BiOBr and BiOCl decorated on TiO2 QDs: Impressively increased photocatalytic performance for the degradation of pollutants under visible light

Efficient treatment of oily wastewater, antibacterial activity, and photodegradation of organic dyes using biosynthesized Ag@Fe3O4 nanocomposite

A significant waste (e.g., high oil content and pollutants such as heavy metals, dyes, and microbial contaminants) in water is generated during crude oil extraction and industrial processes, which poses environmental challenges. This study explores the potential of Ag@Fe3O4 nanocomposite (NC) biosynthesized using the aqueous leaf extract of Laurus nobilis for the treatment of oily wastewater. The NC was characterized using ultraviolet-visible (UV-Vis) spectrophotometry, Scanning Electron Microscopy (SEM), Fourier Transformed Infrared (FTIR) and X-Ray Diffraction (XRD) spectroscopies. The crystalline structure of the NC was determined to be face-centered cubic with an average size of 42 nm. Ag@Fe3O4 NC exhibited significant degradation (96.8%, 90.1%, and 93.8%) of Rose Bengal (RB), Methylene Blue (MB), and Toluidine Blue (TB), respectively, through a reduction reaction lasting 120 min at a dye concentration of 10 mg/L. The observed reaction kinetics followed a pseudo-first-order model, with rate constants (k-values) of 0.0284 min-1, 0.0189 min-1, and 0.0212 min-1 for RB, MB, and TB, respectively. The fast degradation rate can be attributed to the low band gap (1.9 eV) of Ag@Fe3O4 NC. The NC elicited an impressive effectiveness (99-100%, 98.0%, and 91.8% within 30 min) in removing, under sunlight irradiation, several heavy metals, total petroleum hydrocarbons (TPH), and total suspended solids (TSS) from the oily water samples. Furthermore, Ag@Fe3O4 NC displayed potent antibacterial properties and a good biocompatibility. These findings contribute to the development of efficient and cost-effective methods for wastewater treatment and environmental remediation.

Enhancing the activity and stability of Cu2O nanorods via coupling with a NaNbO3/SnS2 heterostructure for photoelectrochemical water-splitting

We synthesized a stable copper-based heterostructure catalyst, NaNbO3/SnS2/Cu2O for photoelectrochemical water-splitting applications with improved activity, stability, and inhibited photocorrosion in Cu2O.

Construction of a Z-scheme Ag2MoO4/BiOBr heterojunction for photocatalytically removing organic pollutants

How to facilitate photogenerated-carrier separation is an important step in developing excellent semiconductor photocatalysts for environmental pollutant removal. Herein, Ag₂MoO₄ (AMO) nanoparticles were assembled onto the surface of BiOBr (BOB) nanosheets to construct a highly efficient Z-scheme AMO/BOB heterojunction photocatalyst. Several analytical techniques were used to elucidate the characteristics and photocatalytic mechanism of the AMO/BOB heterojunction. Photodegradation experiments for removing methylene blue under simulated-sunlight irradiation reveal that a 20%AMO/BOB heterojunction exhibits excellent photodegradation activity with η(30 min) = 93.8% and k_app = 0.08638 min^-1, which were greater by 4.5 and 5.6 times in comparison with that of pure BOB and AMO, respectively. Based on the experimental and density functional theory (DFT) calculation results, it is proposed that the Z-scheme carrier transfer/separation mechanism dominates the enhanced photodegradation performance of the composite photocatalysts. Additionally, the potential application of AMO/BOB photocatalysts in degrading various organic pollutants (including organic dyes, antibiotics and other serious organic pollutants) was also investigated.

Recent progress on elemental sulfur based photocatalysts for energy and environmental applications

The growing needs of the rising population and blatant misuse of resources have contributed enormously to environmental problems. Among the various methods, photocatalysis has emerged as one of the effective remediation methods. The continuous search for effective photocatalysts that can be made from abundant, cheap, non-toxic materials is going on. Although sulfur is a known insulator, recent sulfur use as a visible light photocatalyst has ushered a new era in this direction. Sulfur is a non-toxic, cheap, and abundant photocatalyst, exhibiting significant photocatalytic properties. But, hydrophobicity, poor light-harvesting and high recombination rate of charge carriers in elemental sulfur photocatalyst are some of the major drawbacks of the elemental sulfur photocatalyst. The photocatalytic activity of sulfur as a single element was low, but various methods such as nanoscaling, heterojunction formation, doping and surface modifications have been used to enhance it. The review highlights sulfur's crystal structure, electronic and optical properties, and morphological changes, making it an excellent visible light photocatalyst. The article points to the limitations of sulfur as a single photocatalyst and various strategies to improve the shortcomings. More recently, there has been an emphasis on the synthesis of metal-free photocatalysts. This review provides its readers with a comprehensive detail of sulfur being used as a dopant in improving the photocatalytic properties of metal-free photocatalysts and their environmental remediation use. Finally, the conclusion and future perspectives for sulfur-based nanostructures are presented.

One-Step Coprecipitation Synthesis of BiOClxBr1-x Photocatalysts Decorated with CQDs at Room Temperature with Enhanced Visible-Light Response

BiOCl_xBr_1-x (0 ≤ x ≤ 1) solid solutions were synthesized at room temperature by one-step coprecipitation. Relative proportions of halogens in the anion layer were regulated, and thus, the band gap of BiOCl_xBr_1-x could be adjusted to suitable values to enhance the photocatalytic reaction. BiOCl_xBr_1-x exhibited enhanced visible-light response and higher photocatalytic activity in degrading rhodamine B (RhB) compared with individual BiOCl or BiOBr. Especially, BiOCl_0.5Br_0.5 showed the highest photocatalytic activity. Comparative tests showed that within 36 min the degradation rates of RhB upon BiOBr, BiOCl, and BiOCl_0.5Br_0.5 were 55.66, 24.03, and 94.91%, respectively. BiOCl_0.5Br_0.5 was further decorated with carbon quantum dots (CQDs) to promote the separation of photogenerated charge carriers. The photocatalytic activity was considerably enhanced by moderate doping of CQDs, and the degradation rate of RhB reached nearly 100% within 18 min upon 3CQDs-BiOCl_0.5Br_0.5 (the loading content of CQDs was 0.42 wt %). Active-species-trapping tests confirmed that h⁺ is the primary active species for photocatalytic degradation of RhB, whereas ^•O₂^- and e^- were the secondary ones. The synergistic effects of the band structure adjustment and CQD decoration on the photocatalytic activity were mainly expounded as the enhanced separation of photogenerated charge carriers and optimal redox potentials. In addition, the reuse and service life of the catalysts were analyzed. After five cycles, the photocatalytic activity still remained over 95%.

In-situ Pt nanoparticles decorated BiOBr heterostructure for enhanced visible light-based photocatalytic activity: Synergistic effect

Advanced functional materials for photocatalytic hydrogen (H₂) generation using abundant solar energy are the core of new and renewable energy research. In this paper, we report the in-situ deposition of platinum quantum-sized particles (Pt QDs) on bismuth oxybromide (BBr) 3D marigold flowers with exposed (101)/(110) facets (i.e. BBr-Pt) hierarchies prepared by a simple solvo-thermal method acting as a surfactant/structure stabilizer in the presence of CTAB. Synthesized samples were characterized by a series of analytical techniques. Intimate contact as demonstrated by HRTEM, effect of Pt loading in 3D-BiOBr nanostructure on photocatalytic H₂ production and crystal violet (CV) dye degradation rate under white LED light irradiation was studied. This was greatly improved by loading Pt QDs on BBr, the latter showing the highest photocatalytic activity for BBr-2Pt nanostructure, due to the synergistic effect of quantum-sized Pt nanoparticles and exposed ((101) and (110) planes). The BBr-2Pt nanostructure photocatalysts showed highest H₂ generation of 320.69 μmol g^-1, which is 142 folds larger than bare BBr (2.26 μmol g^-1).

In Situ Construction of Dye-Sensitized BiOCl/Rutile-TiO2 Nanorod Heterojunctions with Highly Enhanced Photocatalytic Activity for Treating Persistent Organic Pollutants

The construction of efficient and stable heterojunction photocatalysts with a controllable close contact interface and visible-light response is a challenging research topic in the field of photocatalysis. Herein, a series of BiOCl/rutile-TiO₂ (R-TiO₂) nanorod heterojunctions were constructed using R-TiO₂ nanorods as supporting frameworks followed by selective adsorption of Cl^- on R-TiO₂(110) facets and in situ growth of BiOCl on the surface of TiO₂ nanorods. The strong affinity of rhodamine B (RhB) as a photosensitizer for BiOCl allowed the prepared BiOCl/R-TiO₂ heterojunctions to work efficiently under visible-light irradiation. The dye-sensitized BiOCl/R-TiO₂ nanorod heterojunctions displayed promising photocatalytic performance for simultaneously treating RhB and the persistent organic pollutant 2-sec-butyl-4,6-dinitrophenol (DNBP). The highly enhanced photodegradation activity of the BiOCl/R-TiO₂ system was mainly attributed to the efficient RhB-photosensitization effect, the enhanced heterojunction effect, and the suitable conduction band match between BiOCl and R-TiO₂, which facilitated electron transfer from the excited RhB to the catalyst surface and charge separation across the BiOCl/R-TiO₂ interface, thus promoting the formation of ^•O₂^- and h⁺ as dominant active species in the reaction system for degradation of pollutants. The results demonstrate that the construction of a dye-sensitized BiOCl/R-TiO₂ heterojunction system is an effective strategy for improving the photocatalytic potential.

TiO2 nanotube arrays decorated with BiOBr nanosheets by the SILAR method for photoelectrochemical sensing of H2O2

The design and construction of a photoelectrochemical (PEC) sensor with excellent photoelectric properties and good photoelectrocatalysis activity is significant for the effective detection of analytes. In this paper, based on a two-step anodic oxidation method and successive ionic layer adsorption (SILAR) method, a TiO2 nanotube array (TNT) photoelectrochemical sensor modified with BiOBr nanosheets was constructed and applied for the detection of H2O2 for the first time. The photocurrent of the photoelectrochemical sensor increases with the increase of the H2O2 concentration under the irradiation of an 8 W UV lamp. Excellent linearity was obtained in the concentration range from 10 nM to 100 μM with a low detection limit of 5 nM (S/N = 3). This excellent photoelectrochemical performance is due to the formation of a p-n heterojunction between BiOBr and TiO2 nanotube arrays, which provides efficient separation of charge carriers and accelerates electron transport. Moreover, it is applied to detect H2O2 in milk samples and it showed a good recovery result ranging from 95.73% to 105.65%, which provides a promising new strategy for the detection of H2O2.

Comparison of Fe2TiO5/C photocatalysts synthesized via a nonhydrolytic sol-gel method and solid-state reaction method

Fe₂TiO₅/C photocatalysts were synthesized by a solid-state reaction method (Fe₂TiO₅/C_(S)) and nonhydrolytic sol–gel (NHSG) method (Fe₂TiO₅/C_(N)), where C was introduced by external carbon and in situ carbon sources, respectively. The Fe₂TiO₅/C_(N) photocatalyst with in situ carbon has much better photocatalytic degradation efficiency than that of Fe₂TiO₅/C_(S) synthesized by doping external carbon. The superiorities of in situ carbon were demonstrated by SEM, EDS, BET and photoelectrochemical analysis. Compared with Fe₂TiO₅/C_(S) using external carbon as a carbon source, Fe₂TiO₅/C_(N) with in situ carbon exhibits more uniform elemental distribution, much larger surface area, higher photocurrent density and lower resistivity of interfacial charge transfer. The results show that the introduction of in situ carbon via the NHSG method more easily promotes the separation of photogenerated electron–hole pairs, owing to the uniformity of the carbon element, thereby improving the photocatalytic activity of the photocatalyst.

Two different methods were used to prepare Fe₂TiO₅/C photocatalysts, demonstrating the superiorities of in situ carbon introduced by a NHSG method.