Three-dimensional porous MoS2 nanobox embedded g-C3N4@TiO2 architecture for highly efficient photocatalytic degradation of organic pollutant

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.

A novel method for the remediation of wastewater containing acid red 131 dye using acoustic cavitation combined with sulphur-doped TiO2 and oxidants

The present study investigated the degradation of Acid Red 131 (AR131) dye using a combination of ultrasound-induced cavitation, ultraviolet (UV) irradiation, chemical oxidants, and photocatalyst, focusing on the effect of operating parameters. It was established that acidic pH, higher input power, and lower initial concentration resulted in higher degradation. Sulphur-doped titanium dioxide (S-TiO2) synthesized using a novel ultrasound-assisted method showed an optimum dosage of 300 ppm for the AR131 degradation with sulphur to titanium ratio of 2:1. In the combination approach, the optimum dosage of hydrogen peroxide (H2O2) and potassium persulfate (KPS) was established as 100 ppm and 400 ppm respectively. The maximum degradation of 90.3% was obtained using a combined approach of US + KPS + UV/S-TiO2 whereas, a maximum synergetic coefficient of 1.57 was obtained for the approach of US + UV/S-TiO2 with degradation of 86.96%. It was also elucidated that for combination approaches of US + H2O2, US + H2O2 + KPS, and US + H2O2 + KPS + UV/S-TiO2, the synergetic coefficients were lower than one due to undesirable side reactions and radical scavenging. Scale-up studies performed at 15 times of the laboratory scale volume, elucidated that the maximum degradation was obtained as 58.01% for the approach of US + KPS + UV/S-TiO2. Therefore, the approach of US + KPS + UV/S-TiO2 was elucidated as the most efficient in degrading the AR131 dye at both small and large scale of operation. In terms of synergy, the approach of US + UV/S-TiO2 was more efficient. Overall, an optimized combination approach was successfully demonstrated for the effective degradation of AR131 dye with synergism and better results at a large scale.

Impact of alternate Mn doping in ternary nanocomposites on their structural, optical and antimicrobial properties: Comparative analysis of photocatalytic degradation and antibacterial activity

The present study was done to investigate and compare the photocatalytic and antibacterial activity of two in situ Manganese doped ternary nanocomposites. The dual ternary hybrid systems comprised Mn-doped Ag₂WO₄ coupled with MoS₂-GO and Mn-doped MoS₂ coupled with Ag₂WO₄-GO. Both hierarchical alternate Mn-doped ternary heterojunctions formed efficient plasmonic catalysts for wastewater treatment. The novel nanocomposites were well-characterized using XRD, FTIR, SEM-EDS, HR-TEM, XPS, UV-VIS DRS, and PL techniques confirming the successful insertion of Mn⁺² ions in respective host substrates. The bandgap of the ternary nanocomposites evaluated by the tauc plot showed them visible light-active nanocomposites. The photocatalytic ability of both Mn-doped coupled nanocomposites was investigated against the dye methylene blue. Both ternary nanocomposites showed excellent sunlight harvesting ability for dye degradation in 60 min. The maximum catalytic efficiency of both photocatalysts was obtained at a solution pH value of 8, photocatalyst dose and oxidant dose of 30 mg/100 mL and 1 mM for Mn-Ag₂WO₄/MoS₂-GO, 50 mg/100 mL, 3 mM for Mn-MoS₂/Ag₂WO₄-GO keeping IDC of 10 ppm for all photocatalysts. The nanocomposites showed excellent photocatalytic stability after five successive cycles. The response surface methodology was used as a statistical tool for the evaluation of the photocatalytic response of several interacting parameters for dye degradation by ternary composites. The antibacterial activity was determined by the inactivation of gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria by support-based doped ternary hybrids.

Spinach-derived boron-doped g-C3N4/TiO2 composites for efficient photo-degradation of methylene blue dye

Green synthesis of nanoparticles can be beneficial due to their low toxicity, cost-effectiveness, and environment-friendliness. Its synthesis involves the use of eco-friendly and biodegradable materials such as plant extracts, natural products, and microorganisms to reduce the negative environmental impacts of traditional nanoparticle synthesis methods. Herein, Spinacia oleracea leaves are used as a boron source, and a visible light active photo-catalyst is produced. The effect of Co-Catalyst Boron in Graphitic carbon nitride based nanocomposites for methylene blue dye photo-degradation in water is examined. Titanium dioxide (TiO₂) was activated by changing the hydrogen potential value while utilizing a typical orange dye as a sensitizer. The graphitic carbon nitride/TiO₂ nanocomposites were synthesized through a hydrothermal technique. To improve their performance, Boron used as a co-catalyst and B-doped g-C₃N₄/TiO₂nanocomposites prepared through wet chemical co-percipitate mathod. UV-visible spectroscopy, SEM and FTIR spectroscopy were used to analyze the photocatalyst and boron-doped composites in detail. The photocatalytic performance of pristine photocatalyst CNTx (x = 2%,4%,6%,8%) and B-doped CNTx composites were examined for Methylene Blue degradation in the presence of a light source. The spectroscopy analysis showed that B-doped g-C₃N₄/TiO₂ -8% nano-composites performed better than all other synthesized pristine catalysts and composites in this research. This research has demonstrated that B-doped g-C₃N₄/TiO₂ composites can provide an ideal solution for treating polluted water using visible light as a source to activate these photocatalysts.

A Review on the Progress of Optoelectronic Devices Based on TiO2 Thin Films and Nanomaterials

Titanium dioxide (TiO₂) is a kind of wide-bandgap semiconductor. Nano-TiO₂ devices exhibit size-dependent and novel photoelectric performance due to their quantum limiting effect, high absorption coefficient, high surface-volume ratio, adjustable band gap, etc. Due to their excellent electronic performance, abundant presence, and high cost performance, they are widely used in various application fields such as memory, sensors, and photodiodes. This article provides an overview of the most recent developments in the application of nanostructured TiO₂-based optoelectronic devices. Various complex devices are considered, such as sensors, photodetectors, light-emitting diodes (LEDs), storage applications, and field-effect transistors (FETs). This review of recent discoveries in TiO₂-based optoelectronic devices, along with summary reviews and predictions, has important implications for the development of transitional metal oxides in optoelectronic applications for researchers.

3D chrysanthemum-like g-C3N4/TiO2 as an efficient visible-light-driven Z-scheme hybrid photocatalyst for tetracycline degradation

Utilization of a solar-driven semiconductor as a photocatalyst to degrade antibiotic pollutants is a feasible and environmentally friendly technology. In this paper, 3D chrysanthemum-like g-C₃N₄/TiO₂ as a visible-light-driven hybrid photocatalyst with a Z-scheme heterostructure was firstly synthesized by the in situ hydrothermal synthesis method. Experiments proved that this 3D chrysanthemum-like g-C₃N₄/TiO₂ had better degradation performance toward tetracycline than TiO₂ and g-C₃N₄. In particular, when optimized g-C₃N₄/TiO₂-2 was applied for tetracycline removal (200 ml, 10 mg L^-1), the corresponding degradation efficiency could reach nearly 100% within 60 min. The improved photocatalytic activity was the result of better utilization of the heterostructure-induced visible light, more efficient charge transfer in the Z-scheme heterojunction as well as stronger redox capability. The Z-scheme degradation mechanism was supported by the trapping experiments of active species and ESR radical detection, and the whole photocatalytic process was controlled by the combined action of ˙O₂^-, h⁺ and ˙OH radicals. This study may be beneficial for the design of more efficient sunlight-driven hybrid photocatalysts and their applications in wastewater treatment.

Synthesis and application of titanium dioxide photocatalysis for energy, decontamination and viral disinfection: a review

Global pollution is calling for advanced methods to remove contaminants from water and wastewater, such as TiO₂-assisted photocatalysis.  The environmental applications of titanium dioxide have started after the initial TiO₂ application for water splitting by Fujishima and Honda in 1972. TiO₂ is now used for self-cleaning surfaces, air and water purification systems, microbial inactivation and selective organic conversion. The synthesis of titanium dioxide nanomaterials with high photocatalytic activity is actually a major challenge. Here we review titanium dioxide photocatalysis with focus on mechanims, synthesis, and applications. Synthetic methods include sol-gel, sonochemical, microwave, oxidation, deposition, hydro/solvothermal, and biological techniques. Applications comprise the production of energy, petroleum recovery, and the removal of microplastics, pharmaceuticals, metals, dyes, pesticides, and of viruses such as the severe acute respiratory syndrome coronavirus 2.

Investigation on the role of graphene-based composites for in photocatalytic degradation of phenol-based compounds in wastewater: a review

The ineptitude of conventional water management systems to eradicate noxious compounds leads to the development of advanced treatment systems. The disclosure of graphene-based photocatalytic degradation for the eradication of phenolic compounds has become the "apple of the eye" for many researchers. This review article describes the advanced research progress during the period of 2008-2021 in graphene-based nanocomposites and discusses their different synthesis methods. We will also talk about the applications of nanocomposite in water splitting, dye degradation, solar fuel generations, and organic transformations. Multicomponent heterojunction structure, co-catalyst cohering, and noble metal coupling have been inspected to enhance the photocatalytic performance of graphene-based composite by increasing charge separation and stability. The photocatalytic system's remarkable stability has been described in terms of facile recyclability. The adsorption ability of phenolic compounds has been addressed in the form of Langmuir and Freundlich adsorption isotherm with various factors (pH, concentration, the intensity of light, the effect of catalyst, the effect of time, etc.). The purpose of this review is to survey mechanisms and processes that enlist graphene-based composite in terms of efficacy and dose of catalyst required to attain 99% degradation. Nanoparticles may cause toxicity and a pretext for their toxicity has been mentioned. Finally, it is anticipated that this article could allocate consequential knowledge to fabricating graphene-based composites that are in crucial demand of being discussed in future research.

Natural Cotton Cellulose-Supported TiO2 Quantum Dots for the Highly Efficient Photocatalytic Degradation of Dyes

The artificial photocatalytic degradation of organic pollutants has emerged as a promising approach to purifying the water environment. The core issue of this ongoing research is to construct efficient but easily recyclable photocatalysts without quadratic harm. Here, we report an eco-friendly photocatalyst with in situ generated TiO₂ quantum dots (TQDs) on natural cotton cellulose (CC) by a simple one-step hydrothermal method. The porous fine structure and abundant hydroxyl groups control the shape growth and improve the stability of nanoparticles, making natural CC suitable for TQDs. The TQDs/CC photocatalyst was synthesized without the chemical modification of the TQDs. FE-SEM and TEM results showed that 5-6 nm TQDs are uniformly decorated on the CC surface. The long-term stability in photocatalytic activity and structure of more than ten cycles directly demonstrates the stability of CC on TQDs. With larger CC sizes, TQDs are easier to recycle. The TQDs/CC photocatalysts show impressive potential in the photocatalytic degradation of anionic methyl orange (MO) dyes and cationic rhodamine B (RhB) dyes.

Preparation of High-Porosity B-TiO2/C3N4 Composite Materials: Adsorption-Degradation Capacity and Photo-Regeneration Properties

Adsorption can quickly remove pollutants in water, while photocatalysis can effectively decompose organic matter. B-TiO₂/g-C₃N₄ ternary composite photocatalytic materials were prepared by molten method, and their adsorption-degradation capability under visible light conditions was discussed. The morphology of the B-TiO₂/g-C₃N₄ materials was inspected by SEM, TEM, BET, and EDS, and the results showed that close interfacial connections between TiO₂ and g-C₃N₄, which are favorable for charge transfer between these two semiconductors, formed heterojunctions with suitable band structure which was contributed by the molten B₂O₃. Meanwhile, the molten B₂O₃ effectively increased the specific surface area of TiO₂/C₃N₄ materials, thereby increasing the active sites and reducing the recombination of photogenerated electron-hole pairs and improving the photocatalytic degradation abilities of TiO₂ and g-C₃N₄. Elsewhere, the crystal structure analysis (XRD, XPS, FTIR) results indicated that the polar -B=O bond formed a new structure with TiO₂ and g-C₃N₄, which is not only beneficial for inhibiting the recombination of electron holes but also improving the photocatalytic activity. By removal experiment, the adsorption and degradation performances of B-TiO₂/g-C₃N₄ composite material were found to be 8.5 times and 3.4 times higher than that of g-C₃N₄. Above all, this study prepared a material for removing water pollutants with high efficiency and provides theoretical support and experimental basis for the research on the synergistic removal of pollutants by adsorption and photocatalysis.

Molybdenum Disulfide-Based Nanomaterials for Visible-Light-Induced Photocatalysis

Visible-light-responsive photocatalytic materials have a multitude of important applications, ranging from energy conversion and storage to industrial waste treatment. Molybdenum disulfide (MoS₂) and its variants exhibit high photocatalytic activity under irradiation by visible light as well as good stability and recyclability, which are desirable for all photocatalytic applications. MoS₂-based materials have been widely applied in various fields such as wastewater treatment, environmental remediation, and organic transformation reactions because of their excellent physicochemical properties. The present review focuses on the fundamental properties of MoS₂, recent developments and remaining challenges, and key strategies for tackling issues related to the utilization of MoS₂ in photocatalysis. The application of MoS₂-based materials in visible-light-induced catalytic reactions for the treatment of diverse kinds of pollutants including industrial, environmental, pharmaceutical, and agricultural waste are also critically discussed. The review concludes by highlighting the prospects of MoS₂ for use in various established and emerging areas of photocatalysis.

A Comprehensive Review of Graphitic Carbon Nitride (g-C3N4)-Metal Oxide-Based Nanocomposites: Potential for Photocatalysis and Sensing

g-C3N4 has drawn lots of attention due to its photocatalytic activity, low-cost and facile synthesis, and interesting layered structure. However, to improve some of the properties of g-C3N4, such as photochemical stability, electrical band structure, and to decrease charge recombination rate, and towards effective light-harvesting, g-C3N4-metal oxide-based heterojunctions have been introduced. In this review, we initially discussed the preparation, modification, and physical properties of the g-C3N4 and then, we discussed the combination of g-C3N4 with various metal oxides such as TiO2, ZnO, FeO, Fe2O3, Fe3O4, WO3, SnO, SnO2, etc. We summarized some of their characteristic properties of these heterojunctions, their optical features, photocatalytic performance, and electrical band edge positions. This review covers recent advances, including applications in water splitting, CO2 reduction, and photodegradation of organic pollutants, sensors, bacterial disinfection, and supercapacitors. We show that metal oxides can improve the efficiency of the bare g-C3N4 to make the composites suitable for a wide range of applications. Finally, this review provides some perspectives, limitations, and challenges in investigation of g-C3N4-metal-oxide-based heterojunctions.

Preparation of miscible CdS and homojunction C3N4 hybrids for efficient photocatalytic degradation of tetracycline

Preparation of high-performance photocatalysts for the degradation of organic pollutants by a simple method.

The tremendous boost for photocatalytic properties of g-C3N4: regulation from polymerization kinetics to crystal structure engineering

Graphite carbon nitride (g-C3N4) has become research hotspot owing to its special electronic structure and excellent chemical stability. Although g-C3N4 has made great progress in the field of photocatalysis, its...