Elucidating the Photocatalytic Behavior of TiO₂-SnS₂ Composites Based on Their Energy Band Structure

Constructing 2D/2D ultrathin Ti3C2/SnS2 Schottky heterojunctions toward efficient tetracycline degradation

In this article, a novel 2D/2D ultrathin Ti₃C₂/SnS₂ Schottky heterojunctions have been prepared via a facile hydrothermal process. The properties of the heterojunction were fully characterized. The photocatalytic degradation performance of composites was examined by photo-degradation of tetracycline hydrochloride (TC-HCL) under visible light irradiation. Compared with single SnS₂, 3% Ti₃C₂/SnS₂ displayed the better performance, the removal rate of TC-HCL reached 87.7% and the kinetic rate constant (k) of the optimal 3% Ti₃C₂/SnS₂ composite was about 2.7 times of that of bare SnS₂. The improved photocatalytic activity of Ti₃C₂/SnS₂ is ascribed to the formation of 2D/2D Schottky heterojunction, which promotes the spatial charge separation and increases the surface reactive sites.

Microwave-assisted synthesis of defective Ca1-xAgxTi1-yCoyO3 with high photoelectrocatalytic activity for organic pollutant removal from water

CaTiO₃ is considered to be one of the most promising catalysts for the degradation of organic pollutants, but its application is limited by the wide band gap and low catalytic activity. Element doping is an effective strategy to solve these problems. Herein, a novel CaTiO₃ co-doped with Ag and Co (Ca_1-xAg_xTi_1-yCo_yO₃) was synthesized by combining co-precipitation and the microwave hydrothermal method for the first time. The crystal structure, microstructure and light absorption of the material were systematically investigated. The results showed that Ca_1-xAg_xTi_1-yCo_yO₃ had higher light absorption than pure CaTiO₃, and the band gap was reduced to 2.78 eV. First-principles calculations indicated that Ag-Ca and Co-Ti tended to form donor-acceptor defect pairs in the doping process. These defect states not only enhanced the adsorption properties, but also could be used as carrier traps to optimize the dielectric properties of CaTiO₃. In the photoelectrocatalytic system, with 0.01 g of catalyst, 98% of methylene blue in 100 mL solution (10 mg L^-1) was degraded in 150 min. In addition, Ca_1-xAg_xTi_1-yCo_yO₃ showed strong stability and excellent recyclability. The double ion co-doping technology will provide an effective strategy for improving the catalytic activity of traditional wide-band gap semiconductors.

Synthesis and Characterization of WO3/CeO2 Heterostructured Nanoparticles for Photodegradation of Indigo Carmine Dye

WO₃/CeO₂ heterostructured nanocomposites containing different WO₃ ratios (0.1, 0.3, 0.5, and 1.0 wt %) were synthesized by a precipitation method. The coupling of CeO₂ and WO₃ with a high specific surface area noticeably enhanced the photocatalytic activity of indigo carmine (IC) degradation under visible-light irradiation. The degradation rate constants (k) of 0.5 wt % WO₃/CeO₂ nanocomposites reached 4 and 5 times higher than those of CeO₂ and WO₃, respectively. Regarding the experimental results, the X-ray diffraction (XRD) patterns of the CeO₂ spherical nanoparticles and rod-shaped WO₃ were assigned to the cubic fluorite and orthorhombic phase structures, respectively. The increasing photocatalytic activity of nanocomposite samples could be attributed to the heterojunction of the photocatalysts with efficient charge separation and strong oxidative ability, which were confirmed by the photoluminescence spectra and diffuse reflectance spectrometry. The staggered heterojunction of the nanocomposite promoted efficient electron transfer and suppressed the recombination of photogenerated electrons and holes during the process.

Synthesis and enhanced photocatalytic activity of the flower-like CdS/Zn3(PO4)2 Z-scheme heteronanostructures

CdS/Zn3(PO4)2 Z-scheme heteronanostructures were prepared through a simple hydrothermal route and precipitation methods, and the efficiency for the photocatalytic degradation of MB solution can be improved greatly.

One-Pot Synthesis of Sulfur-Doped TiO2/Reduced Graphene Oxide Composite (S-TiO2/rGO) With Improved Photocatalytic Activity for the Removal of Diclofenac From Water

Sulfur-doped TiO2 (S-TiO2) composites with reduced graphene oxide (rGO), wt. % of rGO equal to 0.5%, 2.75%, and 5.0%, were prepared by a one-pot solvothermal procedure. The aim was to improve photocatalytic performance in comparison to TiO2 under simulated solar irradiation for the treatment of diclofenac (DCF) in aqueous medium. The obtained composites were characterized for physical-chemical properties using thermogravimetric analysis (TGA), X-ray diffractograms (XRD), Raman, scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), Brauner Emmett Teller (BET), and photoluminescence (PL) analyses, indicating successful sulfur doping and inclusion of rGO. Sulfur doping and rGO have successfully led to a decrease in photogenerated charge recombination. However, both antagonistic and synergistic effects toward DCF treatment were observed, with the latter being brought forward by higher wt.% rGO. The composite with 5.0 wt.% rGO has shown the highest DCF conversion at pH 4 compared to that obtained by pristine TiO2, despite lower DCF adsorption during the initial dark period. The expected positive effects of both sulfur doping and rGO on charge recombination were found to be limited because of the subpar interphase contact with the composite and incomplete reduction of the GO precursor. Consequent unfavorable interactions between rGO and DCF negatively influenced the activity of the studied S-TiO2/rGO photocatalyst under simulated solar irradiation.

Enhancement in Photoelectrochemical Performance of Optimized Amorphous SnS2 Thin Film Fabricated through Atomic Layer Deposition

Two-dimensional (2D) nanomaterials have distinct optical and electrical properties owing to their unique structures. In this study, smooth 2D amorphous tin disulfide (SnS₂) films were fabricated by atomic layer deposition (ALD), and applied for the first time to photoelectrochemical water splitting. The optimal stable photocurrent density of the 50-nm-thick amorphous SnS₂ film fabricated at 140 °C was 51.5 µA/cm² at an oxygen evolution reaction (0.8 V vs. saturated calomel electrode (SCE)). This value is better than those of most polycrystalline SnS₂ films reported in recent years. These results are attributed mainly to adjustable optical band gap in the range of 2.80 to 2.52 eV, precise control of the film thickness at the nanoscale, and the close contact between the prepared SnS₂ film and substrate. Subsequently, the photoelectron separation mechanisms of the amorphous, monocrystalline, and polycrystalline SnS₂ films are discussed. Considering above advantages, the ALD amorphous SnS₂ film can be designed and fabricated according to the application requirements.