Catalytic decontamination of organic/inorganic pollutants in water and green H2 generation using nanoporous SnS2 micro-flower structured film

Recycling water and generation of H₂ simultaneously as a green technology can be a key attraction in establishing environmental sustainability. Towards this endeavor, nanoporous SnS₂ film electrodes deposited by a solution process on nickel foam demonstrate a promising electrocatalytic activity towards generation of H₂ gas at cathode while the anodic reaction leads to the decomposition of urea-waste at the rate of 10 mA cm^-2 in 1 M KOH with a lower cell-potential of 1.38 V vs RHE. The SnS₂ electrode also demonstrates an excellent catalytic activity towards hydrogen evolution reaction in a wide pH range (0-14). In addition, the SnS₂ film deposited on an FTO-substrate shows 97.56% photocatalytic-degradation of methylene-blue dye within 180 min under irradiation of visible light with a good recyclability of the photocatalyst, suggesting its high potentiality for the practical application. The demonstrated good electro- and photo-catalytic activities can be ascribed to the nanoporous structure of SnS₂ film in a flower like 3D-fashion, offering availability of abundant active catalytic sites. Our results demonstrate the application of SnS₂ nanoporous film as catalyst can be a significant greenery path for the removal of harmful inorganic/organic hazardous wastes from waste-water with simultaneous generation of green H₂ fuel.

Recent Advancements and Future Prospects in Ultrathin 2D Semiconductor-Based Photocatalysts for Water Splitting

Ultrathin two-dimensional (2D) semiconductor-mediated photocatalysts have shown their compelling potential and have arguably received tremendous attention in photocatalysis because of their superior thickness-dependent physical, chemical, mechanical and optical properties. Although numerous comprehensions about 2D semiconductor photocatalysts have been amassed up to now, low cost efficiency, degradation, kinetics of charge transfer along with recycling are still the big challenges to realize a wide application of 2D semiconductor-based photocatalysis. At present, most photocatalysts still need rare or expensive noble metals to improve the photocatalytic activity, which inhibits their commercial-scale application extremely. Thus, developing less costly, earth-abundant semiconductor-based photocatalysts with efficient conversion of sunlight energy remains the primary challenge. In this review, it begins with a brief description of the general mechanism of overall photocatalytic water splitting. Then a concise overview of different types of 2D semiconductor-mediated photocatalysts is given to figure out the advantages and disadvantages for mentioned semiconductor-based photocatalysis, including the structural property and stability, synthesize method, electrochemical property and optical properties for H2/O2 production half reaction along with overall water splitting. Finally, we conclude this review with a perspective, marked on some remaining challenges and new directions of 2D semiconductor-mediated photocatalysts.

Novel Two-Dimensional AgInS2/SnS2/RGO Dual Heterojunctions: High Spatial Charge and Toxicity Evaluation

A single semiconductor employed into photo(electro)catalysis is not sufficient for charge carrier separation. Designing a multiple heterojunction system is a practical method for photo(electro)catalysis. Herein, novel two-dimensional AgInS₂/SnS₂/RGO (AISR) photocatalysts with multiple junctions were prepared by a simple hydrothermal method. The synthesized AISR heterojunctions showed superior photoelectrochemical performance and photocatalytic degradation of norfloxacin, with a high degradation rate reaching 95%. More importantly, the toxicity of photocatalytic products decreased within the reaction process. High spatial separation efficiency of photogenerated electron-hole pairs was evidenced by optical and photoelectrochemical characterizations. Furthermore, a laser flash photolysis technique was carried on investigating the lifetime of the charge carrier of the fabricated dual heterostructures. In addition, sulfur and oxygen vacancies existed in AISR heterojunctions could largely constrain the recombination of electron-hole pairs. Density functional theory calculations were carried out to analyze the mechanism of photoinduced interfacial redox reactions, showing that reduced graphene oxide and AgInS₂ act as electron and hole trappers in the photocatalytic reaction, respectively. Due to the interfacial electric field formed from AISR dual heterojunctions, the effective spatial charge separation and transfer contributed to the boosting photo(electro)catalytic performance.

Construction of Ni-doped SnO2-SnS2 heterojunctions with synergistic effect for enhanced photodegradation activity

Construction of heterostructures with proper band alignment and effective transport and separation of photogenerated charges is highly expected for photocatalysis. In this work, Ni-doped SnO₂-SnS₂ heterostructures (NiSnSO) are simply prepared by thermal oxidation of Ni-doped hierarchical SnS₂ microspheres in the air. When applied for the photodegradation of organic contaminants, these NiSnSO exhibit excellent catalytic performance and stability due to the following advantages: (1) Ni doping leads to the enhancement of light harvesting of SnS₂ in the visible light regions; (2) the formed heterojunctions promote the transport and separation of photogenerated electrons from SnS₂ to SnO₂; (3) Ni-SnO₂ quantum dots facilitate the enrichment of reactants, provide more reactive centers and accelerate product diffusion in the reactive centers; (4) the SnS₂ hierarchical microspheres constituted by nanoplates provide abundant active sites, high structural void porosity and accessible inner surface to faciliate the catalytic reactions. As a result, the optimized NiSnSO can photodegrade 92.7% methyl orange within 80 min under the irradiation of simulated sunlight, greatly higher than those of pure SnS₂ (29.8%) and Ni-doped SnS₂ (52.1%). These results reveal that the combination of heteroatom doping and heterostructure fabrication is a very promising strategy to deliver nanomaterials for effectively photocatalytic applications.

Hierarchical SnS2/CuInS2 Nanosheet Heterostructure Films Decorated with C60 for Remarkable Photoelectrochemical Water Splitting

Rational architectural design and catalyst components are beneficial to improve the photoelectrochemical (PEC) performance. Herein, hierarchical SnS₂/CuInS₂ nanosheet heterostructure porous films were fabricated and decorated with C₆₀ to form photocathodes for PEC water reduction. Large-size CuInS₂ nanosheet films were first grown on transparent conducting glass to form substrate films. Then, small-size SnS₂ nanosheets were epitaxially grown on both sides of the CuInS₂ nanosheets to form uniform hierarchical porous laminar films. The addition of C₆₀ on the surface of the SnS₂/CuInS₂ porous nanosheets effectively increased visible light absorption of the composite photocathode. Photoluminescence spectroscopy and impedance spectroscopy analyses indicated that the formation of a SnS₂/CuInS₂ heterojunction and decoration of C₆₀ significantly increased the photocurrent density by promoting the electron-hole separation and decreasing the resistance to the transport of charge carriers. The hierarchical SnS₂/CuInS₂ nanosheet heterostructure porous films containing multiscale nanosheets and pore configurations can enlarge the surface area and enhance visible light utilization. These beneficial factors make the optimized C₆₀-decorated SnS₂/CuInS₂ photocathode exhibit much higher photocathodic current (4.51 mA cm^-2 at applied potential -0.45 V vs reversible hydrogen electrode ) and stability than the individual CuInS₂ (2.58 mA cm^-2) and SnS₂ (1.92 mA cm^-2) nanosheet film photocathodes. This study not only reveals the promise of C₆₀-decorated hierarchical SnS₂/CuInS₂ nanosheet heterostructure porous film photocathodes for efficient solar energy harvesting and conversion but also provides rational guidelines in designing high-efficiency photoelectrodes from earth-abundant and low-cost materials allowing widely practical applications.

Highly improved visible-light-induced photocatalytic performance over BiOI/Ag2CO3 heterojunctions

The heterojunctions between BiOI and Ag₂CO₃ obviously improved visible-light-driven photocatalytic activity compared with separate BiOI and Ag₂CO₃ particles.

Novel Ag2S quantum dot modified 3D flower-like SnS2 composites for photocatalytic and photoelectrochemical applications

Novel Ag₂S quantum dot modified 3D flower-like SnS₂ composites exhibit highly efficient photodegradation of MO and photocatalytic H₂ production.

Photoexcited Properties of Tin Sulfide Nanosheet-Decorated ZnO Nanorod Heterostructures

In this study, ZnO-Sn₂S₃ core-shell nanorod heterostructures were synthesized by sputtering Sn₂S₃ shell layers onto ZnO rods. The Sn₂S₃ shell layers consisted of sheet-like crystallites. A structural analysis revealed that the ZnO-Sn₂S₃ core-shell nanorod heterostructures were highly crystalline. In comparison with ZnO nanorods, the ZnO-Sn₂S₃ nanorods exhibited a broadened optical absorption edge that extended to the visible light region. The ZnO-Sn₂S₃ nanorods exhibited substantial visible photodegradation efficiency of methylene blue organic dyes and high photoelectrochemical performance under light illumination. The unique three-dimensional sheet-like Sn₂S₃ crystallites resulted in the high light-harvesting efficiency of the nanorod heterostructures. Moreover, the efficient spatial separation of photoexcited carriers, attributable to the band alignment between ZnO and Sn₂S₃, accounted for the superior photocatalytic and photoelectrochemical properties of the ZnO-Sn₂S₃ core-shell nanorod heterostructures.

C–S bond induced ultrafine SnS2 dot/porous g-C3N4 sheet 0D/2D heterojunction: synthesis and photocatalytic mechanism investigation

A C–S bond induced novel ultrafine SnS₂ dot/porous g-C₃N₄ sheet 0D/2D heterojunction for enhanced carrier separation and photocatalytic activities was developed.

Synthesis and characterization of Z-scheme In2S3/Ag2CrO4 composites with an enhanced visible-light photocatalytic performance

Efficient charge transfer at the interfaces of an In₂S₃/Ag₂CrO₄ composite, due to the formation of a Z-scheme system between In₂S₃ and Ag₂CrO₄, effectively facilitates photogenerated electron–hole pair separation.

Facile fabrication and enhanced visible-light photocatalytic activity of In2O3/Ag2CrO4 composites

The efficient charge transfer at the interfaces of In₂O₃/Ag₂CrO₄ composite due to the formation of Z-scheme system composed of In₂O₃, Ag and Ag₂CrO₄, which effectively improved the separation and transfer of photogenerated charge carriers.