER activity in acidic conditions, with an overpotential of 0.26 V (vs. RHE) at 50 mA cm⁻² and a Tafel slope of 68.9 mV dec⁻¹. The density functional theory (DFT)-based approach reveals that the Ni₃S₂@NiSe heterointerface exhibits a very low adsorption free energy for hydrogen at the cathode and strong electron localization across its interface, which facilitates the charge-transfer kinetics at the anode to improve the sluggish OER rate. In addition, its excellent HER performance results from the strong hybridization of the Ni d orbitals with the S and Se p orbitals, destabilizing their antibonding characteristics.

This work describes ex situ Cu-doped SnS demonstrating a large J _ph = 3.2 mA cm ⁻² as a photocathode and enhanced V _OC = 465 mV in a hetero-junction solar cell.