ZnO Catalyst Research Articles

Stephania abyssinica leaf extract mediated (Mn, Ni) co-doped ZnO catalyst synthesis for the degradation of organic dye

In this work, the (Mn, Ni) co-doped ZnO catalyst was prepared using Stephania abyssinica leaf extract. The prepared sample was assigned with Zn0.98-xMn0.02NixO (x = 0.01, 0.03, 0.05, 0.07, 0.09) and abbreviated as 1NMZO, 3NMZO, 5NMZO, 7NMZO, and 9NMZO, respectively. For comparison purposes, the pure ZnO, Mn-doped ZnO (2 % Mn) (2MZO), and Ni-doped ZnO (5 % Ni) (5NZO) were also prepared with the same procedure mentioned above. The catalysts were characterized by using different instruments. The photocatalytic activities of the catalysts were also evaluated for the degradation of Methylene Blue (MB) dye under visible light. It is showed that pure-ZnO, 2MZO, 5NZO, 1NMZO, 3NMZO, 7NMZO, and 9NMZO catalysts had 33.12, 76.63, 79.73, 84.51, 92.81, 97.34, and 92.30 % degradation efficiency, respectively. However, 5NMZO catalyst showed the highest photocatalytic activity and degrades 99.53 % of MB dye. The higher degradation efficiency of the 5NMZO catalyst could be due to the lower recombination rates of the photo-generated electrons and holes; lower electron transfer resistance; the higher surface area; and higher absorption capacity of the catalyst under visible light. Therefore, (Mn, Ni) co-doped ZnO prepared with Stephania abyssinica leaf extract could be the best candidate for the degradation of organic pollutants.

Turning abundant waste sulfur to polymers for manufacturing: Exploiting role of organic crosslinkers and benign catalysts

Abundant source of sulfur produced as byproduct of refineries demands sustainable valorization solutions. Use of organic crosslinkers and benign catalysts to polymerize sulfur for use in manufacturing offers a sustainable value-added application. This paper introduces MgO as an effective benign catalyst and oleic acid as an organic crosslinker for inverse vulcanization of sulfur. We further compare efficacy of MgO with other metal catalysts (ZnO and CaO) using molecular modeling and laboratory experiments. ZnO is commonly used in elastomeric formulations; however, industries try hard to keep the ZnO level low because of its environmental impact, particularly on aquatic organisms, and for economic reasons. Our rheological characterization shows the inverse vulcanization is enhanced when MgO is present as evidenced by the increase of viscosity of sulfur-oleic acid blends by 94 % relative to the blend without catalyst and 39 % relative to the blend with ZnO catalyst. Based on our quantum-based molecular modeling, using density functional theory (DFT), coordination complexes of Mg oleate (Mg (RCOO)2), made from the reaction between oleic acid and MgO, are energetically better stabilized compared to Zn or Ca oleate. Stronger interactions in Mg oleate, leading to the more stabilized coordination complexes, could be a reason for higher viscosity for MgO/sulfur-oleic acid compared to ZnO/sulfur-oleic acid. In complexes of sulfur and metal oleate, regardless of the electronic nature of sulfur chains (ionic or radical form), coordination complexes containing MgO show binding energies that are higher than those of Zn complexes and notably higher than those of Ca complexes, indicating capability of Mg substitution in Zn oleate compounds as catalysts. Studying the addition reactions of sulfur radicals to oleic acid and the formation of CS bonds, using DFT modeling, shows the superiority of allylic (CHCHĊH) sites of oleic acid over olefinic (CC) sites in reactions of sulfur radicals. Compared to sulfur radicals, sulfur chains in ionic character provide higher binding energies with metal oleates because of the electrostatic interactions between the positively charged metal and negative sulfur atoms. The study outcomes support sustainability and resource conservation in chemical manufacturing and petroleum refining industry.

Green Synthesis and Characterization of LED-Irradiation-Responsive Nano ZnO Catalyst and Photocatalytic Mineralization of Malachite Green Dye

The green synthesis of nanoparticles is an emerging branch of nanotechnology in recent times, as it has numerous advantages such as sustainability, cost-effectiveness, biocompatibility, and eco-friendliness. In the present research work, the authors synthesized ZnO nanoparticles (ZnO NPs) by a green and eco-friendly method. The synthesized ZnO NPs were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR) spectroscopic techniques. The calculated average crystallite size of ZnO NPs was observed at 36.73 nm and FESEM images clearly showed the cylindrical shape of nanoparticles. The absorption peak at 531 cm−1 was observed in the FTIR spectrum of the ZnO NPs sample, which also supports the formation of the ZnO wurtzite structure. Finally, the synthesized ZnO NPs potential was analyzed for the remediation of malachite green from an aqueous solution. The ZnO NPs showed a desirable photocatalytic nature under LEDs irradiation.

An Approach for Modeling, Simulation, and Optimization of Catalytic Production of Methyl Ethyl Ketone

The current exploration manifests the progress of a one-dimensional reactor for the production of methyl ethyl ketone (MEK) as a commercial-industrial solvent with a relatively rapid evaporation rate and high solvation ability. MEK has been extensively utilized in colorings, printing, artificial leather, and base oils. One of the methods for the production of MEK is catalytic dehydrogenation of 2-butyl alcohol in the temperature range of 650–750 K utilizing spherical ZnO catalyst. Considering the high cost of fossil fuels to achieve optimal energy consumption, thermal coupling with the Fischer–Tropsch reaction was employed. Eventually, an evolutionary genetic algorithm was adopted to optimize the reactor to maximize MEK production. MATLAB software was utilized for the modeling and optimization. The modeling results were verified by industrial data. Moreover, they indicated a 37 and 55.4% increase in the production rate of thermal coupling and optimal thermal coupling reactors, respectively.

Enhanced Photocatalytic Activity and Charge Carrier Separation of a Nickel Impregnated Zinc Oxide Catalyst for the Visible Photodegradation of Remazol Brilliant Violet-5R and Methyl Orange

ZnO was impregnated with Ni in order to increase its photocatalytic performance in the visible region. The Ni-impregnated ZnO catalyst was synthesized by wet impregnation. The synthesis of Ni/ZnO catalyst, its morphological analysis and elemental analysis was confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy which confirmed that 4.66% Ni was impregnated at the surface of ZnO. The synthesized catalyst was applied for the photocatalytic degradation of Remazol Brilliant Violet-5R (RBV-5R) and methyl orange (MO) in aqueous solution. The catalyst dosage, pH, dye concentration, and effect of scavengers were optimized. 98.92% degradation of RBV-5R was observed at pH 10 using 0.1 g of catalyst, 5 mmol H2O2 in 20 min, whereas 83.77% MO was degraded using 0.2 g of the catalyst at pH 4 in 30 min. The order of reaction was also determined by applying kinetic models and the degradation followed pseudo first-order kinetics for both dyes.

Sono-photocatalytic activity of sea sediment@400/ZnO catalyst to remove cationic dyes from wastewater

A photocatalyst was generated from sea sediments and ZnO and tested in the sono-photocatalytic removal of methylene blue (MB) and crystal violet (CV).. The results of FTIR, XPS, and XRD analyzes showed that there are different functional groups in the photocatalyst and also the photocatalyst has a crystalline structure. The BET surface area for sea sediment, sea sediment @400 °C, ZnO, and sea sediment @400 °C/ZnO was determined to be 1.787, 4.326, 24.057, and 9.212 m2.g−1, respectively. The maximum removal efficiency of MB (97.85%) and CV (99.14%) has happened at pH 8, contact time of 40 min, hydrogen peroxide dose of 50 µL/100 mL, catalyst dose of 1 g.L−1, and dye content of 10 mg.L−1 under ultrasonic process (180 W, 24 kHz). The effect of scavengers was investigated to determine the type of radicals effective in the removal process. The results showed that the •OH, •O2–, and electron radicals had an effective role in the dye removal process. The pseudo-first-order kinetic model had a good ability to describe data and the reaction rate constant for removing CV and MB dyes was determined to be 0.0671 and 0.052 min−1, respectively. The treatment of industrial wastewater was successfully done by the prepared photocatalyst. The treated aqueous solution had no toxicity for microorganisms, germination, and plant growth. Thus, the resulting water from the process can be used successfully for agricultural purposes.

Dual‐Scale Integration Design of Sn–ZnO Catalyst toward Efficient and Stable CO2 Electroreduction (Adv. Mater. 38/2022)

Dual‐Scale Integration Design of Sn–ZnO Catalyst toward Efficient and Stable CO₂ Electroreduction (Adv. Mater. 38/2022)

Degradation of Methyl Green Dyes with ZnO Catalyst using the Photosonolysis Method

Textile and dyestuff industrial dye waste remain the most difficult wastewater to treat due to the complex aromatic molecular structure of industrial dyes, which are very difficult to decompose. This research was conducted on the degradation of methyl green using the photosonolysis method. The purpose of this study was to determine the optimum time and amount of ZnO used in degrading methyl green dye. The results of the percentage degradation were obtained from the absorbance value measured using a UV-Vis Spectrophotometer. (λmax) Methyl green obtained from the measurement of a UV-Vis spectrophotometer was 640 nm. The results showed that the optimum irradiation and sonication time to degrade methyl green was 60 minutes with a degradation percentage of 92.77%. For the effect of mass variation of ZnO catalyst obtained the optimum mass of 0.05 grams with a degradation percentage of 96.38%.

Dual-Scale Integration Design of Sn-ZnO Catalyst toward Efficient and Stable CO2 Electroreduction.

Electrochemical CO2 reduction to CO is a potential sustainable strategy for alleviating CO2 emission and producing valuable fuels. In the quest to resolve its current problems of low-energy efficiency and insufficient durability, a dual-scale design strategy is proposed by implanting a non-noble active Sn-ZnO heterointerface inside the nanopores of high-surface-area carbon nanospheres (Sn-ZnO@HC). The metal d-bandwidth tuning of Sn and ZnO alters the extent of substrate-molecule orbital mixing, facilitating the breaking of the *COOH intermediate and the yield of CO. Furthermore, the confinement effect of tailored nanopores results in a beneficial pH distribution in the local environment around the Sn-ZnO nanoparticles and protects them against leaching and aggregating. Through integrating electronic and nanopore-scale control, Sn-ZnO@HC achieves a quite low potential of -0.53V vs reversible hydrogen electrode (RHE) with 91% Faradaic efficiency for CO and an ultralong stability of 240 h. This work provides proof of concept for the multiscale design of electrocatalysts.

Photocatalytic efficiency of undoped and Cu-doped ZnO thin films coated inside transparent glass tube as one-piece photoreactor

In recent years, the contaminated rejects due to the rise of textile and dye industry have dramatically affected the ecosystem and aquatic reserves. In addition, the decontamination of organic species based on nanoparticles as photocatalyst is considered as a complicated route and material consumer. To address the separation issue, it is necessary to develop new methods to degrade organic dyes through coast effective processes. In this context, we present in our study a new photocatalysis design by implementation of the photocatalyst on the inner side surface of transparent glass tube as one piece-photoreactor. Among various Photocatalysis based on metal-oxide materials, zinc oxide is widely studied by tailoring its physical and chemical properties to improve the photocatalytic degradation activity. Accordingly, pure and Cu-doped ZnO catalysts with variable copper amount (1, 2.5 and 4 wt%) were synthesized by ultrasonic spray pyrolysis and characterized by X-ray diffraction (XRD), Raman spectroscopy, UV–visible spectroscopy, Photoluminescence spectroscopy (RT-PL), Atomic force microscopy (AFM), Scanning electron microscopy (SEM), Complex impedance spectroscopy and X-ray photoelectron spectroscopy (XPS). The methylene blue degradation rate was investigated through the decrease of the absorption band situated at 663 nm under UV–Vis irradiation. The reusability of the undoped and Cu-doped ZnO photocatalyst tests after six recycles give a steady photodegradation efficiency results.

Synthesis of Sn-doped ZnO catalysts by solution combustion method for photocatalytic activity: a parametric study

Synthesis of Sn-doped ZnO catalysts by solution combustion method for photocatalytic activity: a parametric study

Experimental and Modelling Comparison of the Effects of UV Energy on Liquefaction Efficiency in Coal Liquefaction Mechanism

Coal liquefaction process gives very efficient results, especially for value-added chemicals production from low-quality coal. However, when the literature is examined, notably there is not enough scientific study for liquefaction mechanisms. Here, in this study, There are five different liquefaction mechanisms of Beypazarı coals. It includes four different UV light power and a catalyst environment using 180 watts of UV power. Created first-order linear discrete models were proposed and compared with the experimental results. Additionally, the reaction rate constants for each proposed kinetic model were calculated using the Kalman filter method. However, to evaluate the compatibility of the experimental results and the modeling results, the sum of the squared differences of the values calculated from the experimental data and the models was examined. Because of these studies, it has been observed that the rate constants of direct oil formation from coal at 120 and 180 watts of UV power are at least three times greater than the rate constants for the formation of asphaltene and pre-asphaltene from coal. Simultaneously, The results demonstrate that models with reversible and parallel steps are more compatible with experimental data. Experimental data and modeling results are much more compatible with the studies conducted on Beypazarı coals in a 180-watt UV-catalyzed environment compared to a 180-watt catalyst-free environment. In the presence of ZnO catalyst, the rate constants occurring in the conversion reaction from coal to oil were again three times faster than the conversion rate constants from coal to asphaltene and from coal to preasphaltene. In the modeling and experimental results conducted in the catalyst environment, the efficiency was higher than the catalyst-free environment. The best fit was obtained using model that has both reversible (between asphaltene: coal, asphaltene: oil, and asphaltene: preasphaltene) and irreversible (coal: oil, coal: preasphaltene and preasphaltene: oil) reaction steps. The model also evidenced that reversible reactions are critical on the liquefaction of Beypazarı coal.

Preparation and Characterization of Polylactic Acid by Ring Opening Polymerization Using Unconventional Heating System

Polylactic acid (PLA) has been synthesized via ring opening polymerization (ROP) for the Lactide cyclic dimmer under microwave irradiation with a constant power of 300W using ZnO catalyst. The structural formula of PLA was established using spectroscopic techniques FTIR, 1HNMR, and 13CNMR. The thermal properties were investigated using DSC and TGA techniques. The DSC thermogram exhibited two endothermic transitions at (115-132) C° which related to the melting of the polymer, while the TGA thermogram showed one main decomposition step at 265°C. The viscosity average molecular weight [] of the obtained polymer was (7.8×103 gm/mol). The SEM morphology study exhibited homogenous and dense surface with no separate entities

Cellulose template designed porous ZnO based catalysts with different valence copper for solar photocatalytic CO2 conversion

Designing a green method to enhance the utilization of photocatalysts on solar energy was of great significance to alleviate energy problems. The porous ZnO-based catalysts with different valence copper (CuO−ZnOCel-T and Cu−ZnOCel-T) were successfully obtained by using cellulose fibers as templates, which possessed three-dimensional structures and excellent photocatalytic activities. The dispersibility of CuO−ZnOCel-T nanoparticle was influenced by surface groups of cellulose template, the more active sites of composite catalyst were exposed than CuO−ZnO catalysts with carbon fiber as the template and CuO−ZnO powders without any template. Moreover, to explore the effects of different valence states of Cu on the photocatalytic activity of ZnO nanoparticles, wheat straw was used to reduce CuO−ZnOCel-T to Cu−ZnOCel-T by using pyrolysis reduction treatment of wheat straw. The CO production rate of Cu−ZnOCel-T (30.17 µmol*g−1h−1) was significantly higher than CuO−ZnOCel-T (8.61 µmol*g−1h−1) based on the same catalyst morphologies, indicating that the surface plasmon resonance (SPR) effect of Cu was more favorable for improving catalytic activities of ZnO than the structure effect of CuO−ZnOCel-T heterojunction. This work proposed an exciting idea for using biomass materials to tailor the photocatalytic performance of catalysts and reduce copper ions in a cleaner method.

Catalytic Decomposition of Azo Dye Using ZnO in Sunlight

The degradation of azo is a challenge for environmentalists. Catalytic decomposition of azo dyes by ZnO heterogeneous photocatalysis and the influence of operating parameters such as light intensity, temperature, amount of ZnO catalyst, solution pH and amount of pollutants. It has been observed that ZnO catalysts is quite capable of removing azo dyes in the presence of sunlight. We can use the same catalyst over and over, and it works well every time. We recovered 99% clear water within a few hours of exposure to sunlight.

“Fe3+ modified zinc oxide nanomaterial as an efficient, multifaceted material for photocatalytic degradation of MB dye and ethanol gas sensor as part of environmental rectification”

• Fabrication of undoped ZnO and 5% Fe/ZnO by co-precipitation method. • Efficient removal of MB dyes under UV light irradiation. • Comparative study of prepared catalysts for water purification techniques. • Ethanol gas sensing application of modified ZnO material. • Humidity sensing study for the modified ZnO catalyst. In the present investigation, we report the preparation of 5% Fe 3+ doped zinc oxide (5% Fe/ZnO) nanocatalyst for organic transformations, gas sensing, and organic pollutant elimination applications via the CPT method. A broad range of analytical techniques was applied to attribute the successful modification of the nanocatalyst and to evaluate the structural and morphological properties, surface area, and chemical compositions by the x-ray diffraction, scanning electron microscopy, high resolution-transmission electron microscopy, Brunauer-Emmett-Teller, and energy dispersive spectroscopy techniques. The photocatalytic degradation of methylene blue (MB) as organic pollutant and gas sensing performance to ethanol were studied thoroughly. Due to enhanced gas sensing performance comparatively at low temperature to ethanol, it is known for ideal sensor, which has high selectivity, rapid response-recovery time, and high stability. It also showed the enhanced photocatalytic performance in the degradation of MB dye in the aqueous heterogeneous suspension. The efficiency of the semiconductor photocatalyst is found higher at the small amount of catalyst dose (0.8 g/L) and at the contact time of 100 min and pH 8.0 as operating parameters. Further, the organic transformation mechanism, enhanced gas sensing and, photodegradation mechanism were explained as the synergic effect of the ZnO and Fe doping. The results revealed that 5% Fe/ZnO nanocatalyst is promising approach to aim the goal of achieving a superior heterogeneous catalyst for the elimination of organic pollutant (MB) at optimum conditions and gas sensing performance for the detection of ethanol.

Fabrication of FeO3 sites in FeOx/ZnO for efficient and selective photo-catalytic oxidation of methane to liquid oxygenates

New catalysts and product diversification of direct CH 4 conversion remain very challenging in catalysis. Here, we report FeO x /ZnO photo-catalysts for the conversion of CH 4 to liquid oxygenates with high yield (4,108 μmol·g cat −1 ·h −1 ) and nearly 100% selectivity. Based on the combinative results from X-ray photoelectron spectroscopy, X-ray absorption, electron paramagnetic resonance, radical quenching, and theoretical calculations, it is found that, in addition to the activation of CH 4 in the liquid phase, the presence of highly dispersed FeO 3 motifs in the ZnO lattice facilitates the formation of surface-active O − species; this plays an effective role for CH 4 activation to · CH 3 radicals. Meanwhile, HCHO is obtained as the major product in our system, rather than the typically reported CH 3 OH, and this may offer new opportunities to extend the product structure of CH 4 upgrading via tandem catalysis. • FeO x /ZnO catalysts show excellent efficiency in photo-catalytic oxidation of CH 4 • HCHO, rather than CH 3 OH, is obtained as the main product • A pyramidal FeO 3 structure is essential for the high performance Methane activation and conversion are important topics in catalysis. Hao et al. present FeO x /ZnO photo-catalysts for the conversion of CH 4 to liquid oxygenates with excellent yield and selectivity, which may offer new opportunities for CH 4 upgrading via tandem catalysis.

Boosting CO2 hydrogenation to methanol via Cu-Zn synergy over highly dispersed Cu,Zn-codoped ZrO2 catalysts

Supported Cu nanoparticle catalysts are the main players in hydrogenation of CO2 to methanol, however, the challenges in selectivity and catalyst stability have not been properly addressed due to the reverse water-gas shift reaction initiated by Cu nanoparticles and their sintering/oxidation. Here, we have developed a series of Cu,Zn-codoped ZrO2 catalyst, in which Cu and Zn are highly dispersed into the matrix of ZrO2. The optimal Cu,Zn-codoped ZrO2 catalyst demonstrates outstanding performance compared with Cu-doped ZrO2, Zn-doped ZrO2 and Cu-doped ZnO catalysts. Chemisorption, H2-D2 exchange and in situ diffuse reflectance infrared Fourier transform spectroscopy analyses reveal that the synergy interaction between the doped Zn and Cu plays a crucial role in boosting the selective production of methanol synthesis via promoting CO2 adsorption and H2 dissociation. This study provides an intriguing example for the development of selective and stable Cu-catalyst for the CO2 hydrogenation via metal-doping strategy.

Photocatalytic Degradation of Recalcitrant Pollutants of Greywater

These days, many countries have a water shortage and have limited access to clean water. To overcome this, a new treatment is emerging, namely, the photocatalytic processing of greywater. Photocatalytic processes to remove the organic matter from different greywater sources are critically reviewed. Their efficiency in degrading the organic matter in greywater is scrutinized along with factors that can affect the activity of photocatalysts. Modified TiO2, ZnO and TiO2 catalysts show great potential in degrading organic materials that are present in greywater. There are several methods that can be used to modify TiO2 by using sol-gel, microwave and ultrasonication. Overall, the photocatalytic approach alone is not efficient in mineralizing the organic compounds, but it works well when the photocatalysis is combined with oxidants and Fe3+. However, factors such as pH, concentration and catalyst-loading of organic compounds can significantly affect photocatalytic efficiency.

Morphology-controllable ZnO catalysts enriched with oxygen-vacancies for boosting CO2 electroreduction to CO

Electrochemical CO2 reduction (ECR) is a promising approach to realize carbon neutral and energy sustainability, which is still impeded by the low selectivity and activity for application. Defect engineering of electrocatalysts, especially oxygen vacancy introduction into metal oxide materials has been proved to be an effective strategy to satisfy thermodynamic condition and improve kinetics for ECR. Herein, we synthesize oxygen vacancy-enriched ZnO nanoparticle catalysts for efficient ECR through electrospinning technique using particular precursor. Characterizations reveal that the utilization of Zn(CH3COO)2 precursor contributes to the generation of oxygen vacancies in ZnO catalysts which enhances CO2 adsorption and stabilizes the intermediate. In a flow cell configuration, a current density of 150 mA cm−2 and a CO Faradic efficiency > 80% can be obtained for ZnO nanoparticle catalysts (p-ZnO-800), which is meaningful for industry.