Hydrothermal preparation of NiO/La-NaTaO3 composite photocatalyst for degradation of ammonium dibutyl dithiophosphate wastewater

The discharge of a large amount of flotation reagents wastewater can cause significant environmental pollution. In this study, NiO/La-NaTaO3 nano-photocatalyst was prepared and applied to degrade synthetic flotation reagent ammonium dibutyl dithiophosphate wastewater. Various characterization results confirmed the successful synthesis of NiO/La-NaTaO3, and UV-vis DRS analysis revealed a band gap of 3.96 eV for 4 wt% NiO/2.5% La-NaTaO3. Under UV light, the degradation rate of 20 mg 4 wt% NiO/2.5% La-NaTaO3 photocatalyst reached its optimum within 4.5 h at pH=3, exhibiting a 1.45 times improvement compared to pure NaTaO3. Radical trapping experiments and EPR results showed that ·OH and·O2- showed major contribution to the degradation. Furthermore, photocatalytic mechanisms and toxicity evolution were investigated, demonstrating the potential application of photocatalytic methods for treating flotation reagent wastewater.

Photoelectrochemical Degradation of Organic Pollutants on a La3+ Doped BiFeO3 Perovskite

Towards nonconventional wastewater treatment methods for the degradation of organic pollutants in wastewater, a perovskite-based photoelectrochemical system was developed. Bismuth ferrite doped with lanthanum (La-BiFeO3, La-BFO) perovskite was synthesised through a hydrothermal method with low calcination temperature for the photoelectrochemical degradation of orange II dye and other cocktails of dyes. Photoanodes were prepared by the deposition of the perovskites on a fluorine-doped tin oxide (FTO) substrate. The photoanodes were characterised using XRD, FESEM, FTIR and UV-vis diffuse reflectance. The photoelectrochemical properties of the synthesised photoanodes were investigated with chronoamperometry and electrochemical impedance spectroscopy (including Mott–Schottky analysis). The results show that all La3+-doped BFO photoanodes exhibited a higher absorption edge in the visible light region than the undoped BFO. The photocurrent response of 10% La-BFO (the best performing electrode) exhibited a three times higher current response than the pure BFO. In addition, the electrode exhibited a good degradation efficiency of 84.2% within 120 min with applied bias potential of 2 V at a pH of 7. EIS studies showed a significant enhancement of the interfacial electron transfer of the charge carriers. The enhancements in electrode performances were attributed to the synergistic effect of the applied bias potential and the introduction of La3+ into the BFO matrix. This study therefore shows that the photoelectrocatalytic performance of BFO for water treatment can be improved by the introduction of perovskites-doping ions such as La3+.

Nickel and sulfur codoped TiO2 nanoparticles for efficient visible light photocatalytic activity

In this work, Nickel (Ni) and sulfur (S) codoped TiO2 nanoparticles were prepared by a sol-gel technique. The as-prepared catalyst was characterized using X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), FT-Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectra (DRS) for investigating crystal structure, crystal phase, particle size and bandgap energy of these samples. The photocatalytic performances of all the prepared catalysts have been investigated for the degradation of methylene blue (MB) under visible light irradiation. It was noticed that Ni-S codoped TiO2(Ni-S/TiO2) nanoparticles exhibited much higher photocatalytic activity compared with pure, Ni and S doped TiO2 due to higher visible light absorption and probable decrease in the recombination of photo-generated charges. It was decided that the great visible light absorption was created for codoped TiO2 by the formation of impurity energy states near both the edges of the collection, which works as trapping sites for both the photogenerated charges to decrease the recombination process.

Pyrochlore oxides as visible light-responsive photocatalysts

This perspective describes the use of pyrochlore oxides in photocatalysis with focus on the strategies to enhance their activity.

One-step controllable synthesis of three-dimensional WO3 hierarchical architectures with different morphologies decorated with silver nanoparticles: enhancing the photocatalytic activity

Hierarchical architecture self-assembled three-dimensional WO₃ and WO₃·Ag with high uniformity have been successfully obtained using peroxopolytungstic acid as precursor and silver in a morphological engineering approach under moderate hydrothermal conditions.

Hybridizing Ag-Doped ZnO nanoparticles with graphite as potential photocatalysts for enhanced removal of metronidazole antibiotic from water

In this study, the ZnO nanoparticles were doped with Ag and then hybridized on graphite (GP) layer (Ag-ZnO/GP) by a hydrothermal method, which was used as photocatalysts to remove metronidazole (MNZ) antibiotic from aqueous solutions. The fine structure, morphologies, and optical properties of the synthesized composites were first examined. The incorporation of Ag would readily reduce the rate of the recombination of electron-hole pairs and enhance the photocatalytic activity in a wide range of light wavelength. The graphite surface also acted as an electron sink to efficiently inhibit the photocorrosion of ZnO, thereby improving the photostability of the composites. The composition of the composite was optimized to be 0.5 wt% GP/ZnO and 1.0 wt% Ag/ZnO according to the extent of the enhancement of photocatalytic activity. In a solution containing 30 mg L^-1 of MNZ and 0.5 g L^-1 of Ag-ZnO/GP composite, it was shown that 88.5% and 97.3% of MNZ was removed after 60 min of 100-W UV and 180-min solar irradiation, respectively. Moreover, six over a total of eleven transformation products formed during UV photocatalysis were ascribed to the roles of reactive holes (h⁺), all which were detected and identified by high-resolution liquid chromatography-mass spectrometry (LC-MS). Finally, the pathways of MNZ degradation over Ag-ZnO/GP composite were proposed.

Ti3C2-MXene/Bismuth Ferrite Nanohybrids for Efficient Degradation of Organic Dyes and Colorless Pollutants

The current environmental and potable water crisis requires technological advancement to tackle the issues caused by different organic pollutants. Herein, we report the degradation of organic pollutants such as Congo Red and acetophenone from aqueous media using visible light irradiation. To harvest the solar energy for photocatalysis, we fabricated a nanohybrid system composed of bismuth ferrite nanoparticles with two-dimensional (2D) MXene sheets, namely, the BiFeO3 (BFO)/Ti3C2 (MXene) nanohybrid, for enhanced photocatalytic activity. The hybrid BFO/MXene is fabricated using a simple and low-cost double-solvent solvothermal method. The SEM and TEM images showed that the BFO nanoparticles are attached onto the surface of 2D MXene sheets. The photocatalytic degradation achieved by the hybrid is found to be 100% in 42 min for the organic dye (Congo Red) and 100% for the colorless aqueous pollutant (acetophenone) in 150 min. The BFO/MXene hybrid system exhibited a large surface area of 147 m2 g-1 measured via the Brunauer-Emmett-Teller sorption-desorption technique, which is found to be the largest among all BFO nanoparticles and derivatives. The photoluminescence spectra indicate a low electron-hole recombination rate. Fast and efficient degradation of organic molecules is caused by two factors: larger surface area and lower electron-hole recombination rate, which makes the BFO/MXene nanohybrid a highly efficient photocatalyst and a promising candidate for many future applications.

La- and Mn-Codoped Bismuth Ferrite/Ti3C2 MXene Composites for Efficient Photocatalytic Degradation of Congo Red Dye

Over the years, scarcity of fresh potable water has increased the demand for clean water. Meanwhile, with the advent of nanotechnology, the use of nanomaterials for photocatalytic degradation of pollutants in wastewaters has increased. Herein, a new type of nanohybrids of La- and Mn-codoped bismuth ferrite (BFO) nanoparticles embedded into transition-metal carbide sheets (MXene-Ti₃C₂) were prepared by a low-cost double-solvent sol-gel method and investigated for their catalytic activity in dark and photoinduced conditions. The photoluminescence results showed that pure BFO has the highest electron hole recombination rate as compared to all the codoped BFO/Ti₃C₂ nanohybrids. The higher electron-hole pair generation rate of the nanohybrids provides a suitable environment for fast degradation of organic dye molecules. The band gap of the prepared nanohybrid was tuned to 1.73 eV. Moreover, the BLFO/Ti₃C₂ and BLFMO-5/Ti₃C₂ degraded 92 and 93% of the organic pollutant, respectively, from water in dark and remaining in the light spectrum. Therefore, these synthesized nanohybrids could be a promising candidate for catalytic and photocatalytic applications in future.

Steering Charge Kinetics of Tin Niobate Photocatalysts: Key Roles of Phase Structure and Electronic Structure

Tin niobate photocatalysts with the phase structures of froodite (SnNb₂O₆) and pyrochlore (Sn₂Nb₂O₇) were obtained by a facile solvothermal method in order to explore the impact of phase structure and electronic structure on the charge kinetics and photocatalytic performance. By employing tin niobate as a model compound, the effects of phase structure over electronic structure, photocatalytic activity toward methyl orange solution and hydrogen evolution were systematically investigated. It is found that the variation of phase structure from SnNb₂O₆ to Sn₂Nb₂O₇ accompanied with modulation of particle size and band edge potentials that has great consequences on photocatalytic performance. In combination with the electrochemical impedance spectroscopy (EIS), transient photocurrent responses, transient absorption spectroscopy (TAS), and the analysis of the charge-carrier dynamics suggested that variation of electronic structure has great impacts on the charge separation and transfer rate of tin niobate photocatalysts and the subsequent photocatalytic performance. Moreover, the results of the X-ray photoelectron spectroscopy (XPS) indicated that the existent of Sn⁴⁺ species in Sn₂Nb₂O₇ could result in a decrease in photocatalytic activity. Photocatalytic test demonstrated that the SnNb₂O₆ (froodite) catalyst possesses a higher photocatalytic activity toward MO degradation and H₂ evolution compared with the sample of Sn₂Nb₂O₇ (pyrochlore). On the basis of spin resonance measurement and trapping experiment, it is expected that photogenerated holes, O₂^-•, and OH^• active species dominate the photodegradation of methyl orange.

Large enhanced photocatalytic activity of g-C3N4 by fabrication of a nanocomposite with introducing upconversion nanocrystal and Ag nanoparticles

A novel heterostructured nanocomposite UCNPs@SiO₂@Ag/g-C₃N₄ was developed for the first time to substantially boost the solar-light driven photocatalytic activity of g-C₃N₄. Its photocatalytic properties and photocatalytic mechanism were investigated. The as-synthesized photocatalyst with excellent improvement in the solar absorption and separation efficiency of photoinduced electron–hole pairs exhibited optimum solar-induced photocatalytic activity in dye degradation and hydrogen production. The experimental results showed that the rates of degradation of Rhodamine B (RhB) and hydrogen evolution were about 10 and 12 times higher than that of pristine g-C₃N₄, respectively. The excellent photocatalytic activity was attributed to the synergetic effect of upconversion nanoparticles (UCNPs) and Ag nanoparticles (NPs) on the modification of the photocatalytic properties of g-C₃N₄, resulting in a broad light response range for g-C₃N₄ as well as the fast separation and slow recombination of photoinduced electron–hole pairs. This study provides new insight into the fabrication of g-C₃N₄-based nanocomposite photocatalysts with high catalytic efficiency through the artful assembly of UCNPs, Ag NPs and g-C₃N₄ into a hetero-composite nanostructure. The prominent improvement in photocatalytic activity enables the potential application of g-C₃N₄ in the photocatalytic degradation of organic pollutants and hydrogen production utilizing solar energy.

A novel heterostructured nanocomposite UCNPs@SiO₂@Ag/g-C₃N₄ was developed for the first time to substantially boost the solar-light driven photocatalytic activity of g-C₃N₄.

A novel p-LaFeO3/n-Ag3PO4 heterojunction photocatalyst for phenol degradation under visible light irradiation

A novel heterojunction photocatalyst p-LaFeO3/n-Ag3PO4 has been prepared via a facile in situ precipitation method. It exhibits higher activity than individual Ag3PO4 and LaFeO3 in the degradation of phenol. The excellent activity is mainly attributed to its more effective separation of electron-hole pairs.

Phosphotungstic acid supported on aminosilica functionalized perovskite-type LaFeO3 nanoparticles: a novel recyclable and excellent visible-light photocatalyst

In this research, a novel nanohybrid compound, LaFeO₃@SiO₂–NH₂/PTA has been prepared, in which H₃PW₁₂O₄₀ (abbreviated as PTA) was successfully anchored onto the surface of 3-aminopropylsilica modified LaFeO₃.

Insight into the origin of photoreactivity of various well-defined Bi2WO6 crystals: exposed heterojunction-like surface and oxygen defects

Three kinds of Bi₂WO₆ with well-defined morphology were prepared. The nanosheet with exposed (020) facets was obtained. The origin of photoreactivity of Bi₂WO₆ photocatalysis was studied.

α-Fe2O3 nanospheres: facile synthesis and highly efficient photo-degradation of organic dyes and surface activation by nano-Pt for enhanced methanol sensing

Hematite α-Fe₂O₃ thin films have been deposited on FTO coated glass substrates. The films were found to perform efficiently towards electrochemical sensing of methanol and photodegradation of toxic dyes, viz. Indigo Carmine and Rhodamine B.