ZnCr-layered Double Hydroxide Research Articles

Synthesis of polyoxometalate-pillared Zn-Cr layered double hydroxides for photocatalytic CO2 reduction and H2O oxidation.

Polyoxometalate (POM)-pillared Zn-Cr layered double hydroxides (LDHs) exhibited high photocatalytic activities in CO2 reduction and H2O oxidation reactions. For CO2 reduction in pure water, the CO production was 1.17 μmol g-1 after a 24 h reaction. For O2 evolution in NaIO3 solution, the O2 production reached 148.1 μmol g-1 after a 6 hour reaction. A mechanism study indicated that the electron transfer from Zn-Cr LDHs to POMs (SiW12O404-) promoted photocatalytic activities.

Zn-Cr Layered Double Hydroxides for Photocatalytic Transformation of CO2 under Visible Light Irradiation: The Effect of the Metal Ratio and Interlayer Anion

Carbon dioxide is the main gas responsible for the greenhouse effect. Over the last few years, the research focus of many studies has been to transform CO2 into valuable products (CO, HCOOH, HCHO, CH3OH and CH4), since it would contribute to mitigating global warming and environmental pollution. Layered double hydroxides (LDHs) are two-dimensional materials with high CO2 adsorption capacity and compositional flexibility with potential catalytic properties to be applied in CO2 reduction processes. Herein, Zn-Cr LDH-based materials with different metal ratio and interlayer anions, i.e., chloride (Cl−), graphene quantum dots (GQDs), sodium dodecyl sulfate (SDS) and sodium deoxycholate (SDC), have been prepared by a co-precipitation method and characterized by different techniques. The influence of the interlayer inorganic and organic anions and the metal ratio on the application of Zn-Cr LDHs as catalysts for the photocatalytic CO2 reduction reaction under visible light irradiation is unprecedentedly reported. The catalytic tests have been carried out with Ru(bpy)32+ as photosensitizer (PS) and triethanolamine as sacrificial electron donor (ED) at λ = 450 nm. All LDHs materials exhibited good photocatalytic activity towards CO. Among them, LDH3-SDC showed the best catalytic performance, achieving 10,977 µmol CO g−1 at 24 h under visible light irradiation with a CO selectivity of 88%. This study provides pertinent findings about the modified physicochemical features of Zn-Cr LDHs, such as particle size, surface area and the nature of the interlayer anion, and how they influence the catalytic activity in CO2 photoreduction.

Electrochemical determination of vanillin using 2D/2D heterostructure based on ZnCr-layered double hydroxide and g-CN.

AZnCr-LDH@g-CN composite was synthesized through a one-pot hydrothermal method to fabricate an effective sensor for detecting vanillin. The prepared material was investigated by using structural and physical studies. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) with applied potential (Epa = + 0.68V vs Ag/AgCl) were used to examine the electrochemical behavior of vanillin. The fabricated electrode exhibited a linear detection range of 0.001-143.2μM, a low detection limit of 0.9nM, sensitivity of 4.72 µA µM-1cm-2, selectivity, stability, reproducibility (RSD = 4.40%), and repeatability (RSD = 4.46%). The optimized sensor was successfully applied to detect vanillin in real samples, including ice cream, chocolate, and water, and their recovery was 98.46-99.80%. Overall, the ZnCr-LDH@g-CN composite sensor offers a promising solution for precise vanillin detection.

Tuning the Interfaces of ZnO/ZnCr2 O4 Derived from Layered-Double-Hydroxide Precursors to Advance Nitrogen Photofixation.

Drawing inspiration from the enzyme nitrogenase in nature, researchers are increasingly delving into semiconductor photocatalytic nitrogen fixation due to its similar surface catalytic processes. Herein, we reported a facile and efficient approach to achieving the regulation of ZnO/ZnCr2 O4 photocatalysts with ZnCr-layered double hydroxide (ZnCr-LDH) as precursors. By optimizing the composition ratio of Zn/Cr in ZnCr-LDH to tune interfaces, we can achieve an enhanced nitrogen photofixation performance (an ammonia evolution rate of 31.7 μmol g-1 h-1 using pure water as a proton source) under ambient conditions. Further, photo-electrochemical measurements and transient surface photovoltage spectroscopy revealed that the enhanced photocatalytic activity can be ascribed to the effective carrier separation efficiency, originating from the abundant composite interfaces. This work further demonstrated a promising and viable strategy for the synthesis of nanocomposite photocatalysts for nitrogen photofixation and other challenging photocatalytic reactions.

Fabrication of CdS/ZnCr-LDH heterojunctions with enhanced of tetracycline hydrochloride photocatalytic degradation under visible light

Water pollution caused by antibiotics is one of the main problems facing mankind. Photocatalytic degradation is a green, thorough and effective method to remove antibiotics from wastewater, which has broad application prospects. In this study, a Z-scheme photocatalyst constructed by cadmium sulfide (CdS) and ZnCr-layered double hydroxide (ZnCr-LDH) was prepared by hydrothermal method. The properties of the photocatalysts were fully characterized and the photocatalytic performance were evaluated via degradation tetracycline hydrochloride (TCH) under visible light irradiation. The CdS/ZnCr-LDH-5 photocatalyst was very effective for the removal of TCH (84.9%), which is 4.7 times and 2.5 times than that of its precursor ZnCr-LDH and CdS, respectively. The enhanced degradation efficiency of CdS/ZnCr-LDH-5 photocatalyst can be attributed to the high redox ability and charge separation efficiency. Finally, possible degradation pathway and a Z-scheme degradation mechanism was proposed according to the liquid chromatography-mass spectrometry (LC-MS), radial trapping experiments and band energy structure, respectively. This work provides new sights for the design heterojunctions with a Z-scheme charge transfer mechanism for effective photocatalytic degradation antibiotics.

Efficient ZnCr LDH/monoclinic‐WO3 composites for Degradation of Tetracycline under Visible Light

AbstractRecently, efficient removal of antibiotics like Tetracycline (TC) from wastewater is emerging as a crucial problem. However, low adsorption capacity and high cost of photocatalysts limit their utility. In this context, monoclinic tungsten trioxide (WO3) loaded ZnCr layered double hydroxide (LDH) composites (ZnCr‐xWO3 x=10 and 20 %) are prepared by co‐precipitation method and characterized by several techniques viz. X‐Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman, Photoluminescence (PL), Field‐Emission Scanning Electron Microscopy (FE‐SEM), Brunauer Emmett Teller (BET), Diffuse Reflectance Spectroscopy (DRS) and Dynamic Light Scattering (DLS). The XRD pattern confirms the formation of ZnCr LDH and its composites with monoclinic‐WO3. Bond vibrations and phase transitions were explored with the help of FTIR and Raman spectra. The BET analysis for ZnCr LDH and ZnCr‐10WO3 composite shows surface area as 27.439 m2/g and 47.691 m2/g. The higher photocatalytic performance of the composites formed is due to enhanced specific surface area and better separation efficiency of photo‐generated electrons and holes through conventional class II hetero junction between ZnCr LDH and monoclinic‐WO3. The kinetics studies performed shows better fit for pseudo first order reaction with maximum degradation efficiency and rate constant for ZnCr‐10WO3 (i. e., 86.7 % and 1.5×10−2 min−1).

Graphitic-C3N4/ZnCr-layered double hydroxide 2D/2D nanosheet heterojunction: Mesoporous photocatalyst for advanced oxidation of azo dyes with in situ produced H2O2

In this study the constructional modification of Graphitic carbon nitride nanosheet (GCN-ns) has been made with the aid of ZnCr layered double hydroxide (ZC-LDH) in a unique 2D-2D structure to enhance its visible light absorption. Optical and morphological study presents successful incorporation of ZC-LDH on the surface of GCN-ns. Through adjusting of GCN-ns by ZC-LDH lower recombination rate of e−/h+ pairs, longer lifetimes and an increase in contamination reduction was brought out. The binary nanocomposite was employed to effectively degrade Rhodamine B under UV/vis light irradiation. The improvement in photocatalytic abilities was proven to be related to in situ self-production of H2O2 on GCN-ns/ZC-LDH surface by Xe light irradiation which in return accounts for additional hydroxide radical generation. Radical quenching experiments specified the main active species involved while the consequent step-scheme (S-scheme) charge transfer mechanism was proposed.

Successive cytotoxicity control by evolutionary surface decorated electronic push-pull green ZnCr-LDH nanostructures: Drug delivery enlargement for targeted breast cancer chemotherapy

The reason for the increasing bioavailability and biocompatibility of the porous nanomaterials in the presence of different (bio)molecules is still unknown. The role of difference functional groups and their interactions with the potential bioavailability and biocompatibility is of great importance. To investigate the potential contribution of the electronic effects (especially on the surface of the porous nanomaterials) on their biomedical behavior, a series of surface-decorated green ZnCr-layered double hydroxide (LDH) porous nanocarriers is developed as a non-viral vector. Different conjugations investigated these porous LDHs for optimizing and minimizing the cytotoxicity for targeted breast cancer therapy. Quick low-temperature synthesized ZnCr-LDH nanocarriers method with enlarged drug delivery windows decorated with leaf extracts and benzamide-like molecules revealed a push-pull electronic synergistic effect on cytotoxicity and enhanced cell viability, biocompatibility, aggregations, and interactions with the cell membranes. The pre-defined model drug, doxorubicin (DOX), unraveled chemotherapy performance in response to MCF-7 cell lines, with ≈ 60% drug payload contributed from functional groups of leaf extracts. Moreover, electron-poor and electron-rich benzamide-like molecules attached to the ZnCr-LDH surface enhanced the relative cell viability up to 29% and 32%, respectively. The in vivo experiments on breast cancer of treated mice (H&E) revealed unaggregated cellular arrays and antibacterial activity against E. coli (gram-negative) and S. aureus (gram-positive) bacteria. Benzamide-like ZnCr-LDH nanocarriers showed a suitable zone of inhibition beyond 10 mm, compared to the standard. Cytotoxicity control achieved herein seems promising for the future ahead of nanomedicine.

Simultaneous in Situ Exfoliation of Titanate and Zn–Cr Layered Double Hydroxides with a Copolymer for Photocatalytic Degradation of Organic Pollutants

Simultaneous <i>in Situ</i> Exfoliation of Titanate and Zn–Cr Layered Double Hydroxides with a Copolymer for Photocatalytic Degradation of Organic Pollutants

Fabrication of a coated BiVO4@LDHs Z-scheme heterojunction and photocatalytic degradation of norfloxacin

The decahedral morphology of BiVO4 and ZnCr-layered double hydroxides (LDHs) nanosheets enables the construction of a BiVO4@LDHs Z-scheme heterojunction (BiVO4 as core and LDHs as a shell) for photocatalytic degradation of norfloxacin, typical antibiotic. The effects of initial concentration of norfloxacin, catalyst loading, reaction temperature, and pH value on the performance of photodegradation were studied. It was found that the removal of norfloxacin can reach 90.3% under the optimized conditions. The core-shell structure enhances the specific surface area, improves the energetic alignment of the band structures, and produces enough hydroxyl and superoxide radicals to degrade norfloxacin. Density functional theory (DFT) calculations show that a built-in electric field is formed between ZnCr-LDHs and BiVO4, which promotes the transfer of photogenerated electrons from the valence band of ZnCr–LDHs to the conduction band of BiVO4. This transfer accelerates the flow of photogenerated electrons and reduces the recombination of electron-hole pairs, so that BiVO4@LDHs heterojunction shows excellent photocatalytic activity for norfloxacin.

Zinc-chromium layered double hydroxides anchored on carbon nanotube and biochar for ultrasound-assisted photocatalysis of rifampicin

In this study, ZnCr layered double hydroxide (LDH), ZnCr LDH/carbon nanotube (CNT), and ZnCr LDH/Biochar (BC) were synthesized and characterized by various analyses. The successful synthesis and the great crystallinity of the samples were consented by XRD analysis. SEM and TEM were applied to study the morphology of the synthesized samples. The simultaneous presence of C, Zn, and Cr elements was well confirmed by EDX and dot mapping analyses demonstrating the successful preparation of nanocomposites. According to the BET analysis, ZnCr LDH nanocomposites with BC and CNT had more specific surface area compared to ZnCr LDH alone. The catalytic performances of the samples were determined for the degradation of rifampicin (RF). The degradation efficiency of the sonophotocatalytic process in the presence of 0.6 g L−1 of ZnCr LDH/BC toward 15 mg L−1 of RF under 150 W ultrasound and visible light irradiation was found to be about 100% within 40 min. The influence of the reactive species on the sonophotocatalytic process was assessed via the addition of different scavengers (para-benzoquinone (p-BQ), formic acid (FA), isopropyl alcohol (IPA)), and enhancers (hydrogen peroxide and potassium persulfate). The GC–MS analysis was carried out and eleven by-products during the RF decomposition were detected.

Synthesis, Characterization and Photocatalytic Performance of Calcined ZnCr-Layered Double Hydroxides.

The development of new materials for performing photocatalytic processes to remove contaminants is an interesting and important research line due to the ever-increasing number of contaminants on our planet. In this sense, we developed a layered double hydroxide material based on Zn and Cr, which was transformed into the corresponding oxide by heat treatment at 500 °C. Both materials were widely characterized for their elemental composition, and structural, morphological, optical and textural properties using several experimental techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, UV-vis spectroscopy and physisorption techniques. In addition, the photocatalytic activity of both materials was analysed. The calcined one showed interesting photocatalytic activity in photodegradation tests using crystal violet dye. The operational parameters for the photocatalytic process using the calcined material were optimised, considering the pH, the initial concentration of the dye, the catalyst load, and the regeneration of the catalyst. The catalyst showed good photocatalytic activity, reaching a degradation of 100% in the optimised conditions and showing good performance after five photodegradation cycles.

Facile layer-by-layer self-assembly of 2D perovskite niobate and layered double hydroxide nanosheets for enhanced photocatalytic oxygen generation

Photocatalytic O2-generation reaction is recognized as a crucial step in water splitting and has drawn great attention of researchers. In this work, a hetero-layered composite photocatalyst was successfully prepared by a facile self-assembly method based on electrostatic interaction between oppositely charged Zn/Cr-layered double hydroxide (Zn/Cr-LDH) and lead niobate nanosheets. The layer-by-layer stacking of Zn/Cr-LDH and HPb2Nb3O10 nanosheets was beneficial for rapid migration of photo-induced charge carriers inside the photocatalyst because of large contact area. In the meantime, Zn/Cr-LDH and HPb2Nb3O10 components exhibited suitable energy-band alignment, which led to efficient separation of photo-induced charge carriers. The composite photocatalyst showed enhanced photocatalytic O2-generation activity under visible-light irradiation without loading cocatalyst. Briefly, this work expanded the applications of AB2Nb3O10-based materials in photocatalytic energy conversion and proved that constructing composites based on electrostatic self-assembly of complementary 2D materials is a promising strategy for development of more efficient photocatalysts.

A Comparative Study on The Adsorption Behavior of Congo Red on to ZnAl and ZnCr Layered Double Hydroxides

In this work, two synthetic layered double hydroxides (LDH) consists of Zn2+ as M2+ cation with different M3+ cation, i.e., Al3+ and Cr3+ were used as an adsorbent for Congo Red removal aqueous solution. Both Zn-Al and Zn-Cr LDH were characterized by X-ray diffraction, FT-IR, and BET surface area analyzer. The effect of contact time, initial dye concentration, and temperature were evaluated in a batch technique in order to investigate the characteristic of Congo Red adsorption onto both adsorbents. The experimental data were assessed according to the parameter of adsorption kinetics, isotherm, and thermodynamics. The results of LDH characterization showed that Zn-Al LDH has a higher interlayer distance than Zn-Cr LDH, although Zn-Cr LDH has a higher surface area. The FT-IR analysis indicated the interlayer space of both Zn-Cr and Zn-Al LDH was dominated by CO32- as the interlayer anion species. The adsorption kinetics study of Congo Red on both LDH revealed that the adsorption process followed the pseudo-second-order model. For the adsorption isotherm, the experimental data fit well with the Freundlich model rather than the Langmuir model. The thermodynamic study indicated that the adsorption process that occurred on both adsorbents was spontaneous with exothermic nature.

An amine functionalized ZnCr LDH/MCM-41 nanocomposite as efficient visible light induced photocatalyst for Cr(VI) reduction

Achieving photocatalytic carcinogenic hexavalent chromium (Cr(VI)) reduction by utilising a visible light promoted semiconductor based nanocomposite is challenging as a eco-friendly and sustainable approach. Mesoporous MCM-41 modified ZnCr Layered double hydroxide (LDH) nanocomposite was prepared by in-situ co precipitation method having great porosity, large surface area, high chemical stability and plentiful surface –OH grafting sites. These sites can be easily tailored with APTES group as amine source using a facile reflux process to design amine functionlisation ZnCr LDH/MCM-41 nanohybrid material. The structural identity, textural properties, optical response and functional groups of the as-prepared materials were systematically analysed by powder X-ray diffraction (PXRD), N2 adsorption–desorption technique, ultraviolet–visible diffuse reflectance (UV–vis DRS) and fourier-transform infrared (FTIR). It is revealed that the amine functionlisation ZnCr LDH/MCM-41 possesses enhanced visible-light absorption property in compared to ZnCr/MCM-41 nanocomposite, which was attributed to the chromophoric amino group of the organic linker. Under optimum conditions, amine functionlisation ZnCr LDH/MCM-41 exhibited 95% Cr(VI) reduction in 2 h from aqueous solution under visible-light irradiation, which was 1.2 times higher than that of unmodified ZnCr LDH/MCM-41 nanocomposite and 1.5 times superior than pure ZnCr LDH. The lowest PL intensity of amine functionlisation ZnCr LDH/MCM-41 supported the optimum photocatalytic activity. Under the explore of visible light, the presence of LMCT spectra (O2p → Cr-3dt2g and Zn 4 s) an d–d transition (Cr-3d-t2g → Cr-3 deg) in the ZnCr LDH are the key reason for excited of photoelectrons and transportation from amine functionlisation ZnCr LDH/MCM-41 to Cr(VI), accelerating the reduction process of Cr(VI). In summary, amine functionalized MCM-41 modified ZnCr LDH could be prospective photocatalyst candidate for the treatment of Cr(VI)-contained wastewater under visible light irradiation.

花状锌铬层状双金属氢氧化物的制备及其光催化性能的研究

花状锌铬层状双金属氢氧化物的制备及其光催化性能的研究

Layered double hydroxides@poly(p-phenylenediamine)@Cu as a novel catalyst for the synthesis of pyrrole derivatives: preparation and characterization

In this research, the synthesis route of ZnCr-layered double hydroxides functionalized with poly(p-phenylenediamine) and Cu(II) was described. LDHs@PpPDA@Cu was synthesized as a novel, green, and recyclable catalyst and characterized by various techniques including Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry analysis, X-ray diffraction, and energy dispersive X-ray analysis. The catalytic activity of the LDHs@PpPDA@Cu was investigated in the synthesis of pyrrole derivatives via one-pot four-component coupling of amine, aldehyde, nitromethane and acetylacetone. The results of analyses demonstrated that the reactions proceeded to completion which has led to the successful synthesis of high purity compounds.

Construction of a Z-Scheme Dictated WO3-X /Ag/ZnCr LDH Synergistically Visible Light-Induced Photocatalyst towards Tetracycline Degradation and H2 Evolution.

Herein, we have designed nonstoichiometric WO3, coupled with ZnCr layered double hydroxide (LDH) nanosheeet through Ag nanoparticle as the solid-state electron mediator to form WO3–X/Ag/ZnCr LDH Z-scheme photocatalyst. The presence of oxygen defect levels in as-synthesized materials was confirmed by Raman, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) analyses. The photocatalytic performance of the catalysts was investigated by the tetracycline degradation and H2 energy production under visible light irradiation. The WO3–X/Ag/ZnCr LDH ternary heterostructure exhibits superior activity toward tetracycline degradation and hydrogen evolution. The excellent photocatalytic performance of the catalyst was attributed to the synergistic effects among three species (WO3–X, Ag, and ZnCr LDH) and the enhanced separation efficiency of photoinduced charge carriers through the Z-scheme WO3–X/Ag/ZnCr LDH system. In addition, the created oxygen deficiency on WO3–X could improve the photocatalytic behavior of ZnCr LDH in heterostructure by delaying the recombination efficiency of photoexcited electron–hole pairs. Furthermore, the higher affinity of tetracycline at the oxygen defect levels of the photocatalyst supports the high rate of tetracycline degradation. The enhanced photocatlytic activity of the catalysts was further supported by PL spectra and photoelectrochemical studies (electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) plot). The present research opens up a new strategy for designing highly efficient visible light-induced Z-scheme-based photocatalysts with high population of active sites for energy and environmental applications in a sustainable manner.

Enhanced photocatalytic performance of a Ti-based metal-organic framework for hydrogen production: Hybridization with ZnCr-LDH nanosheets

Novel hybrid composites of NH2-MIL-125(Ti) and ZnCr-layered double hydroxide nanosheets (ZnCr-LDH NSs) are developed for use as visible-light-active photocatalysts for hydrogen production based on water photolysis. The hybrid composites are obtained by growing NH2-MIL-125(Ti) in the presence of exfoliated ZnCr-LDH NSs using a solvothermal reaction. Hybridization of NH2-MIL-125(Ti) with exfoliated ZnCr-LDH NSs leads to significant effects on the morphology and optical properties of NH2-MIL-125(Ti). To find the optimum photocatalytic activity for hydrogen production by the hybrid composite photocatalysts, the content of ZnCr-LDH in this work is controlled. Compared to that of pristine NH2-MIL-125(Ti) and ZnCr-LDH, the hybrid composites exhibit an improved photocatalytic activity for hydrogen production under visible-light irradiation. In addition, the hybrid composite photocatalyst shows excellent photo-chemical stability. The improved photocatalytic activity is believed to benefit from the synergy of strong electronic coupling between NH2-MIL-125(Ti) and ZnCr-LDH NSs, expanded light absorption and band alignment to enhance the lifetime of photo-induced electrons and holes.

A plasmonic AuPd bimetallic nanoalloy decorated over a GO/LDH hybrid nanocomposite via a green synthesis route for robust Suzuki coupling reactions: a paradigm shift towards a sustainable future

A plasmonic AuPd bimetal-decorated GO/LDH nano-photocatalyst displays encouraging Suzuki coupling performance under visible light illumination.