Hydrothermal construction of flower-like MoS2 on TiO2 NTs for highly efficient environmental remediation and photocatalytic hydrogen evolution

Detecting Perfluorooctanoic Acid in Environmental Water Samples by Design of a Novel and Efficient Photoelectrochemical Sensing Platform

Contrapose the frequent occurrence of perfluorooctanoic acid (PFOA) in the environment and the serious threat to human health, it is urgent to establish effective analytical methods for monitoring PFOA levels in the environment. In this work, a novel and efficient PEC sensing platform was developed for the detection of PFOA based on CuSe/CdSe/TiO2 nanotube arrays (NTs) composites as the photoactive material and anti-PFOA aptamer as the biorecognition element. First, CdSe quantum dots (QDs) with a narrow band gap were decorated on TiO2 NTs surface. Furthermore, CuSe/CdSe/TiO2 NTs composites with a p-n heterojunction structure were designed through modifying p-type semiconductor CuSe on CdSe QDs-decorated TiO2 NTs. The as-prepared composites greatly enhanced visible light absorption and promoted charge separation, exhibiting good PEC activity. Attributed to the specific recognition of aptamer molecules immobilized on the composites toward PFOA, the formed PFOA-aptamer complexes introduced significant steric hindrance at the sensing interface, thereby impeding electron transfer and reducing the photocurrent density, and the variation in photocurrent density enabled quantitative determination of PFOA. The constructed PEC sensing platform has high sensitivity and specificity to PFOA, with a detection limit of 0.053 pg/L. Furthermore, the performance of the sensor in various environmental water samples was studied, yielding satisfactory results. Therefore, a simple and efficient PEC sensing technique has been established, providing a new solution for highly sensitive and specific detection of PFOA in the environment.

Integration of ohmic junction and step-scheme heterojunction for enhanced photocatalysis

A novel and efficient photocatalyst, Cu2WS4/MoS2-Au plasmonic Step-scheme (S-scheme) heterojunction, was constructed for the first time and applied to remove environmental pollutants. Among all the prepared photocatalysts, the. Cu2WS4/MoS2-Au-5 exhibited the highest catalytic activity with an 89.1% reduction efficiency for Cr6+ and a 98.7% oxidation efficiency for Benzophenone-1 (BP-1) under visible light irradiation. The Cu2WS4/MoS2-Au photocatalyst exhibits stable performance and efficient photocatalytic activity due to effective charge separation, enhanced light absorption from localized surface plasmon resonance (LSPR) of gold nanoparticles, and the formation of an S-scheme heterojunction with strong oxidation-reduction capabilities. In addition, through analysis of experiments and theoretical calculations, it is speculated that the Cu2WS4/MoS2-Au follows a typical S-scheme photogenerated carrier transferring mechanism, which is verified by the finite difference time domain simulation, the free radical quenching experiments, the electron paramagnetic resonance analysis and the simulated charge density distribution. More importantly, the simulations of the work function and charge density distribution confirm the built-in electric field and the ohmic junction have been established at the interfaces between the Cu2WS4 and MoS2 (Cu2WS4/MoS2) as well as the interface between MoS2 and Au (MoS2-Au), respectively. The built-in electric field and ohmic junction enable efficient separation of photogenerated electrons and holes, ensuring the superior catalytic oxidation and reduction activities of the Cu2WS4/MoS2-Au photocatalyst. Finally, we propose a photocatalytic mechanism for the Cu2WS4/MoS2-Au plasmonic S-scheme heterojunction based on experimental results and simulated calculations. The research results of this study are significance for the development of the plasmonic S-scheme photocatalytic system.

Fast photocatalytic degradation of rhodamine B using indium-porphyrin based cationic MOF under visible light irradiation

A broad light-harvesting range and efficient charge separation are two main ways to enhance the visible photocatalytic performance of semiconductors. Herein, an ionic porphyrin MOF [In(TPyP)]·(NO3) (1) (TPyP = 5,10,15,20-tetrakis(4-pyridyl)-21H,23H-porphyrin) was synthesized via in situ metalation. The orderly arranged porphyrin photosensitizer and the internal electric field between the MOF host and NO3- guests enable effective visible light response and electron-hole separation. Consequently, the as-synthesized MOF shows efficient photocatalytic degradation of rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) organic pollutants. It can degrade 99.07% of RhB within only 20 minutes under visible light irradiation (λ > 420 nm) with a high chemical reaction rate constant of 0.2400 min-1. The photocatalytic activity of the title MOF is more efficient than those of other reported MOFs, COFs and even inorganic semiconductors. The reusability, energy level, band gap, charge distribution and main degradation mechanisms of the photocatalyst were well studied.

Photocatalytic Activity of MoS2 Nanoflower-Modified CaTiO3 Composites for Degradation of RhB under Visible Light

Nanoflower-like MoS₂ deposited on the surface of rectangular CaTiO₃(CTO) was designed and synthesized via a simple template-free strategy. Through SEM, TEM, and other characterization methods, the MoS₂ nanoflowers were confirmed to be well deposited on the surface of CTO. LED was used as the visible light source, and rhodamine B (RhB) in an aqueous solution was used as the model pollutant to assess the photodegradation activity of the samples. The results showed that the MoS₂/CaTiO₃(MCTO) composite significantly improved the photocatalytic degradation of rhodamine B (RhB) in water, compared with a single CTO, and with the MCTO-2 composite photocatalysts, 97% degradation of RhB was achieved in 180 min, and its photocatalytic activity was about 5.17 times higher than that of the bare CTO. The main reasons for enhancing photocatalytic performance are the strong interaction between the nanoflower-like MoS₂ and rectangular CTO, which can lead to the effective separation of electron transfer and photoexcited electron-hole pairs in MCTO composites. This work provides a new notion for researching an effective method of recycling catalytic materials.

Recent Progress in Photocatalytic Removal of Environmental Pollution Hazards in Water Using Nanostructured Materials

Water pollution has become a critical issue because of the Industrial Revolution, growing populations, extended droughts, and climate change. Therefore, advanced technologies for wastewater remediation are urgently needed. Water contaminants are generally classified as microorganisms and inorganic/organic pollutants. Inorganic pollutants are toxic and some of them are carcinogenic materials, such as cadmium, arsenic, chromium, cadmium, lead, and mercury. Organic pollutants are contained in various materials, including organic dyes, pesticides, personal care products, detergents, and industrial organic wastes. Nanostructured materials could be potential candidates for photocatalytic reduction and for photodegradation of organic pollutants in wastewater since they have unique physical, chemical, and optical properties. Enhanced photocatalytic performance of nanostructured semiconductors can be achieved using numerous techniques; nanostructured semiconductors can be doped with different species, transition metals, noble metals or nonmetals, or a luminescence agent. Furthermore, another technique to enhance the photocatalytic performance of nanostructured semiconductors is doping with materials that have a narrow band gap. Nanostructure modification, surface engineering, and heterojunction/homojunction production all take significant time and effort. In this review, I report on the synthesis and characterization of nanostructured materials, and we discuss the photocatalytic performance of these nanostructured materials in reducing environmental pollutants.

Enhanced degradation of amiloride over Bi2FeNbO7/bisulfite process: Key factors and mechanism

Construction of Bi₂FeNbO₇/bisulfite system for abatement of pharmaceutical residue was achieved. An attempt to synthesize Bi₂FeNbO₇ through hydrothermal technique was confirmed by X-ray diffraction. The magnetic field experiment revealed that Bi₂FeNbO₇ possessed a saturation magnetization of 6.99 emu/g, indicating magnetic attributes of Bi₂FeNbO₇. Scanning electron microscopy images showed that Bi₂FeNbO₇ exhibited regular octahedra in the size of 200-300 nm. In a self-made device, the activation of sodium bisulfite using Bi₂FeNbO₇ for the disposal of amiloride has been carefully explored. The effects of solution pH, sodium bisulfite concentration, Bi₂FeNbO₇ dosage, amiloride concentration, coexisting ions, and water matrix on the performance of Bi₂FeNbO₇/bisulfite system was investigated. The catalytic performance of Bi₂FeNbO₇/bisulfite to degrade amiloride was considerably higher than that of traditional iron oxides. The maximum removal efficiency of amiloride was 97.9% in Bi₂FeNbO₇/bisulfite process. The involvement of Fe might be crucial for activating bisulfite to create active species. The dominating radical in Bi₂FeNbO₇/bisulfite process was identified as SO₃^•‒. With the help of UHPLC/MS/MS, three new degradation products of amiloride were found. Dehalogenation and deamination of amiloride might account for the formation of these transformation products. This work provides a highly efficient Bi₂FeNbO₇/bisulfite process for the disposal of pharmaceutical pollutants in water treatment.

Optical and Photocatalytic Properties of Br-Doped BiOCl Nanosheets with Rich Oxygen Vacancies and Dominating {001} Facets

Crystal facet engineering and nonmetal doping are regarded as effective strategies for improving the separation of charge carriers and photocatalytic activity of semiconductor photocatalysts. In this paper, we developed a facial method for fabricating oxygen-deficient Br-doped BiOCl nanosheets with dominating {001} facets through a traditional hydrothermal reaction and explored the impact of the Br doping and specific facets on carrier separation and photocatalytic performance. The morphologies, structures, and optical and photocatalytic properties of the obtained products were characterized systematically. The BiOCl samples prepared by the hydrothermal reaction exhibited square-like shapes with dominating {001} facets. Photodeposition results indicated that photoinduced electrons preferred to transfer to {001} facets because of the strong internal static electric fields in BiOCl nanosheets with dominating {001} facets. Br doping not only contributed to the formation of impurity energy levels that could promote light absorption but introduced a large number of surface oxygen vacancies (VO) in BiOCl photocatalysts, which was beneficial for photocatalytic performance. Moreover, the photocatalytic activities of these products under visible light were tested by degradation of rhodamine B (RhB). Because of the synergistic effect of the dominating {001} facets, Br doping, and rich VO, oxygen-deficient Br-doped BiOCl nanosheets exhibited improved carrier separation, visible light absorption, and photocatalytic efficiency.

MoS2 as a Co-Catalyst for Photocatalytic Hydrogen Production: A Mini Review

Molybdenum disulfide (MoS₂), with a two-dimensional (2D) structure, has attracted huge research interest due to its unique electrical, optical, and physicochemical properties. MoS₂ has been used as a co-catalyst for the synthesis of novel heterojunction composites with enhanced photocatalytic hydrogen production under solar light irradiation. In this review, we briefly highlight the atomic-scale structure of MoS₂ nanosheets. The top-down and bottom-up synthetic methods of MoS₂ nanosheets are described. Additionally, we discuss the formation of MoS₂ heterostructures with titanium dioxide (TiO₂), graphitic carbon nitride (g-C₃N₄), and other semiconductors and co-catalysts for enhanced photocatalytic hydrogen generation. This review addresses the challenges and future perspectives for enhancing solar hydrogen production performance in heterojunction materials using MoS₂ as a co-catalyst.

Photocatalytic degradation of dye wastewater by stepwise assembling PVA aerogel/TiO2/MoS2/Au composites in visible light

A PVA aerogel/TiO₂/MoS₂/Au catalyst formed gradually using a hydrothermal method is used to degrade Rhodamine B. SEM and TEM results show that the composite presents a uniform and well-structured porous network structure, high specific surface area and large pore diameter were proved by the results of nitrogen adsorption measurement. UV-vis DRS and PL results indicate that the composite has a high absorption rate in the visible light range, and the recombination of photogenerated electron-hole pairs can be effectively inhibited because the composite material forms a heterojunction. In the photocatalytic degradation experiment of Rhodamine B, the composite material shows high photocatalytic performance, which can reach 86% in two hours of light. The photocatalysts supported by PVA are easy to recover and have high catalytic performance even after five recycles. The study shows that PVA/TiO₂/MoS₂/Au composite material has great potential to be used for the degradation of dye wastewater.

Calcined ZnTi-Layered Double Hydroxide Intercalated with H3 PW12 O40 with Efficiently Photocatalytic and Adsorption Performances

Wastewater treatment is of great significance to environmental remediation. The exploration of efficient and stable methods for wastewater treatment is still a challenging issue. Herein, a heterojunction material with photocatalysis and adsorption properties has been designed to remove the complex pollutants from wastewater. The heterojunction material (ZnO/TiO₂ -PW₁₂ , PW₁₂ =[PW₁₂ O₄₀ ]^3- ) was synthesized by calcining the ZnTi-layered double hydroxide (ZnTi-LDH) intercalated with the Keggin-type polyoxometalate H₃ PW₁₂ O₄₀ . In the construction of ZnO/TiO₂ -PW₁₂ it was found that the polyanionic PW₁₂ remained unchanged in the process of forming the proposed heterojunction. The photochemical properties verify that heterojunction synergistic with PW₁₂ facilitated the separation of photoproduced electron-hole pairs and thus suppressed the recombination. Therefore, ZnO/TiO₂ -PW₁₂ exhibits excellent photocatalytic property, and the efficiency of Cr(VI) photoreduction reached more than 90 % in the first 3 min. Furthermore, the electrostatic force between the PW₁₂ and cationic dyes makes ZnO/TiO₂ -PW₁₂ having an outstanding adsorption performance for cationic dyes, such as rhodamine B, crystal violet and methyl blue. Such heterojunction material combined with polyoxometalate puts forward new insights for the design of functional materials for water treatment with low cost and high efficiency.

MOF-derived porous TiO2 decorated with n-type Cu2O for efficient photocatalytic H2 evolution

Type-I Cu2O/TiO2 with a porous structure has excellent photocatalytic activity for hydrogen production because of the effectively separated electron–hole pairs.