Hydrothermal growth of ZnCdS/TiO2 nanoparticles on the surface of the Ti3C2 MXene sheet to enhance photocatalytic performance under visible light

Ternary tin-doped titanium dioxide/calcium oxide (Sn-TiO2/CaO) composite as a photocatalyst for efficient removal of toxic dyes

In this study, a novel environmentally friendly route was explored for the synthesis of a tin-doped titanium dioxide/calcium oxide (Sn-TiO2/CaO) composite using eggshell as a ternary photocatalyst. The composite was prepared via a simple hydrothermal method, resulting in a unique material with potential applications in photocatalysis. The prepared photocatalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, UV-vis/diffuse reflectance spectroscopy, scanning electron microscopy, X-ray fluorescence, and the Brunauer-Emmett-Teller techniques. At the same time, the Sn-TiO2/CaO composite shows excellent degradation activity for toxic dyes. The degradation efficiencies for alizarin red, bromophenol blue, methylene blue, malachite green, and methyl red are 68.38%, 62.39%, 76.81%, 86.93%, and 17.52%, respectively, under ultraviolet light irradiation for 35 min at pH = 3. In addition, the best photocatalytic degradation efficiency for zero charge (pH 7) and basic pH is for AR 98.21% and 68.38%, MR 33.01% and 17.52%, BPB 73.17% and 17.52%, MB 72.32% and 76.81%, and MG 85.59% and 86.93%, respectively, under UV light irradiation for 35 min. The increase in photocatalytic activity of the ternary photocatalyst is accredited to the enhancement of electron-hole pair separation. Simultaneous photodegradation and photoreduction of organic dyes show that ternary photocatalysts could be used in real wastewater applications.

Synergistic doping with Ag, CdO, and ZnO to overcome electron-hole recombination in TiO2 photocatalysis for effective water photo splitting reaction

This manuscript is dedicated to a comprehensive exploration of the multifaceted challenge of fast electron-hole recombination in titanium dioxide photocatalysis, with a primary focus on its critical role in advancing the field of water photo splitting. To address this challenge, three prominent approaches-Schottky barriers, Z-scheme systems, and type II heterojunctions-were rigorously investigated for their potential to ameliorate TiO2's photocatalytic performance toward water photo splitting. Three distinct dopants-silver, cadmium oxide, and zinc oxide-were strategically employed. This research also delved into the dynamic interplay between these dopants, analyzing the synergetic effects that arise from binary and tertiary doping configurations. The results concluded that incorporation of Ag, CdO, and ZnO dopants effectively countered the fast electron-hole recombination problem in TiO2 NPs. Ag emerged as a critical contributor at higher temperatures, significantly enhancing photocatalytic performance. The photocatalytic system exhibited a departure from Arrhenius behavior, with an optimal temperature of 40°C. Binary doping systems, particularly those combining CdO and ZnO, demonstrated exceptional photocatalytic activity at lower temperatures. However, the ternary doping configuration involving Ag, CdO, and ZnO proved to be the most promising, surpassing many functional materials. In sum, this study offers valuable insights into how Schottky barriers, Z-scheme systems, and type II heterojunctions, in conjunction with specific dopants, can overcome the electron-hole recombination challenge in TiO2-based photocatalysis. The results underscore the potential of the proposed ternary doping system to revolutionize photocatalytic water splitting for efficient green hydrogen production, significantly advancing the field's understanding and potential for sustainable energy applications.

In Situ Growth of CdZnS Nanoparticles@Ti3C2Tx MXene Nanosheet Heterojunctions for Boosted Visible-Light-Driven Photocatalytic Hydrogen Evolution

Using natural light energy to convert water into hydrogen is of great significance to solving energy shortages and environmental pollution. Due to the rapid recombination of photogenerated carriers after separation, the efficiency of photocatalytic hydrogen production using photocatalysts is usually very low. Here, efficient CdZnS nanoparticles@Ti3C2Tx MXene nanosheet heterojunction photocatalysts have been successfully prepared by a facile in situ growth strategy. Since the CdZnS nanoparticles uniformly covered the Ti3C2Tx Mxene nanosheets, the agglomeration phenomenon of CdZnS nanoparticles could be effectively inhibited, accompanied by increased Schottky barrier sites and an enhanced migration rate of photogenerated carriers. The utilization efficiency of light energy can be improved by inhibiting the recombination of photogenerated electron-hole pairs. As a result, under the visible-light-driven photocatalytic experiments, this composite achieved a high hydrogen evolution rate of 47.1 mmol h-1 g-1, which is much higher than pristine CdZnS and Mxene. The boosted photocatalytic performances can be attributed to the formed heterojunction of CdZnS nanoparticles and Ti3C2Tx MXene nanosheets, as well as the weakened agglomeration effects.

Efficient activation of persulfate by Ti3C2 MXene QDs modified ZnFe2O4 for the rapid degradation of tetracycline

Mxene-based catalysts with specific interfacial characteristics are beneficial for photocatalytic applications. Herein, Ti₃C₂ MXene modified ZnFe₂O₄ nanocomposite materials were prepared for photocatalysis. The morphology and structure of the nanocmposites were characterized by scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), which revealed that Ti₃C₂ MXene as quantum dots (QDs) was uniformly distributed on the ZnFe₂O₄ surface. The Ti₃C₂ QDs modified ZnFe₂O₄ catalyst (ZnFe₂O₄/MXene-15%) under visible light achieved 87% degradation efficiency of tetracycline within 60 min when coupled with persulfate (PS) system. The initial solution pH, PS dosage and co-existing ions were found to be the main factors affecting the heterogeneous oxidation process, while quenching experiments showed that O₂^•- is the main oxidizing species in the removal of tetracycline in ZnFe₂O₄/MXene-PS system. In addition, the cyclic experiments suggested that ZnFe₂O₄/MXene had good stability and thus it may have practical applications in industry.

Nanoarchitecture of a Ti3C2@TiO2 Hybrid for Photocatalytic Antibiotic Degradation and Hydrogen Evolution: Stability, Kinetics, and Mechanistic Insights

Designing of a visible-light-driven semiconductor-based heterojunction with suitable band alignment and well-defined interfacial contact is considered to be an effective strategy for the transformation of solar-to-chemical energy and environmental remediation. In this context, MXenes have received tremendous attention in the research community due to their merits of abundant derivatives, elemental composition, excellent metallic conductivity, and surface termination groups. Meanwhile, a facile synthetic strategy for MXene-derived TiO₂ nanocomposites with stable framework and higher photocatalytic activity under visible-light irradiation still remains a challenge for researchers. Herein, we report a novel synthetic strategy of preparing a two-dimensional Ti₃C₂@TiO₂ nanohybrid by a facile reflux method under acidic conditions. In this oxidation reaction, protonation of the hydroxyl terminal group of MXene creates Ti more electrophilic and susceptible to an oxidative nucleophilic addition reaction with the presence of both water and oxygen. The physicochemical properties of the nanohybrid Ti₃C₂@TiO₂ were verified by varieties of characterization techniques. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy analysis specifically elucidated the intimate interfacial interaction between Ti₃C₂ and TiO₂. The optimized Ti₃C₂@TiO₂-48 h photocatalyst exhibited the highest tetracycline hydrochloride (TCH, 90% in 90 min) degradation efficiency in comparison to pristine TiO₂ with a rate constant (k) of 0.02463 min^-1. The major contribution of ^•O₂^- and ^•OH radicals throughout photocatalytic TCH degradation was confirmed by the trapping experiment. Moreover, the photocatalyst showed the highest hydrogen generation rate of 140.8 μmol h^-1 along with an apparent conversion efficiency of 2.2%. The excellent photocatalytic activity of Ti₃C₂@TiO₂ originated from the superior electrical conductivity of cocatalyst Ti₃C₂, which facilitated spatial photogenerated e^-/h⁺ separation and transfer at the Ti₃C₂ MXene@TiO₂ interface. Overall, this research work will describe a promising protocol of designing MXene-derived photocatalysts toward efficient environmental remediation and wastewater treatment applications.

2D MXene-Based Biosensing: A Review

MXene emerged as decent 2D material and has been exploited for numerous applications in the last decade. The remunerations of the ideal metallic conductivity, optical absorbance, mechanical stability, higher heterogeneous electron transfer rate, and good redox capability have made MXene a potential candidate for biosensing applications. The hydrophilic nature, biocompatibility, antifouling, and anti-toxicity properties have opened avenues for MXene to perform in vitro and in vivo analysis. In this review, the concept, operating principle, detailed mechanism, and characteristic properties are comprehensively assessed and compiled along with breakthroughs in MXene fabrication and conjugation strategies for the development of unique electrochemical and optical biosensors. Further, the current challenges are summarized and suggested future aspects. This review article is believed to shed some light on the development of MXene for biosensing and will open new opportunities for the future advanced translational application of MXene bioassays.

Integration of Carbon Dots on Nanoflower Structured ZnCdS as a Cocatalyst for Photocatalytic Degradation

The application of catalysts is one of the most effective methods in the oil refining, chemical, medical, environmental protection, and other industries. In this work, carbon dots (CDs) were selected as an initiator and doped into the main catalyst, Zn_0.2Cd_0.8S, and a novel Zn_0.2Cd_0.8S@CD composite catalyst with a nanoflower structure was successfully obtained. The synthesized composites (Zn_0.2Cd_0.8S@CDs) were characterized by means of SEM, TEM, XRD, FT-IR, XPS, and UV-Vis DRS. Transient photocurrent response and Nyquist curve analysis further proved that the carrier separation efficiency of the composite catalyst was significantly improved. In addition, the photocatalytic activity of Zn_0.2Cd_0.8S@CDs for rhodamine B removal from aqueous solution was tested under visible-light irradiation. When the amount of Zn_0.2Cd_0.8S@CDs composite catalyst reached 50 mg, the degradation rate of rhodamine B was 79.35%. Finally, the photocatalytic degradation mechanism of the Zn_0.2Cd_0.8S@CDs complex was studied. CD doping enhances the adsorption capacity of Zn_0.2Cd_0.8S@CDs composite catalysts due to the increase in surface area, effectively inducing charge delocalization and enhancing the photocatalytic capacity. Zn_0.2Cd_0.8S@CDs composites with low cost and high carrier separation efficiency have broad application prospects in the photocatalytic degradation of dyes.

Advances in Titanium Carbide (Ti3C2T x ) MXenes and Their Metal-Organic Framework (MOF)-Based Nanotextures for Solar Energy Applications: A Review

Introducing new materials with low cost and superior solar harvesting efficiency requires urgent attention to solve energy and environmental challenges. Titanium carbide (Ti₃C₂T _x ) MXene, a 2D layered material, is a promising solution to solve the issues of existing materials due to their promising conductivity with low cost to function as a cocatalyst/support. On the other hand, metal-organic frameworks (MOFs) are emerging materials due to their high surface area and semiconducting characteristics. Therefore, coupling them would be promising to form composites with higher solar harvesting efficiency. Thus, the main objective of this work to disclose recent development in Ti₃C₂T _x -based MOF nanocomposites for energy conversion applications to produce renewable fuels. MOFs can generate photoinduced electron/hole pairs, followed by transfer of electrons to MXenes through Schottky junctions for photoredox reactions. Currently, the principles, fundamentals, and mechanism of photocatalytic systems with construction of Schottky junctions are critically discussed. Then the basics of MOFs are discussed thoroughly in terms of their physical properties, morphologies, optical properties, and derivatives. The synthesis of Ti₃C₂T _x MXenes and their composites with the formation of surface functionals is systematically illustrated. Next, critical discussions are conducted on design considerations and strategies to engineer the morphology of Ti₃C₂T _x MXenes and MOFs. The interfacial/heterojunction modification strategies of Ti₃C₂T _x MXenes and MOFs are then deeply discussed to understand the roles of both materials. Following that, the applications of MXene-mediated MOF nanotextures in view of CO₂ reduction and water splitting for solar fuel production are critically analyzed. Finally, the challenges and a perspective toward the future research of MXene-based MOF composites are disclosed.

Construction of 2D layered phosphorus-doped graphitic carbon nitride/BiOBr heterojunction for highly efficient photocatalytic disinfection

Infectious diseases caused by bacteria intimidate the health of human beings all over the world. Although many avenues have been tried, various operating conditions limit their actual applications. Photocatalytic nanomaterials are becoming candidates to be competent for water purification. Here, a novel and more efficient S-scheme has been engineered between two dimensional (2D) layered phosphorus-doped graphitic carbon nitride (P-g-C 3 N 4 ) and BiOBr via hydrothermal polymerization to inhibit the recombination of charge and broaden light absorption. The as-prepared P-g-C 3 N 4 /BiOBr hybrids exhibits significantly improved photocatalytic disinfection contrast to g-C 3 N 4 /BiOBr in visible wavelengths, suggesting phosphorus doping which adjusts the band structure plays a significant role in the S-scheme system. And the sterilization rate of multidrug-resistant Acinetobacter baumannii 28 ( AB 28 ) was 99.9999% within 80 min and Staphylococcus aureus ( S. aureus ) was 99.9%.