Binary Photocatalysts Research Articles

Boosted photogenerated carriers separation in FeP/Cu3P/ZnIn2S4 photocatalyst for highly efficient H2 evolution under visible light

The development of efficient photocatalysts with effective charge separation and numerous active sites is a key challenge in photocatalysis. ZnIn2S4 based binary and ternary composite photocatalysts were successfully synthesized using microwave hydrothermal and calcination techniques, exhibiting excellent hydrogen production capabilities. Among these, the FeP/Cu3P/ZnIn2S4 composite photocatalysts demonstrated the highest hydrogen production performance, with an average rate of 1.613 mmol g−1 h−1, which was 4.42 times greater than that of pure ZnIn2S4. The enhanced hydrogen production of the FeP/Cu3P/ZnIn2S4 photocatalysts was attributed to the establishment of a p-n heterojunction at the ZnIn2S4 interface. Furthermore, the presence of FeP lowered the hydrogen production barrier in the system and provided additional active sites for the catalytic reaction.

Construction of LDH-derived CoNiP modified W/Z-CdS homojunction for improved photocatalytic hydrogen evolution: Achieving broad solar light response and multiple phases charge transfer

Heterojunction engineering represents a robust strategy for accelerating carrier transfer, thereby enhancing the activity of photocatalytic hydrogen evolution. In this work, a series of innovative CoNiP@W/Z-CdS heterojunctions were prepared for the purpose of investigating the photocatalytic hydrogen evolution activity under visible light-driven. To achieve high efficiency, lamellar CoNiP was first synthesized through the phosphatisation of CoNi LDH precursor. Subsequently, the W/Z-CdS homojunction was in-situ grown on the CoNiP via the hydrothermal method, resulting in the formation of the CoNiP@W/Z-CdS homojunction/heterojunction. The hydrogen evolution rate of 3% CoNiP@W/Z-CdS composite reaches 60.6 mmol/g/h, which is 3.6 times, 7.0 times and 11.9 times higher than that of W/Z-CdS, W-CdS and Z-CdS, respectively. The enhanced photocatalytic performance of 3% CoNiP@W/Z-CdS can be attributed to the introduction of an ultra-thin CoNiP bimetallic phosphide as cocatalyst, which increases the specific surface area to provide a large number of active sites for the catalytic reaction, and broadens the absorption range of sunlight. In particular, the synergistic effect between homojunction and Schottky junction in 3% CoNiP@W/Z-CdS further accelerates separation and migration rate of double interfacial carriers, improving photocatalytic H2 rate. This work offers a new perspective for the rational design of three-phase binary photocatalysts with high activity and stability.

Z-scheme heterojunction TNCoPc/BiOBr nanomicrospheres for efficient photodegradation of tetracycline and rhodamine B: Degradation performance, intrinsic mechanism and degradation pathway studies

The natural ecosystem has been significantly jeopardized due to the misuse of organic dyes and antibiotics. To treat organic wastewater safely and efficiently, this study synthesized a binary composite photocatalyst TNCoPc/BiOBr, using a solvothermal method that involved loading cobalt tetranitro phthalocyanine onto BiOBr. The results of the catalytic performance tests indicated that the composites exhibited the capacity to degrade rhodamine B and tetracycline hydrochloride by 97.75 % and 78.37 %, respectively. Moreover, the composite exhibited good cyclic stability. Subsequent analytical characterization confirmed the formation of a Z-scheme heterojunction, resulting in a synergistic effect. This Z-scheme heterojunction facilitated the capacity of photocatalyst to achieve enhanced light absorption, augmented photogenerated carrier separation efficiency, and augmented redox capacity. Additionally, theoretical calculations were employed to further elucidate the catalytic mechanism and synergistic effects. The results demonstrate that the Co-N4 sites are the active center of the TNCoPc and verify the contribution of nitro substitution to the photogenerated electron transfer mechanism on TNCoPc. Furthermore, a systematic degradation pathway was predicted and deduced based on Fukui indices and liquid chromatography-mass spectrometry data. This study presents a paradigm for the application of composite photocatalysts containing substituted phthalocyanines in the degradation of organic wastewater.

Zeolitic imidazolate framework-67/barium zirconate titanate nanocomposite, Part I: Synthesis, characterization, and boosted photocatalytic activity

Using BaTi0.85Zr0.15O3/ZIF-67 (BTZ/ZIF-67) nanocomposite, tetracycline (TC) was photodegraded. Characterization of the samples was carried out using a variety of techniques, including XRD, FESEM-EDS (Field Emission Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy), FT-IR (Fourier Transform Infra-Red), TEM (Transmission Electron Microscopy), BET (Brunauer-Emmett-Teller), BJH (Barrett-Joyner-Halenda), PL (Photoluminescence), TG-DTG (Thermogravimetry and Derivative Thermogravimetry), and UV–Vis DRS (Diffuse Reflectance Spectroscopy). BTZ/ZIF-67 nano-composites were synthesized using a one-step co-precipitation method. BTZ (30 %wt)/ZIF-67 showed the most impressive photocatalytic ability among the binary photocatalysts. Averaging the crystallite sizes of the nanocomposite samples identified by Scherrer and Williamson-Hall methods was 43.3 nm and 65.0 nm, respectively. The pHpzc values of samples of BTZ and BTZ (30 %wt)/ZIF-67 were approximately 6.7 and 10.0, respectively. Using the proposed method, we measured 357, 414, and 377 nm absorption edges for ZIF-67, BTZ, and BTZ (30 %wt)/ZIF-67 samples, which correspond to 3.47, 2.99, and 3.28 eV bandgap energies, respectively. The specific surface areas of BTZ, ZIF-67, and BTZ (30 %wt)/ZIF-67 nanocomposite are 122.15, 1218, and 1509 m2g−1, respectively. Under optimum conditions (0.8 g/L of the catalyst, CTC: 30 mg/L, and a pH 5), 89.5 % of total organic carbon (TOC) was removed within 180 min. Compared to BTZ photocatalyst, the BTZ (30 %wt)/ZIF-67 nanocomposite has a significantly larger surface area, thus enhancing photocatalytic activity. A synergistic effect was observed in the photodegradation of TC under Hg-lamp irradiation with the proposed BTZ/ZIF-67 composite. It is possible to alter the photocatalytic activity of the catalyst by changing the BTZ (30 %wt)/ZIF-67 ratio.

Synergistic photocatalytic activity of Bi2O3/g-C3N4/ZnO ternary heterojunction with dual Z-scheme charge transfer towards textile dye degradation

It is clear that a wide range of organic substances, including synthetic textile dyes, have the potential to negatively impact the environment. It is crucial to rationally develop highly effective photocatalysts for the degradation of such type of pollutants. In this regard, a heterostructured photocatalyst comes with enhanced charge separation and extended light absorption ability that improves photocatalytic performance. Therefore, In this study, a Bi2O3/g-C3N4/ZnO (BCNZ) ternary heterojunction photocatalyst was synthesized for the degradation of methylene blue (MB) textile dye.. Thermal polycondensation method was opted to synthesize g-C3N4, while ZnO and Bi2O3 photocatalysts were fabricated using co-precipitation method. Similarly, ternary heterojunction of BCNZ was constructed through co-precipitation method. The ternary heterojunction photocatalyst demonstrated better photodegradation ability due to dual Z-scheme charge transfer route. The dual Z-scheme heterojunction enabled the ternary heterojunction to exhibit enhanced light absorption capabilities with reduced recombination rates as well as enhanced charge separation and migration efficiency (confirmed via transient photocurrent response) that resulted in improved photocatalytic performance. The BCNZ dual Z-scheme photocatalyst displayed 92 % of degradation efficiency which was much higher than that of other (binary and pristine) photocatalysts. Scavenging tests and electron spin resonance spectroscopy revealed the significant role of the •O2−, and •OH radicals in the photodegradation of MB. Furthermore, the reusability test presented good stability and recyclability of the ternary photocatalyst with 80 % degradation efficiency after five catalytic cycles.

In-situ construction of 3D/2D ZnIn2S4/Ni-MOLs: Highly efficient visible-light-driven photocatalytic heterojunction in hydrogen evolution

Photocatalytic water splitting for hydrogen production is a sustainable and environmentally friendly technology. However, the rapid recombination of photo-induced electrons and holes results in low hydrogen production activity of photocatalysts. Constructing low-cost and high-efficiency heterojunctions is an imperative strategy to address the current challenges in photocatalytic hydrogen production. This study presents a novel binary heterojunction photocatalyst constructed of ZnIn2S4 nanoflowers and Ni-MOLs nanosheets, which was successfully synthesized via an in-situ hydrothermal method. Furthermore, the ZnIn2S4/Ni-MOLs heterojunction exhibited an excellent visible light absorption performance, which was conducive to hydrogen production under visible light irradiation. Specifically, the optimized ZnIn2S4/Ni-MOLs exhibited a remarkable hydrogen evolution rate of 4.75 mmol·g−1·h−1 under visible light irradiation, which was about 95 times and 8 times higher than that of pure Ni-MOLs and ZnIn2S4, respectively. Additionally, the catalyst exhibited excellent stability in five recycling cycles test, and the apparent quantum efficiency (AQE) of the optimized ZnIn2S4/Ni-MOLs had reached 23.3 %. The formation of the ZnIn2S4/Ni-MOLs heterojunction significantly enhanced photocatalytic activity by promoting efficient charge carrier separation, exposing more active sites and enhancing absorption of visible light. The experimental characterization and density functional theory (DFT) calculations revealed that the synergistic effect within the ZnIn2S4/Ni-MOLs heterojunction significantly facilitated the directional transfer of electrons from ZnIn2S4 to Ni-MOLs, achieving efficient charge carrier separation. This study not only synthesized an efficient photocatalyst for hydrogen production under visible light but also provided a novel strategy for constructing effective and stable ZnIn2S4-based or MOLs-based heterojunction photocatalysts.

One-pot hydrothermal synthesis of g-C3N4/BiOBr/Bi2MoO6 as a Z-scheme heterojunction for efficient photocatalytic degradation of ciprofloxacin (CIP) antibiotic and Rhodamine B (RhB) dye

Photocatalytic degradation of toxic organic pollutants using natural sunlight is a rapidly advancing area of research, particularly involving binary or ternary component photocatalysts with Z-type heterojunctions. In this study, ternary g-C3N4/BiOBr/Bi2MoO6 photocatalysts were fabricated using a simple one-pot solvothermal method. The morphology and physicochemical properties of the samples were characterized using various techniques, including X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), confirming the presence of BiOBr, Bi2MoO6, and g-C3N4 components. The inclusion of g-C3N4 increased the BET surface area of the composite up to 46 m2/g, compared with BiOBr. In addition, g-C3N4 also enhanced the light absorption capability of the composite into the visible light range, while BiOBr and Bi2MoO6 significantly improved separation of electron-hole pairs, as evidenced by photoluminescence (PL) intensity. Under visible light illumination (LED lamp), the prepared photocatalyst showed high efficiency, achieving 94 % degradation of ciprofloxacin (CIP) antibiotic in 180 min and 92 % degradation of Rhodamine B (RhB) dye in 240 min. Moreover, under natural sunlight irradiation, the photocatalyst achieved degradation efficiencies of approximately 91 % for CIP and 100 % for RhB within 180 minutes. The photodegradation of the pollutants followed first-order kinetics with a Z-scheme type heterojunction. The photogenerated electrons played a crucial role as the main active species involved in detoxification of the organic contaminants. The photocatalyst exhibited excellent structural stability and good cycling ability, maintaining its original photocatalytic performance even after five cycles of use. This work demonstrates a promising strategy for developing sunlight-active ternary heterojunctions for environmental remediation.

Hydrothermal synthesis and characterization of 0D/2D SrMoO4/g-C3N4 composite with direct Z-scheme heterojunction: Efficient photocatalytic Ciprofloxacin degradation

Ciprofloxacin (Cip) is a common pollutant that causes sewage problems, and its effective removal is a great contribution to the clean water environment. Direct Zener-scheme (Z-scheme) heterojunction photocatalyst is a promising design idea for the removal of residual antibiotics in water. The goal of this study is to construct a binary composite photocatalyst with Z-scheme heterojunction to effectively remove residual ciprofloxacin in wastewater. Herein, a direct Z-scheme 0D/2D SrMoO4/g-C3N4 (SMOCN) composite photocatalyst was synthesized by ultrasonic-assisted hydrothermal way and its interior information (chemical structure, micromorphology, and physic-optical property) was detected by various characterization instruments (XRD, FT-IR, EDX, XPS, UV–Vis DRS, and PL). Meanwhile, the photocatalytic activity of all-prepared catalysts were estimated by Cip photodegradation experiments under simulated sunlight (500 W Xenon lamp). Among them, 89.9 % of Cip was broken down by 30SMOCN composite within 180 min at pH 7.0, which respectively reached 2.56 times of bare SMO and 2.03 times of bare CN. Furthermore, 85.2 % of Cip targeted molecule is still removed by SMOCN (excellent stability and recyclability) after five cycle runs. Finally, the reasonableness of SMOCN conforming to the direct Z-scheme mechanism is verified by comparison of optical properties, quenching experiment results and photogenerated carrier migration paths: 1) There is optical complementarity between SMO and CN, which is represented by redshifted absorption edge, narrowed band gap and weaken PL intensity. 2) The key active site on the SMOCN composite surface is photogenerated carriers in Cip photocatalytic degradation, which given full play to the direct synergistic catalytic effect between SMO and CN heterojunction. 3) The direct Z-scheme mechanism preserves the carriers of SMOCN with effective photo-redox function, promotes their separation and prolongs their lifetime.

Novel green CQDs/ZnO binary photocatalyst synthesis for efficient visible light irradiation of organic dye degradation for environmental remediation

The advancement of effective and sustainable water treatment depends on the creation of a highly active and controllable photocatalyst. A suitable site for increasing the activity of such a photocatalyst is the heterojunction. Organic dyes have become a major source of concern in recent years because they are so common in wastewater. Heavy metals have a high permanence in wastewater and may be carcinogenic. Low-waste, high-performance technologies are needed to remove organic dyes and heavy metals from wastewater. To determine their structural, photochemical, and optical properties, Carbon Quantum Dots (CQDs) (made from Tamarindus indica shell waste), ZnO (from Ficus Benghalensis), and CQDs/ZnO photocatalysts were synthesised using green route techniques, followed by calcination. Malachite Green (MG) and Methylene Blue (MB) are effectively photo-degraded by the synthesised CQDs, ZnO, and Green CQDs/ZnO Binary Photocatalyst under the irradiation of naturally occurring solar light. The maximum photocatalytic activity for MG and MB within 60 min was shown by the Green CQDs/ZnO Binary Photocatalyst, with 100 % and 100 %, respectively. The reduced rate of electron-hole recombination causes effective photocatalytic activity. According to experiments with free radical entrapment, O2 and h+ play an important role in photodegradation. The study thus presents a fresh approach to the synthesis of highly effective binary photocatalysts for their application in environmental remediation.

Sodium titanate nanostructured modified by green synthesis of iron oxide for highly efficient photodegradation of dye contaminants

Abstract In this study, sodium titanate (ST)/iron oxide (Fe2O3) was successfully prepared as a novel binary photocatalyst for the first time to enhance the photocatalytic activity. The prepared photocatalyst was used in the photodegradation of methylene blue (MB) dye under sunlight and a tungsten lamp. The green synthesis method using orange peel extract was employed to prepare Fe2O3, while the hydrothermal method was used to synthesize ST. To achieve optimal photocatalytic efficiency, the loading of Fe2O3 onto ST was carefully controlled. The average crystallite size of ST, Fe2O3, and ST@Fe2O3 (with a 1:1 wt% ratio) was 999.8, 81.9, and 104 nm, respectively, using the Williamson–Hall (W–H) model. Optical analysis revealed that ST@Fe2O3 had a smaller direct bandgap (2.54 eV) compared to ST@0.3 Fe2O3 (2.70 eV) and ST@0.5 Fe2O3 (3.24 eV). The photodegradation of MB was analyzed considering the weight of the photocatalyst, the irradiation time, and the dye concentration. In-depth explanations of stability and kinetic models were also provided. Remarkably, the ST@Fe2O3 photocatalyst demonstrated superior performance compared to the other evaluated photocatalysts, completely degrading MB dye within just 60 min of solar light exposure. Incorporating Fe2O3 into ST effectively reduces the recombination of photo-produced electron/hole (e/h) pairs and broadens the response range of the solar spectrum. Based on these findings, ST@Fe2O3 appears to have a promising future as a practical photocatalyst for degrading various dye pollutants in wastewater.

Enhanced photocatalytic activity and antibacterial potential of a novel ternary ZnO-Ag2MoO4-AgI heterojunction photocatalyst

The construction of heterojunctions is a recognized strategy for enhancing photogenerated carrier separation. This research introduces a novel ZnO-Ag2MoO4-AgI photocatalyst with a double Z-type heterojunction, made using a straightforward precipitation technique. The precise position of energy levels endowed the ternary photocatalyst with the ability of directional electron flow, while the Z-type structure exhibits strong redox capabilities and facilitates the effective separation of photogenerated charge carriers. The structural characteristics, the photocatalytic activities, the antibacterial properties, and the cytotoxicity of the catalysts were evaluated. The results demonstrate that the catalytic ability of ternary composites work synergistically, surpassing the individual and binary photocatalysts. Notably, the ternary composites with 30 % AgI content exhibit the highest catalytic activity, achieving complete degradation of Rhodamine B in 30 minutes, and up to 71.2 % degradation of Norfloxacin in 60 minutes. Furthermore, more than 99.998 % of Staphylococcus aureus, and 100 % of Escherichia coli were eliminated within 40 minutes, while Human colorectal adenocarcinoma epithelial cells mortality reached 91.98 % at a dose of 250 μg/mL. Our study underscores the potential of this strategy for photocatalytic degradation of organic contaminants, and as an antibacterial agent, providing innovative insights into the design of ZnO-based heterostructure photocatalysts.

Efficient and economically affordable TiO2 nanotube-based ternary photocatalysts for CO2 conversion boosted by NiO nanoparticles and carbon quantum dots

Photocatalytic CO2 conversion, in general, requires the incorporation of expensive and noble materials to achieve a highly efficient conversion rate. Herein, the TNT/NiO/CQD ternary nanocomposites without any expensive materials and material modification are fabricated for the demonstration of efficient and economically affordable photocatalytic CO2 conversion, to our best knowledge, for the first time. The TNT-based ternary photocatalysts are successfully prepared by a simple anodization and immersion process. The TNT/NiO/CQD ternary nanocomposites produce 1.47 μmol·cm-2·h-1 (≈c.a. 2834 μmol·g-1·h-1) of CH4 as the sole product under AM 1.5 illumination. This is five times higher performance than that of bare TNT and the performance is comparable to that of any other TiO2-based unitary, binary, or ternary photocatalysts. This highly enhanced performance results from effective junction formation between TNT and NiO NP, and the dual role of CQDs as a light absorber and charge transporter/collector in the system. The formation of Z-scheme at the TNT/NiO interface leads to efficient charge transfer via a TiO2/NiO bond. The light absorption of the photocatalysts is enhanced and extended by decorated CQDs due to their small band gap. The charge transfer and collection are further improved by charge depletion at the TNT/CQD interface and the charge transfer at the NiO/CQD interface. This work provides a possible model for the realization of efficient and economically affordable photocatalytic CO2 conversion.

An investigation on the visible light-driven Z-scheme BiVO4/g-C3N4 heterostructures: Performance, evaluation, and mechanism for dye and antibiotics degradation

Herein, the novel and efficient yellow BiVO4/g-C3N4 (BCN) binary composite photocatalyst was successfully fabricated via a simple ultrasonicated-assisted approach for the enhanced photocatalytic removal of methylene blue, tetracycline hydrochloride and ciprofloxacin under simulated visible irradiation. The crystal structure, composition, morphology, textural, optical, and electrochemical properties of the catalysts were comprehensively analyzed. The fishbone-liked BiVO4 were uniformly dispersed on the nano-layered g-C3N4, which not only contributed to the red-shift in the adsorption range but also suppressed the recombination of generated electron-holes. The stable photocurrent of BCN21 with a BiVO4/g-C3N4 mass ratio of 2:1 is higher than that of pristine BiVO4 and g-C3N4. The degradation experiments indicated that the BCN21 exhibited an outstanding photocatalytic removal rate for TC, which was 2.4 and 1.7 times as much as that of the pristine g-C3N4 and BiVO4, respectively. BCN21 also performed an excellent MB discoloration ability (up to 94 % within 180 min). It also showed superior ciprofloxacin degradation rates (3 and 4 times higher than pristine g-C3N4 and BiVO4). Both •O2, •OH, and h+ are involved in the photocatalytic degradation of TC, and that •O2 plays the most crucial role. Moreover, the cyclic experiments proved that the BCN21 possesses good stability after five consecutive runs with no obvious deactivation observed. Overall, this present study provides an insightful strategy for the development of heterojunction photocatalysts towards practical environmental purification.

BaTi0.85Zr0.15O3/MOF-5 nanocomposite: Synthesis, characterization and photocatalytic activity toward tetracycline

It has been proposed that oriented anchoring strategies can be used to organize BaTi0.85Zr0.15O3 (BTZ) quantum dots (QD) with MOF-5 to provide highly efficient catalytic degradation of tetracycline (TC). This study presents the preparation of [Zn4O (BDC)3] (BDC = benzene-1,4dicarboxylate) metal–organic framework-5 (MOF-5)/BTZ nanocomposites by a facile one-pot solvent-thermal precipitation method. The as-synthesized samples were identified by XRD, TG-DTG, UV–VIS DRS, FESEM, FTIR, BET, TEM, PL, and EDX characterization techniques. The photocatalytic ability of nanocomposite BTZ (30 %wt)/MOF-5 was particularly impressive among the binary photocatalysts. In a 10 ppm solution of TC, BTZ (30 wt%)/MOF-5 demonstrated superior photodegradation activity, with 95 % degradation efficiency of TC determined by HPLC. The best response was achieved at pH 11 with catalyst dosages of 0.2 g/L, irradiation time of 150 min, and CTC of 10 ppm. An internal electric field was suggested to mediate the direct Z-scheme charge transfer mechanism between BTZ and MOF-5. The improvement was achieved by fabricating BTZ and MOF-5 in an indirect Z-scheme heterojunction system. Photogenerated electron-hole separation can be accelerated by BTZ/MOF-5 with improved redox capabilities. Overall, taking advantage of an enhanced redox capacity under ultraviolet (UV) light irradiation, this study demonstrates how to promote efficient antibiotic degradation using MOF-based nanocomposites. Moreover, photodegradation kinetics were studied using the Hinshelwood formula, giving 0.0113 min−1 (slope) and 61.32 min as t1/2. In the COD experiment, mineralized TC molecules had y = -0.0144 + 0.0444x, r2 = 0.9942, and k = 0.0144 min−1 (t1/2 = 48.12 min).

Enhanced efficiency of AgAlO2/g-C3N4 binary composite to degrade organic pollutants for environmental remediation under visible light irradiation

This study explores the utilization of semiconductor-based photocatalysts for environmental remediation through photocatalytic degradation, harnessing solar energy for effective treatment. The primary focus is on the application of photocatalytic technology for the degradation of 2-chlorophenol and methylene blue, critical pollutants requiring remediation. The research involves the synthesis of binary AgAlO2/g-C3N4 nanocomposites through an exchange ion method, subsequent calcination, and sonication. This process enhances the transfer of photogenerated electrons from AgAlO2 to g-C3N4, resulting in a significantly increased reductive electron charge on the surface of g-C3N4. The photocatalytic activity of the synthesized composites is comprehensively examined in the degradation of 2-chlorophenol and methylene blue through detailed crystallographic, electron-microscopy, photoemission spectroscopy, electrochemical, and spectroscopic characterizations. Among the various composites, AgAlO2/20% g-C3N4 emerges as the most active photocatalyst, achieving an impressive 98% degradation of methylene blue and 97% degradation of 2-chlorophenol under visible light. Notably, AgAlO2/20% g-C3N4 surpasses bare AgAlO2 and bare g-C3N4, exhibiting 1.66 times greater methylene blue degradation and constant rate (k) values of 20.17 × 10−3 min−1, 4.18 × 10−3 min−1 and 3.48 × 10−3 min−1, respectively. The heightened photocatalytic activity is attributed to the diminished recombination rate of electron-hole pairs. Scavenging evaluations confirm that O2•− and h+ are the primary photoactive species steering methylene blue photodegradation over AgAlO2/g-C3N4 in the visible region. These findings present new possibilities for the development of efficient binary photocatalysts for environmental remediation.

Low-cost ternary composite photocatalysts consisting of TiO2, kaolinite and cement for an efficient organic waste decontamination in water

The present study demonstrates the fabrication of heterogeneous ternary composite photocatalyst consisting of TiO2, kaolinite and cement (TKCe), which is essential to overcome the practical barriers that are inherent to currently available photocatalysts. TKCe is prepared via a cost-effective method, which involved the mechanical compression and thermal activation as a major fabrication steps. Clay-cement ratio primarily determines TKCe mechanical strength and photocatalytic efficiency where TKCe with the optimum clay-cement ratio, which is 1:1 results in uniform matrix with fewer surface defects. The composites that have clay-cement ratio below or above the optimum ratio account for comparatively low mechanical strength and photocatalytic activity due to inhomogeneous surface with more defects, including particle agglomeration and cracks. The TKCe mechanical strength is mainly from clay-TiO2 interactions and TiO2-cement interactions. TiO2-cement interactions result in CaTiO3 formation, which significantly increases matrix interactions; however, the maximum composite performance is observed at the optimum titanate level; anything above or below this level deteriorates composite performance. Over 90% degradation rates are characteristic to all TKCe, which follow pseudo first order kinetics in methylene blue decontamination. The highest rate constant is observed with TKCe 1-1, which is 1.57 h−1 and being the highest among all the binary composite photocatalyst that were fabricated previously. The TKCe 1-1 accounts for the highest mechanical strength, which is 6.97 MPa, while the lowest is observed with TKCe 3-1, indicating that clay-cement ratio has direct relation to composite strength. TKCe is a potential photocatalyst, which can be obtained in variable sizes and shapes, complying with real industrial wastewater treatment requirements.

TiO2 nanorod decorated with MoS2 nanospheres: An efficient dual-functional photocatalyst for antibiotic degradation and hydrogen production

The design and preparation of dual-functional photocatalysts for simultaneously realizing photocatalytic wastewater purification and hydrogen energy generation pose significant challenges. This article presents the engineering of a binary heterostructured photocatalyst by combining TiO2 (nanorods) and MoS2 nanosphere using a straightforward solvothermal method and the assessment of the phase structures, morphologies, and optical properties of the resulting nanocomposites using diverse analytical techniques. The TiO2(Rod)/MoS2 composite exhibits remarkable efficacy in degrading ciprofloxacin, achieving 93% removal rate within 1 h, which is four times higher than that of bare TiO2. Moreover, the optimized TiO2(Rod)/MoS2 presents an outstanding hydrogen production rate of 7415 μmol g−1, which is ∼24 times higher than that of pristine TiO2. Under UV–visible light irradiation, the TiO2(Rod)/MoS2 heterojunction displays an exceptional photocatalytic performance in terms of both photodegradation and hydrogen production, surpassing the performance of TiO2 particle/MoS2. The study findings demonstrate that TiO2(Rod)/MoS2 nanocomposites exhibit considerably improved photocatalytic degradation and hydrogen generation activities. Based on the experimental results, a possible mechanism is proposed for the transfer and separation of charge carriers in Z-scheme heterojunctions.

A facile synthesis of metal vanadate incorporated with metal oxide/rare earth metal oxide composite for photocatalytic application

In this work (Ag2O/BiVO4) binary and (Ag2O/BiVO4/Eu2O3) ternary heterojunction photo-catalysts have been synthesized through a hydrothermal technique for the purpose of photocatalytic degradation of hazardous dyes. The facile synthesized composites of (Ag2O/BiVO4) and (Ag2O/BiVO4/Eu2O3)have been prepared using a hydrothermal process. The synthesized composites used to degrade the Methylene blue and Congo-red dyes under sunlight. The X-ray diffraction confirms the crystalline structure of synthesized composites. The calculated crystalline sizes for (Ag2O/BiVO4) and (Ag2O/BiVO4/Eu2O3) are 9.9 nm and 2.84 nm respectively. The morphology of samples has been analyzed by SEM while the absorption spectrum and bonding of molecules were observed using FTIR in the range of 600–4000 cm−1. The elemental percentage of synthesized material is determined by using EDX spectroscopy and UV spectroscopy used to study optical properties. Using Tauc plot calculated band gap of (Ag2O/BiVO4)is 1.84 eV and (Ag2O/BiVO4/Eu2O3) is 1.65 eV. The degradation efficiency of composites(Ag2O/BiVO4) (Ag2O/BiVO4/Eu2O3) towards a dye MB is 38% and 41% respectively, while these composites were found to degrade the dye CR 82% and 99%respectively in the exposure of sunlight. Both synthesized composites showed excellent %age degradation toward acidic dye (CR). The outcomes of synthesized composites indicates that suitable optical absorption, better segregation of charge carries and reduction of electron-hole recombination these factor effectively contribute to enhance photocatalytic activity towards acidic dye CR.

Amine functionalized graphene oxide decorated with ZnO-WO3 nanocomposites for remediation of organic dye from wastewater

Photocatalytic degradation is as an efficient technique to eradicate toxic chemical pollutants from contaminated water sources. However, the selectivity and photocatalytic activity are the challenging targets to explore the new photocatalysts. Therefore, our research goal is to develop a suitable photocatalyst to satisfy the recent photocatalytic degradation demand. In this work, amine functionalized graphene oxide (NH2-GO) supported heterojunction ternary novel nanocomposites (NH2-GO/ZnO-WO3) were prepared via simple solvothermal method. Structural and morphological investigations of the prepared composites are systematically observed by Field Emission Scanning Electron Spectroscopy (FE-SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and Ultraviolet–Visible (UV–vis) Spectroscopy. FT-IR analysis confirmed the effective functionalization of amine on graphene oxide. The XRD results indicated that the prepared nanocomposites were free from any impurities and the binary composite (NH2-GO/ZnO) showed hexagonal wurtzite structure, whereas the ternary composite (NH2-GO/ZnO-WO3) exhibited mix crystal structure of monoclinic and hexagonal phase of WO3 and ZnO, respectively. The synthesized ternary photocatalyst (NH2-GO/ZnO-WO3) demonstrated superior photocatalytic efficiency towards various organic dyes such as cationic dye methylene blue (MB, 85.89%) and anionic dye methyl orange (MO, 60.98%) compared to binary photocatalyst (NH2-GO/ZnO) that showed only 52.28% of MB and 25.8% of MO dye degradation under UV light irradiation. The enhanced photocatalytic performance was mainly due to the low recombination rate of photogenerated electron-hole pair, narrow band gap, and large surface area of ternary composite. The presence of lone pair electrons in amino group provides a negative-charged surface composite resulting good interaction with cationic dye is the key to upgrade the photocatalytic performance. The ternary nanocomposite NH2-GO/ZnO-WO3 has the capacity to be a competent and acceptable photocatalyst for the photodegradation of organic dyes used in industries.

Removal of Emerging Organic Pollutants by Zeolite Mineral (Clinoptilolite) Composite Photocatalysts in Drinking Water and Watershed Water

One of the most challenging problems for people around the world is the lack of clean water. In the past few decades, the massive discharge of emerging organic pollutants (EOPs) into natural water bodies has exacerbated this crisis. Considerable research efforts have been devoted to removing these EOPs due to their biotoxicity at low concentrations. Heterogeneous photocatalysis via coupling clay minerals with nanostructured semiconductors has proven to be an economical, efficient, and environmentally friendly technology for the elimination of EOPs in drinking water and watershed water. Natural zeolite minerals (especially clinoptilolites) are regarded as appropriate supports for semiconductor-based photocatalysts due to their characteristics of having a low cost, environmental friendliness, easy availability, co-catalysis, etc. This review summarizes the latest research on clinoptilolites used as supports to prepare binary and ternary metal oxide or sulfide semiconductor-based hybrid photocatalysts. Various preparation methods of the composite photocatalysts and their degradation efficiencies for the target contaminants are introduced. It is found that the good catalytic activity of the composite photocatalyst could be attributed to the synergistic effect of combining the clinoptilolite adsorbent with the semiconductor catalyst in the heterogeneous system, which could endow the composites with an excellent adsorption capacity and produce more e−/h+ pairs under suitable light irradiation. Finally, we highlight the serious threat of EOPs to the ecological environment and propose the current challenges and limitations, before putting the zeolite mineral composite photocatalysts into practice. The present work would provide a theoretical basis and scientific support for the application of zeolite-based photocatalysts for degrading EOPs.