Efficient Charge Transfer in Heterostructures of CdS/NaTaO3 with Improved Visible-Light-Driven Photocatalytic Activity

Boosting the photocatalytic properties of NaTaO3 by coupling with AgBr

AgBr/NaTaO3 composites, with different molar % of NaTaO3 (Br/NTO(X%)), have been synthesized by simple precipitation methods; bare NaTaO3 was synthesized by hydrothermal procedure, while AgBr was synthesized by a precipitation procedure using cetyl-tri-methyl-ammonium bromide (CTAB) and AgNO3. Samples have been characterized by X-ray diffraction (XRD), N2 adsorption, UV–vis diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the as-prepared photo-catalysts was evaluated through photocatalytic degradation of rhodamine B (RhB), methyl orange (MO) and caffeic acid (CAFA) under UV and visible illumination. Single AgBr material and Br/NTO(X%) composites displayed the ability to absorb light in the visible region, while NaTaO3 is only photoactive under UV irradiation. Based on the position of conduction and valence bands of AgBr and NaTaO3, the heterojunction between these two photo-catalysts corresponds to a type II junction. In the case of photocatalytic degradation of RhB and CAFA, Br/NTO(x%) composites have highest photocatalytic activity than that obtained by both parental materials under the same operational conditions. AgBr and Br/NTO(x%) composites achieve a fast degradation of MO, together with a considerable adsorption capacity, attributed to the presence of a remaining amount of residual CTAB on the AgBr surface. In summary, coupling AgBr with NaTaO3 improves the photocatalytic activity under both UV and visible illumination with respect to the parental components, but the performance of the composites is highly dependent on the type of substrate to be degraded and the illumination conditions.

Visible-light photooxidation of ciprofloxacin utilizing metal oxide incorporated sol-gel processed La-doped NaTaO3 nanoparticles: A comparative study

The supper dissemination of antibiotic waste in water resources has exponentially progressed the vital water and soil pollution that affect human health and the environment. Consequently, there have been several types of research anticipated for the green mineralization of such pollutants. Herein, we intended a surfactant-aided sol-gel formation of lanthanum-doped sodium tantalate (LNTO) nanocrystals. The synthesized 13 nm averaged-size perovskite LNTO nanocrystals were responsive to visible-light irradiation by incorporation of 4.4-5.2 nm oxide nanoparticles, namely Bi₂O₃, CdO, Fe₂O₃, and CuO at 4.0 wt% through coprecipitation. The formed nanomaterials unveiled mesostructured surface textures with specific surface areas of 199-229 m² g^-1. The obtained nanoceramics were employed for the mineralization of 10 ppm of ciprofloxacin antibiotic (CPF) as an emerging antibiotic waste in water under visible light irradiation. The CuO-incorporated LNTO exhibited the best photocatalytic oxidation of CPF after 120 min compared with other oxides with an excellent photoreaction rate of 0.0343 min^-1 which is 49 times higher than the pure LNTO. The 2.0 gL^-1 CuO/LNTO-dose achieved the full photooxidation of CPF at an oxidation speed of 0.0738 min ^-1 within just 1.0 h of visible light irradiation and magnificent regeneration ability. This enhanced activity of CuO/LNTO is regarded as significant light absorption and a bandgap energy reduction to 2.12 eV. Besides that, the heterojunction between CuO and LNTO amended the photogenerated carrier mobility and separation as concluded from the photoluminescence and photocurrent exploration. This comparative work suggests the proper design of low bandgap oxide decoration of solution-based perovskite oxide photocatalysts for promoting the visible-light mineralization of antibiotics in water.

Regeneration study of MB in recycling runs over nickel vanadium oxide by solvent extraction for photocatalytic performance for wastewater treatments

Recently, researchers are concentrating on the synthesis of composite materials to enhance the efficiency of the materials in various applications. In this work, nickel vanadium oxide (NiV₂O₆) nanocomposite material is prepared via two methods and the prepared samples have been characterized with basic studies to analyse the effect of preparation method and the reaction time. The XRD studies reveal a polycrystalline growth in both the methods. The broad XRD peaks obtained for samples prepared via hydrothermal method suggests the size reduction and 1D nanostructure formation. The SEM analysis shows the formation of 1D structures in hydrothermal and 3D microsphere structures in solvothermal methods. The possible formation mechanism behind this formation has been discussed in this manuscript. The FTIR peaks in the fingerprint region confirm the formation and vibration of metal-oxygen bonds. The large optical bandgap values obtained from Tauc plot again confirms the formation of nanostructures of the synthesized samples. The photocatalytic activity of nickel vanadium oxide on methylene blue dye under halogen light were performed and, the recyclability of the sample is investigated. It was found from the photocatalytic spectrum that, the samples prepared from both the methods shows a degradation efficiency of more than 80% within 150 min. It was confirmed that the prepared NiV₂O₆ photocatalyst samples does not lose their degradation ability even after five cycles of repeated usage.

Fabrication of AgNi Nano-alloy-Decorated ZnO Nanocomposites as an Efficient and Novel Hybrid Catalyst to Degrade Noxious Organic Pollutants

Contamination through industrial effluents is a major threat to the environment. Degradation of organic pollutants remains a major challenge, and semiconductor-based catalysis is reported to be a viable solution. Recently, AgNi bimetallic alloy nanoparticles attracted great attention with superior properties. We report the synthesis of AgNi nano-alloy particles immobilized over the surface of ZnO hexagonal rods through an in situ chemical co-reduction process to develop a novel AgNi@ZnO nanocomposite for catalytic applications. The crystal structure, phase purity, morphology, particle size, and other properties of the as-synthesized AgNi@ZnO nanocomposite were scrutinized using powder X-ray diffraction, scanning electron microscopy, Raman spectroscopy, energy-dispersive X-ray analysis, multipoint Brunauer-Emmett-Teller, and transmission electron microscopy. The composite exhibits excellent catalytic activity toward the reduction of nitroarenes and environment polluting organic dyes. The synthesized nanocomposite shows enhanced catalytic activity with an incredible reaction rate constant, noticeable low degradation time, and greater stability. The catalyst is easily recyclable and exhibits consecutive catalytic cycle usage.

NaNbO3/NaTaO3 Superlattices: Cation-Ordering Improved Band-Edge Alignment for Water Splitting and CO2 Photocatalysis

Perovskite oxide heterostructures have been extensively investigated for their excellent photocatalytic properties. Here, through hybrid density functional theory calculations, we systematically investigate the formation of NaNbO₃-NaTaO₃ (NBO-NTO) heterostructures. The sequential cations replacement in the superlattices reveals the Nb-Ta ratio range that allows the effective formation of heterostructures, which occurs through a spontaneous polarization mechanism induced by the electrostatic potential discontinuity in the interface. The resulting cation ordering is responsible for the sawtooth-like potential distribution that spatially separates valence and conduction charges and reduces the heterostructure bandgap. The symmetric NBO₅/NTO₅ junction has the smallest bandgap (2.50 eV) whose transitions are associated with Nb 5d_xy orbitals on the interfacial plane. Such a relaxation mechanism provides the heterostructure with anisotropic optical properties and interface absorption peaks closer to the visible light spectrum. The phenomena strongly suggest the use of these heterostructures in photocatalytic reactions, supported by their coherent band-edge alignment with both water splitting and CO₂ reforming potentials.

Visible Light-Driven Photocatalytic Rhodamine B Degradation Using CdS Nanorods

In this work, highly crystalline CdS nanorods (NRs) were successfully synthesized by a facile, one-step solvothermal method. The as-prepared CdS NRs powder was characterized by XRD, FESEM, Raman, PL, XPS, BET, and UV-visible techniques to evaluate the structural, morphological, and optical properties. The photocatalytic performance of the as-synthesized CdS NRs was investigated for the photodegradation of RhB dye under visible light irradiations. It has been found that CdS NRs show maximum RhB degradation efficiency of 88.4% in 120 min. The excellent photodegradation ability of the CdS NRs can be attributed to their rod-like structure together with their large surface area and surface state. The kinetic study indicated that the photodegradation process was best described by the pseudo-first-order kinetic model. The possible mechanism for the photodegradation of RhB dye over CdS NRs was proposed in this paper.

Efficient Photocatalytic Degradation of RhB by Constructing Sn3O4 Nanoflakes on Sulfur-Doped NaTaO3 Nanocubes

Band structure engineering and heterojunction photocatalyst construction are efficient approaches to improve the separation of photo-induced electrons and holes, along with enhancing light response ability. By sulfur doping, sodium tantalite (NaTaO3) showed an improved photocatalytic property for the degradation of Rhodamine B (RhB). Sn3O4 nanoflakes were constructed on the surface of NaTaO3 nanocubes, forming a surface heterostructure via a simple hydrothermal process, initially. This heterostructure endows the photocatalyst with an enhanced charge separation rate, resulting in an improved photocatalytic degradation of RhB. Moreover, a possible mechanism over Sn3O4/NaTaO3 and the photodegradation pathway of RhB were proposed as the combined effect of photo-induced electrons and holes. This facile process for band structure engineering and heterostructure construction provides the possibility for the practical application of high-efficiency photocatalysts.