Sn-based materials in photocatalysis: A review

Development and the application of Sn-based materials have become more prevalent in recent years due to concerns regarding the energy crisis, environmental pollution, and the urgent need of constructing inexpensive and highly effective photocatalysis. The recent advancement in Sn-based materials for efficient photocatalysts, such as Sn alloys, Sn oxides, Sn sulfides, Sn selenides, Sn niobates, Sn tantalites, and Sn tungstates, is summarized in this study. Several design ideas for increasing the photoactivity of Sn-based materials in various photocatalytic applications are emphasized. In addition, we considered their present applications in energy generation (H2 evolution, CO2 reduction, and N2 fixation) and environmental remediation (air purification and wastewater treatment). As a result, the current review will deepen the reader's understanding of the properties and potential uses of Sn-based materials in photocatalysis. Hence, this paper will serve as a guide in promoting the domain of Sn-based materials for future photocatalytic technologies.

In Situ Growth of NiO@SnO2 Hierarchical Nanostructures for High Performance H2S Sensing

Heterostructured metal oxides with large specific surface area are crucial for constructing gas sensors with high performance. However, using slurry-coating and screen-printing methods to fabricate gas sensors cannot result in high uniformity and reproducibility of the sensors. Here, NiO nanowalls decorated by SnO₂ nanoneedles (NiO@SnO₂) were in situ grown on ceramic microchips via a chemical bath deposition method to detect H₂S instead of print-coating and slurry-coating methods. The morphologies and compositions of the NiO@SnO₂ hierarchical nanostructures (HNSs) were well tuned by varying the growth time of the NiO@SnO₂ HNSs to optimize the sensing performance. The response of the NiO@SnO₂ HNSs (2 h) to 1 ppm of H₂S was over 23-fold higher than that of the pure NiO nanowalls and 17-fold higher than that of the pure SnO₂ nanosheets. This dramatic enhancement is attributed to the large surface area of the NiO@SnO₂ HNSs and the p-n heterojunction at the heterointerface of SnO₂ and NiO. The variation in the depletion layers (W_SnO2 and W_NiO) at the heterointerface of SnO₂ and NiO greatly depends on the properties of the target gases (e.g., electron-withdrawing property (NO₂) or electron-donating property (H₂S)).

Fluorine-Phenanthroimidazole Porous Organic Polymer: Efficient Microwave Synthesis and Photocatalytic Activity

A porous polymer containing a fluorophenylphenanthroimidazole core was easily prepared via one-pot Suzuki-Miyaura cross-coupling reactions under microwave heating. These new metal-free polymers have demonstrated heterogeneous photocatalytic activity toward aza-Henry reaction with reasonable recyclability. Their preparation require a minimal workup to build porous networks with control over the apparent surface area and pore volume from suitable molecular building blocks containing 2-(1 H-phenanthro[9,10- d]imidazol-2-yl)-3,5-difluorophenol (PhIm-2F), as rigid and multitopic node, which afforded a conjugated porous polymer (CPP-PhIm-2F). A series of fluorinated ligands have shown their capability in the preparation of soluble and supported cationic Ru(bpy)₂(F-phenanthroimidazole) complexes by reaction with Ru(bpy)₂Cl₂ and demonstrating a beneficial effect of two fluorine atoms on the photocatalytic effect.

Enhanced H2S gas-sensing performance of Zn2SnO4 hierarchical quasi-microspheres constructed from nanosheets and octahedra

Most of the reported ternary oxides based sensors have not been realized to detect ppb-level H₂S till now. In this work, Zn₂SnO₄ hierarchical quasi-microspheres were prepared through a facile surfactant-free hydrothermal method followed by calcination in air atmosphere. The quasi-microspheres are composed of nanosheets with the thickness of 100 nm and octahedra with the average size of 0.63 μm, respectively. The sensor fabricated from such Zn₂SnO₄ hierarchical quasi-microspheres shows excellent selective response to H₂S at 133 °C with the lowest detection limit of 1 ppb. The gas response exhibits good linear relationship in the concentration range of 1-1000 ppb. Such outstanding H₂S sensing property might be attributed to its porous structure, the synergistic effect of the two typical building blocks and the surface adsorbed oxygen, and the possible sensing mechanism is also discussed.

Highly efficient heterostructured stannic disulfide/stannic anhydride hybrids: Synthesis, morphology, and photocatalytic reduction of chromium (VI) under visible light

Highly efficient heterostructured stannic disulfide/stannic anhydride (SnS₂/SnO₂) hybrids with different morphologies were fabricated via a two-step hydrothermal method. The composition and morphology of the obtained products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (DRS). The SEM images showed that core-shell structured SnS₂/SnO₂ nanotubes and hierarchical SnS₂ flowers decorated with SnO₂ particles were fabricated under different synthetic conditions. The DRS results of the hybrids showed that the absorption edges were gradually redshifted with increasing SnS₂ content. In the photocatalytic reduction of chromium (VI) under visible light, the SnS₂/SnO₂ hybrid prepared with thioacetamide addition of 0.60 g exhibited the best photocatalytic activity, which was approximately 6.8 times higher than that of pure SnS₂. This increase in the reduction performance might be ascribed to the strengthened absorption of visible light, the rapid interfacial charge transfer and the promoted charge separation efficiency. Photocurrent- response measurements, electrochemical impedance spectroscopy, and photoluminescence emission tests confirmed the faster charge transfer and efficient charge separation over the heterostructured SnS₂/SnO₂ hybrids. Lastly, a photocatalytic reduction mechanism for chromium (VI) over SnS₂/SnO₂ hybrids was proposed.