A novel vacancy-strengthened Z-scheme g-C3N4/Bp/MoS2 composite for super-efficient visible-light photocatalytic degradation of ciprofloxacin

Vacancy Engineering in 2D Transition Metal Chalcogenide Photocatalyst: Structure Modulation, Function and Synergy Application

Transition metal chalcogenides (TMCs) are widely used in photocatalytic fields such as hydrogen evolution, nitrogen fixation, and pollutant degradation due to their suitable bandgaps, tunable electronic and optical properties, and strong reducing ability. The unique 2D malleability structure provides a pre-designed platform for customizable structures. The introduction of vacancy engineering makes up for the shortcomings of photocorrosion and limited light response and provides the greatest support for TMCs in terms of kinetics and thermodynamics in photocatalysis. This work reviews the effect of vacancy engineering on photocatalytic performance based on 2D semiconductor TMCs. The characteristics of vacancy introduction strategies are summarized, and the development of photocatalysis of vacancy engineering TMCs materials in energy conversion, degradation, and biological applications is reviewed. The contribution of vacancies in the optical range and charge transfer kinetics is also discussed from the perspective of structure manipulation. Vacancy engineering not only controls and optimizes the structure of the TMCs, but also improves the optical properties, charge transfer, and surface properties. The synergies between TMCs vacancy engineering and atomic doping, other vacancies, and heterojunction composite techniques are discussed in detail, followed by a summary of current trends and potential for expansion.

MoS2-based nanocomposites and aerogels for antibiotic pollutants removal from wastewater by photocatalytic degradation process: A review

Photocatalytic technologies based on molybdenum disulfide (MoS2) catalysts are effective, eco-friendly, and promising for antibiotic pollutants treatment. The technologies used by MoS2-based nanocomposites and aerogels for efficient degradation of antibiotics are reviewed in detail for the first time in this paper. The fundamental aspects of MoS2 were comprehensively scrutinized, encompassing crystal structure, optical properties, and photocatalytic principle. Then, the main synthesized methods and advantages/disadvantages for the preparation of MoS2-based nanocomposites and aerogels were systematically presented. Besides, a comprehensive overview of diverse MoS2-based nanocomposites and aerogels photo-degradation systems that enhanced the degradation of antibiotic pollutants were revealed. Meanwhile, the photo-degradation mechanism concentrated on the photoelectron transfer pathways and reactive oxygen species (ROS) were systematically evaluated. Finally, the challenges and perspectives for deeply development of MoS2-based nanocomposites and aerogels were discussed. This review may help researchers to deeply understand the research status of MoS2-based nanocomposites and aerogels for antibiotics removal, and makes clear the photo-degradation mechanism from photoelectron transfer pathways and ROS aspects of MoS2-based nanocomposites and aerogels.

Coupling Z-Scheme g-C3N4/rGO/MoS2 Ternary Heterojunction as an Efficient Visible Light Photocatalyst for Hydrogen Evolution and RhB Degradation

Coupling heterostructures to synergistically improve the light adsorption and promote the charge carrier separation has been regarded as an operative approach to advance the photocatalytic performances. However, it is still challenging to construct heterostructures with appropriate optical properties and interfacial energy structures at the same time. In this work, a Z-scheme g-C3N4/rGO/MoS2 ternary composite photocatalyst is successfully synthesized via an effective hydrothermal method. The as-synthesized g-C3N4/rGO/MoS2 composite photocatalyst exhibited significant improvement for visible light absorption and boosted the separation efficiency of photoinduced electron-hole pairs. The g-C3N4/rGO/MoS2 system exhibited optimum visible-light-induced photocatalytic activity in hydrogen (H2) from water splitting and degrading pollutant rhodamin B (RhB), which is 22 times and 5 times higher than that of pure g-C3N4, respectively. The excellent photocatalytic activities are attributed to the synergetic effects of coupling rGO, g-C3N4, and MoS2 ternary structures to the composite photocatalyst. These combinations of intimate two-dimensional nanoconjugations can effectively inhibit charge recombination and accelerate charge transfer kinetics, forming a Z-scheme-assisted photocatalytic mechanism, thereby exhibiting superior photocatalytic activity.

Recent Advances in Black Phosphorous-Based Photocatalysts for Degradation of Emerging Contaminants

The recalcitrant nature of emerging contaminants (ECs) in aquatic environments necessitates the development of effective strategies for their remediation, given the considerable impacts they pose on both human health and the delicate balance of the ecosystem. Semiconductor-based photocatalytic technology is recognized for its dual benefits in effectively addressing both ECs and energy-related challenges simultaneously. Among the plethora of photocatalysts, black phosphorus (BP) stands as a promising nonmetallic candidate, offering a host of advantages including its tunable direct band gap, broad-spectrum light absorption capabilities, and exceptional charge mobility. Nevertheless, pristine BP frequently underperforms, primarily due to issues related to its limited ambient stability and the rapid recombination of photogenerated electron-hole pairs. To overcome these challenges, substantial research efforts have been devoted to the creation of BP-based photocatalysts in recent years. However, there is a noticeable absence of reviews regarding the advancement of BP-based materials for the degradation of ECs in aqueous solutions. Therefore, to fill this gap, a comprehensive review is undertaken. In this review, we first present an in-depth examination of the fabrication processes for bulk BP and BP nanosheets (BPNS). The review conducts a thorough analysis and comparison of the merits and limitations inherent in each method, thereby delineating the most auspicious avenues for future research. Then, in line with the pathways followed by photogenerated electron-hole pairs at the interface, BP-based photocatalysts are systematically categorized into heterojunctions (Type I, Type II, Z-scheme, and S-scheme) and hybrids, and their photocatalytic performances against various ECs and the corresponding degradation mechanisms are comprehensively summarized. Finally, this review presents personal insights into the prospective avenues for advancing the field of BP-based photocatalysts for ECs remediation.

Novel Bi2WO6/MWCNT nanohybrids synthesis for high-performance photocatalytic activity of ciprofloxacin degradation under simulated sunlight irradiation

In this research, novel Bi2WO6/MWCNT nanohybrids were synthesized via a cost-effective hydrothermal route. The photocatalytic performance of these specimens was tested through the photodegradation of Ciprofloxacin (CIP) under simulated sunlight. Various physicochemical techniques systematically characterized the prepared pure, Bi2WO6/MWCNT nanohybrid photocatalysts. The XRD and Raman spectra revealed the structural/phase properties of Bi2WO6/MWCNT nanohybrids. FESEM and TEM pictures revealed the attachment and distribution of plate-like Bi2WO6 nanoparticles along the nanotubes. The optical absorption and bandgap energy of Bi2WO6 was affected by the addition of MWCNT, which was analyzed by UV-DRS spectroscopy. The introduction of MWCNT reduces the bandgap value of Bi2WO6 from 2.76 to 2.46 eV. The BWM-10 nanohybrid showed superior photocatalytic activity for CIP photodegradation; 91.3% of CIP was degraded under sunlight irradiation. The PL and transient photocurrent test confirm that photoinduced charge separation efficiency is better in BWM-10 nanohybrids. The scavenger test indicates that h+ & •O2 have mainly contributed to the CIP degradation process. Furthermore, the BWM-10 catalyst demonstrated outstanding reusability and firmness in four successive cycles. It is anticipated that the Bi2WO6/MWCNT nanohybrids will be employed as photocatalysts for environmental remediation and energy conversion. This research presents a novel technique for developing an effective photocatalyst for pollutant degradation.

Degradation of ciprofloxacin by persulfate activated by Fe(III)-doped BiOCl composite photocatalyst

Fe-BOC-X photocatalyst was successfully prepared by solvothermal method. The photocatalytic activity of Fe-BOC-X was determined by ciprofloxacin (CIP), a typical fluoroquinolone antibiotic. Under sunlight irradiation, all Fe-BOC-X showed better CIP removal performance than original BiOCl. In comparison, the photocatalyst with iron content of 50 wt% (Fe-BOC-3) has excellent structural stability and the best adsorption photodegradation efficiency. The removal rate of CIP (10 mg/L) by Fe-BOC-3 (0.6 g/L) reached 81.4% within 90 min. At the same time, the effects of photocatalyst dosage, pH, persulfate, persulfate concentration, and combinations of different systems (PS, Fe-BOC-3, Vis/PS, Vis/Fe-BOC-3, Fe-BOC-3/PS, and Vis/Fe-BOC-3/PS) on the reaction were systematically discussed. In reactive species trapping experiments, electron spin resonance (ESR) signals revealed that the photogenerated holes (h+), hydroxyl radical (•OH), sulfate radical (•SO4-), and superoxide radical (•O2-) played an important role in CIP degradation; hydroxyl radicals (•OH) and sulfate radicals (•SO4-) play a major role. Various characterization methods have demonstrated that Fe-BOC-X has larger specific surface area and pore volume than original BiOCl. UV-vis DRS indicate that Fe-BOC-X has wider visible light absorption and faster photocarrier transfer and provides abundant surface oxygen absorption sites for effective molecular oxygen activation. Accordingly, a large number of active species were produced and participated in the photocatalytic process, thus effectively promoting the degradation of ciprofloxacin. Based on HPLC-MS analysis, two possible decomposition pathways of CIP were finally proposed. The main degradation pathways of CIP are mainly due to the high electron density of piperazine ring in CIP molecule, which is mainly attacked by various free radicals. The main reactions include piperazine ring opening, decarbonylation, decarboxylation, and fluorine substitution. This study can better open up a new way for the design of visible light driven photocatalyst and provide more ideas for the removal of CIP in water environment.

Structural regulatory mechanism of phosphotungstate acid decorated graphene oxide quantum dots-chitosan aerogel and its application in ciprofloxacin degradation

Chitosan modified AGQD (amine modified graphene oxide quantum dots) and then combined with H₃PW₁₂O₄₀ to obtain CS_x@AGQD-HPW₁₂ via facile process and applied for CIP removal through pre-adsorption and photocatalytic processes. The application of chitosan could regulate the morphology and photoelectric properties effectively. CS_0.5@AGQD-HPW₁₂ was found to have the optimal CIP removal performance among all the products, the corresponding adsorption removal efficiency and pre-adsorption photocatalysis process were 72.1 % and 98.8 %, respectively. Results of toxicity assessment confirmed photocatalytic degradation process could mitigate the ecotoxicity of CIP effectively. The optimal TOC (total organic carbon) removal efficiency was about 52.1 %. Possible pathways for CIP degradation and reaction mechanism were proposed based on the results of intermediates analysis and trapping experiments. This demonstrated a novel approach to chitosan application and an eco-friendly way to remove CIP by adsorption-photocatalysis process.

Boosted photocatalytic performance of OVs-rich BiVO4 hollow microsphere self-assembled with the assistance of SDBS

In this study, monoclinic phase bismuth vanadate (BiOV₄) photocatalyst with unique hollow microsphere morphology was successfully prepared by a hydrothermal method in the existence of sodium dodecyl benzene sulfonate (SDBS). The prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron (SEM) and X-ray photoelectron spectrometer (XPS) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). Experimental results show that SDBS definitely changes the microstructure of BiVO₄, which is allocated to the template role of SDBS in the preparation process. Moreover, the hydrothermal treatment time is also of crucial importance in affecting the structure and morphology of the photocatalysts, and the optimal hydrothermal treatment time for the formation of hollow microsphere is 24 h. Furthermore, the feasible growth mechanism for hollow microsphere was elaborated. Enriched oxygen vacancies (OVs) are introduced into BiOV₄ prepared with SDBS, largely elevating the separation efficiency of photo-generated charges. Under visible light irradiation, the photocatalytic activities of BiOV₄ for destruction of rhodamine (RhB) were evaluated. The photocatalytic degradation rate constant of RhB on the 3SBVO is 2.23 times of that on the blank BiOV₄ as the mass ratio of SDBS/BiOV₄ is 3 %. Photocatalytic degradation mechanism of BiVO₄ toward detoxification of organic pollutants was presented.

Antibiotics degradation by advanced oxidation process (AOPs): Recent advances in ecotoxicity and antibiotic-resistance genes induction of degradation products

Antibiotic contamination could cause serious risks of ecotoxicity and resistance gene induction. Advanced oxidation processes (AOPs) such as Fenton, photocatalysis, activated persulfate, electrochemistry and other AOPs technologies have been proven effective in the degradation of high-risk, refractory organic pollutants such as antibiotics. However, due to the limited mineralization ability, a large number of degradation intermediates will be produced in the oxidation process. The residual or undiscovered ecological risks of degradation products are potential safety hazards and problems necessitating comprehensive studies. In-depth investigations especially on the full assessments of ecotoxicity and resistance genes induction capability of antibiotic degradation products are important issues in reducing the environmental problems of antibiotics. Therefore, this review presents an overview of the current knowledge on the efficiency of different AOPs systems in reducing antibiotics toxicity and antibiotic resistance.

Architecture of visible-light induced Z-scheme MoS2/g-C3N4/ZnO ternary photocatalysts for malachite green dye degradation

The synthesis of bilayer heterojunctions has received considerable attention recently. Fabrication of novel bilayer composites is of significant interest to improve their photocatalytic efficiency. In this study, molybdenum disulfide (MoS₂), a layered dichalcogenide material exhibiting unique properties, in combination with graphitic carbon nitride (g-C₃N₄), a carbon-based layered material, was fabricated with small amounts of zinc oxide (ZnO). Three composites, MoS₂/g-C₃N₄, MoS₂/ZnO, and MoS₂/g-C₃N₄/ZnO were prepared via a simple exfoliation method and characterized by various physicochemical methods. The Z-scheme charge transfer mechanism in the prepared ternary composite improves efficiency by inhibiting the recombination rate of electron-hole pairs. It has shown excellent performance in degrading a major water contaminant, malachite green (MG) dye, under visible light irradiation.

Photocatalytic performance of 3D engineered chitosan hydrogels embedded with sulfur-doped C3N4/ZnO nanoparticles for Ciprofloxacin removal: Degradation and mechanistic pathways

Ciprofloxacin, a biotoxic micropollutant, is ubiquitously found in the water environment, which is a global concern. This study developed polymeric S-C3N4/ZnO-Chitosan (indexed as SCZ-CH) hydrogels for degrading Ciprofloxacin. The SCZ-CH hydrogels provided the Ciprofloxacin degradation efficiencies of ~93% and ~69% in UV and visible lights, respectively, at optimum conditions (SCZ-CH hydrogels with 2 g/L SCZ, 20 mg/L initial concentration, pH 5, and room temperature). In addition, immobilized SCZ-CH hydrogels structures enable easy separation of the SCZ catalyst from water. The spectroscopic and microscopic analyses of SCZ-CH hydrogels show multifaceted properties, like high oxygen concentrations, crystallinity, stacked structure, high roughness, and improved bandgap energy, which are responsible for the enhanced photocatalytic activity. The effects of water matrix and experimental conditions on Ciprofloxacin degradation were also studied, which suggested that the catalyst dose and solution pH have significant effects on photocatalytic activity. SCZ-CH hydrogels have shown good mineralization efficiency (~98%) and reusability (up to 10 cycles) for Ciprofloxacin removal. Superoxide radicals played an essential role in the degradation of Ciprofloxacin. The Ciprofloxacin molecules get degraded by driving radicals through oxidation, defluorination, substitution, and breaking of the rings. The proposed SCZ-CH hydrogels can be effectively used at a large scale to treat micropollutants.