Synthesis of Novel 1T/2H-MoS2 from MoO3 Nanowires with Enhanced Photocatalytic Performance

Enhanced photo-Fenton degradation of contaminants in a wide pH range via synergistic interaction between 1T and 2H MoS2 and copolymer tea polyphenols/polypyrrole

In this study, we present the successful development of a unique photo-Fenton catalyst, 1T-2H MoS2@TP/PPy (MTP), achieved through the coating of a copolymer of tea polyphenol (TP) and polypyrrole (PPy) onto the surface of heterophase molybdenum disulfide (1T-2H MoS2). This innovative approach involves the integration of hydrothermal synthesis with copolymerization techniques. Our strategy utilizes nanoflower-like 1T-2H MoS2 as the foundational framework, which is then enveloped in TP and PPy copolymer. This innovative approach involves the integration of hydrothermal synthesis with copolymerization techniques. Our strategy utilizes nanoflower-like 1T-2H MoS2 as the foundational framework, which is then enveloped in TP and PPy copolymer. This distinctive architecture demonstrates exceptional catalytic performance owing to the hetero-phase entanglement of 1T-2H MoS2, which provides a diverse array of active sites. The coupled structure of TP and iron (TP-Fe2+/Fe3+) effectively overcome the limitation associated with the iron source. The incorporation of PPy not only reduces the recombination of photogenerated electron-hole pairs but also enhances the stability of 1T-2H MoS2. Remarkably, our experiments on the degradation of methylene blue (MB) and tetracycline (TC) degradation demonstrate that TP-Fe2+/Fe3+ significantly expands the pH applicability range of the MTP composite catalyst. Additionally, we examine several factors, including different catalysts, H2O2 addition, variations in light intensity, solution pH, temperature fluctuations, and the role of active species, to comprehensively understand their impact on the photo-Fenton degradation process. In conclusion, MTP composite exhibits robust catalytic stability and demonstrates a broad pH utilization range in the photo-Fenton oxidation process, highlighting its promising potential for a wide range of applications.

Metallic 1T phase molybdenum disulfide cocatalyst with abundant edge and substrate active sites for enhanced photocatalytic hydrogen production activity of zinc indium sulfide nanoflowers

The formation of composites by loading co-catalysts on semiconductor photocatalysts to improve hydrogen (H2) evolution performance is a feasible strategy. Metallic 1T phase molybdenum disulfide (MoS2) as cocatalysts were decorated on zinc indium sulfide (ZnIn2S4) nanoflowers by a grinding method to construct 1T-MoS2@ZnIn2S4 composites. The H2 production rate of 1T-MoS2@ZnIn2S4 composites with optimum 7 wt% 1T-MoS2 loading achieves 15.6 mmol g-1 h-1, 5.5 times higher than ZnIn2S4 nanoflowers. The apparent quantum efficiency (AQY) increases from 3.1 % (ZnIn2S4 nanoflowers) to 13.0 % (1T-MoS2@ZnIn2S4 composites) under the wavelength light irradiation at λ = 370 nm. The loading of metallic 1T-MoS2 with abundant edge and substrate active sites on ZnIn2S4 can enhance visible light absorption, promote the transfer of electrons, and inhibit carrier recombination, thereby improving photocatalytic performance. This work offers inspiration for the design of composite photocatalysts with efficient photocatalytic capabilities.

Heterophase junction engineering: Enhanced photo-thermal synergistic catalytic performance of CO2 reduction over 1T/2H-MoS2

Photocatalytic CO2 reduction technology has been proposed as a promising solution to the greenhouse effect and energy crisis. However, the lower quantum efficiency limits its practical applications. Here, we have significantly improved the photocatalytic CO2 reduction performance of MoS2 by coupling the heterophase junction (1T/2H-MoS2) construction and photo-thermal synergy strategies. At 200 °C and 42 mW·cm-2 of 420 nm LED irradiation, the CO production rate of 1T/2H-MoS2 reached 35.3 μmol·g-1·h-1, which was 3.5 and 2.8 times that of 1T-MoS2 and 2H-MoS2, respectively. In addition, only faint CO was detected under sole photo- or sole thermal catalysis conditions. Mechanism studies showed that COOH* was the key intermediate in the photo-thermal synergistic catalytic CO2 reduction over 1T/2H-MoS2. The heterophase junction engineering significantly facilitated the separation of photogenerated carriers, and the introduction of heat accelerated the charge migration and surface reaction rates. Our work provides innovative insights into the catalyst design and mechanism studies for photo-thermal synergistic catalytic CO2 reduction.

Harnessing ultrasound in photocatalysis: Synthesis and piezo-enhanced effect: A review

The photocatalytic technique has drawn far-ranging interests in addressing the current issues; however, its property suffers from the limited visible light response and rapid recombination of carriers. To address these issues, two specific approaches have been proposed to enhance the photocatalytic activity: (1) ultrasound-assisted synthesis has been utilized to prepare photocatalysts, resulting in refined grain size, increased specific surface area, and reduced photogenerated carrier recombination; (2) sonophotocatalysis and piezoelectric enhanced photocatalysis have been developed to accelerate the reaction, which utilizes the synergism between ultrasound and light. On one side, sonophotocatalysis generates cavitation bubbles which induce more reactive radicals for redox reactions. On the other side, ultrasound induces deformation of the piezoelectric material structure, which changes the internal piezoelectric potential and improves the photocatalytic performance. Currently, intensive efforts have been devoted to related research and great progress has been reached with applications in pollutant degradation, new energy production, and other fields. This work starts by elucidating the fundamental concept of ultrasound-assisted photocatalyst synthesis and photocatalysis. Then, the synergistic behavior between ultrasonic and light in ultrasonic-assisted photocatalysis has been thoroughly discussed, including pollutant degradation, water splitting, and bacterial sterilization. Finally, the challenge and outlook are investigated and proposed.

Preparation of a Hybrid TiO2 and 1T/2H-MoS2 Photocatalyst for the Degradation of Tetracycline Hydrochloride

Water pollution caused by antibiotics is a growing problem. Semiconductor photocatalysis is an environmentally friendly technology that can effectively degrade organic pollutants in water. Therefore, the development of efficient photocatalysts is of great significance to solve the environmental pollution problem. In this paper, mixed-phase TiO₂ and 1T/2H-MoS₂ composite (1T/2H-MoS₂/TiO₂) were synthesized by the in situ growth method. The prepared compounds were characterized and applied to the visible-light degradation of tetracycline hydrochloride. The photocatalytic effect of 1T/2H-MoS₂/TiO₂ on tetracycline hydrochloride is significantly enhanced under visible light and has good stability. It has potential applications in the treatment of organic pollutants in water.

Tailoring of 1T Phase-Domain MoS2 Active Sites with Bridging S22-/Apical S2- Phase-Selective Precursor Modulation for Enriched HER Kinetics

Molybdenum disulfide (MoS₂) is a promising alternative electrocatalyst for hydrogen evolution reaction (HER) due to its relatively near zero hydrogen adsorption free energy (ΔG_H = 0.08) and availability as a metallic (1T) phase. The superior catalytic activity of the 1T phase over 2H is owing to the availability of dense active sites, 10⁷ fold higher conductivity, and greater hydrophilicity. However, in the synthesis of 1T-MoS₂, a highly controlled proficient method is indispensable due to its metastable nature. Besides, phase enrichment is greatly sensitive to experimental parameters such as precursor, temperature, reaction time, and solvent. In the context of precursors, to date, no single precursor has been recognized as a selective precursor for the synthesis of 1T-MoS₂. In this work, MoS₂ with high content of 1T phase (79.4%) and excessive bridging S₂^2-/apical S^2- sites has been formulated from a single precursor, that is, ammonium tetrathiomolybdate ((NH₄)₂MoS₄), ATTM). In HER, it displayed an inspired activity, that is, achieving 10 mA cm^-2 current density, it requires just 248 mV overpotential with a minimal Tafel slope value (56 mV/dec). The maximum enrichment of the 1T phase, abundant accumulation of catalytically active bridging S₂^2-/apical S^2- sites, and the complete reduction of Mo⁺⁶ to Mo⁺⁴ (absence of Mo⁺⁶) are root causes for the outstanding activity of the synthesized 1T phase-domain MoS₂. To the best of our knowledge for the very first time, here, we declare that the single source, that is, ATTM is an exclusive precursor for the selective synthesis of 1T-MoS₂ with advantageous structural features. Moreover, this expedient precursor could be more pertinent for the industrial-scale preparation of 1T phase-domain MoS₂ in near future.

Development of a magnetic MoS2 system camouflaged by lipid for chemo/phototherapy of cancer

Untargeted release of traditional chemotherapeutic drugs can damage normal tissues in the body and cause serious side effects for patients. Therefore, the research of targeted drug delivery system based on nanomaterials has become a hot topic in the field of cancer therapy. Magnetic molybdenum disulfide (mMoS₂) was modified by liposomes with a cell membrane-like structure to prepare nanocarrier complex (mMoS₂-Lipid) with high biocompatibility and stability. Then, combined photo-chemotherapeutic therapy was realized both in vitro and in vivo by its ultra-high photothermal conversion efficiency and excellent drug loading profile of mMoS₂-Lipid. The characterization showed that the lamellar magnetic molybdenum disulfide modified by liposomes was not easy to aggregate in physiological solution, and had a lower non-specific protein adsorption rate, which was beneficial for biomedical application. In vitro cell experiments exhibited a successful cellular uptake profile of MCF-7 cells with no significant cytotoxicity, while a concentration dependent cytotoxicity for both chemotherapy alone and photo-chemotherapy combined therapy. Compared with the unmodified mMoS₂, mMoS₂-Lipid injected into mice through tail vein can accumulate more in the tumor site, and in vivo anti-tumor studies have shown that the synergistic treatment of the mMoS₂-Lipid has an obvious inhibitory effect on the tumor with less toxic and side effects on mice. In conclusion, mMoS₂-Lipid treatment system provides a safe, rapid and effective choice for the treatment of breast cancer in the future.

Photolytic fate of (E)- and (Z)-endoxifen in water and treated wastewater exposed to sunlight

Endoxifen is the main active metabolite of a common cytostatic drug, tamoxifen. Endoxifen has been recently detected in the final effluent of municipal wastewater treatment plants. The antiestrogenic activity of endoxifen could bring negative effects to aquatic life if released to the water environment. This study elucidated the fate and susceptibility of (E)- and (Z)-endoxifen (2 μg mL^-1, 1:1 wt ratio between the two easily interchangeable isomers) in wastewater and receiving surface water to sunlight. Phototransformation by-products (PBPs) and their toxicity were determined. Sunlight reduced at least 83% of endoxifen concentration in wastewater samples, whereas in surface water samples, 60% of endoxifen was photodegraded after 180 min of the irradiation. In ultrapure water samples spiked with endoxifen, PBPs were mainly generated via con-rotatory 6π-photocyclization, followed by oxidative aromatization. These PBPs underwent secondary reactions leading to a series of PBPs with different molecular weights. Eight PBPs were identified and the toxicity analysis via the Toxicity Estimation Software Tool revealed that seven of these PBPs are more toxic than endoxifen itself. This is likely due to the formation of poly-aromatic core in the PBPs due to exposure to sunlight. Therefore, highly toxic PBPs may be generated if endoxifen is present in water and wastewater exposed to sunlight. The presence, fates and activities of these PBPs in surface water especially at locations close to treated wastewater discharge points should be investigated.

In Situ Growth of Metallic 1T-MoS2 on TiO2 Nanotubes with Improved Photocatalytic Performance

1T-MoS₂ is in situ grown on TiO₂ nanotubes (TNTs) using a hydrothermal method, forming a 1T-MoS₂@TNTs composite, which is confirmed by its physical characterization. The prepared composites show enhanced photocatalytic performance for the degradation of tetracycline hydrochloride under visible light, and the improved photocatalytic activity is closely related to the loaded amount of 1T-MoS₂. Therein, 0.5 wt % 1T-MoS₂@TNTs can degrade 57% in 1 h, which is the highest photocatalytic efficiency observed in experiments so far. It is speculated that the introduction of 1T-MoS₂ may optimize light absorption and charge separation/transport. The active species are identified and the reaction mechanism is proposed here.

Topochemically synthesized MoS2 nanosheets: A high performance electrode for wide-temperature tolerant aqueous supercapacitors

This work describes the formation of two-dimensional molybdenum di-sulfide (MoS₂) nanosheets via topochemical sulfurization of MoO₃ microplates and its applications towards wide-temperature tolerant supercapacitors. Physico-chemical characterizations such as XRD, FE-SEM, HR-TEM, XPS and elemental mapping analysis revealed the formation of MoS₂ nanosheets with lateral size in the range of 200 nm. The electrochemical properties of the MoS₂ electrode using three-electrode configuration tests revealed the presence of pseudocapacitive mechanism of charge-storage with a high capacitance (119.38 F g^-1) from cyclic voltammetry profiles and superior cyclic stability of 95.1% over 2000 cycles. The symmetric supercapacitor (SSC) fabricated using MoS₂ electrodes delivered a high-energy density (6.56 Wh kg^-1) and high-power density (2500 W kg^-1) with long cycle life. The electrochemical performance of the MoS₂ SSC exhibited ~121% improvement at 80 °C compared to that achieved at 20 °C and the mechanism of improved properties were examined with the use of electrochemical impedance spectroscopy. These experimental results indicate usefulness of topochemically synthesized MoS₂ for construction of wide-temperature tolerant supercapacitors that can be useful in a variety of industrial sectors.

Recent advances in photodegradation of antibiotic residues in water

Antibiotics are widely present in the environment due to their extensive and long-term use in modern medicine. The presence and dispersal of these compounds in the environment lead to the dissemination of antibiotic residues, thereby seriously threatening human and ecosystem health. Thus, the effective management of antibiotic residues in water and the practical applications of the management methods are long-term matters of contention among academics. Particularly, photocatalysis has attracted extensive interest as it enables the treatment of antibiotic residues in an eco-friendly manner. Considerable progress has been achieved in the implementation of photocatalytic treatment of antibiotic residues in the past few years. Therefore, this review provides a comprehensive overview of the recent developments on this important topic. This review primarily focuses on the application of photocatalysis as a promising solution for the efficient decomposition of antibiotic residues in water. Particular emphasis was laid on improvement and modification strategies, such as augmented light harvesting, improved charge separation, and strengthened interface interaction, all of which enable the design of powerful photocatalysts to enhance the photocatalytic removal of antibiotics.

Production and Properties of Molybdenum Disulfide/Graphene Oxide Hybrid Nanostructures for Catalytic Applications

Molybdenum disulfide (MoS₂) can be an excellent candidate for being combined with carbon nanomaterials to obtain new hybrid nanostructures with outstanding properties, including higher catalytic activity. The aim of the conducted research was to develop the novel production method of hybrid nanostructures formed from MoS₂ and graphene oxide (GO). The nanostructures were synthesized in different weight ratios and in two types of reactors (i.e., impinging jet and semi-batch reactors). Physicochemical analysis of the obtained materials was carried out, using various analytical techniques: particle size distribution (PSD), thermogravimetric analysis (TGA), FT-IR spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Due to the potential application of materials based on MoS₂ as the catalyst for hydrogen evolution reaction, linear sweep voltammetry (LSV) of the commercial MoS₂, synthesized MoS₂ and the obtained hybrid nanostructures was performed using a three-electrode system. The results show that the developed synthesis of hybrid MoS₂/GO nanostructures in continuous reactors is a novel and facile method for obtaining products with desired properties. The hybrid nanostructures have shown better electrochemical properties and higher onset potentials compared to MoS₂ nanoparticles. The results indicate that the addition of carbon nanomaterials during the synthesis improves the activity and stability of the MoS₂ nanoparticles.