ZnO Catalyst Research Articles

Modification research on the hydrogen storage performance of bimetallic oxide Zn2Ti3O8 on MgH2

In this study, flake Zn2Ti3O8, TiO2 and rod ZnO catalysts were successfully synthesized by hydrothermal and calcination methods, and the catalytic performance of the three catalysts for MgH2 was compared. Notably, Zn2Ti3O8 had a significant synergistic enhancement effect on the dehydrogenation temperature and desorption kinetics of MgH2. The experimental results showed that the dehydrogenation of MgH2 + 12 wt% Zn2Ti3O8 composite started at about 195 °C, which was about 150 °C lower than that of pure MgH2. Moreover, at 325 °C, MgH2 released only 3.06 wt% H2 in 20 min, whereas the MgH2 + 12 wt% Zn2Ti3O8 composite released the same amount of hydrogen at 250 °C in 3 min. After complete dehydrogenation, the MgH2 + 12 wt% Zn2Ti3O8 composite initiated hydrogen uptake at 40 °C and absorbed about 6.05 wt% of H2 in 60 min at 200 °C. The hydrogen uptake activation energy and dehydrogenation activation energy of the composites were reduced by 24.56 kJ/mol and 44.67 kJ/mol, respectively, when compared to the pure MgH2. Cycling experiments showed that after 20 cycles, the MgH2 + 12 wt% Zn2Ti3O8 composite maintained good cycling stability and the hydrogen storage capacity was still more than 96 %. Therefore, the composite exhibits excellent catalytic and hydrogen storage properties, and has potential applications in improving the hydrogen release rate and reducing the activation energy.

Titanosilicate-1 Supported ZnO Catalysts for Steady Propane Dehydrogenation Performance

Titanosilicate-1 Supported ZnO Catalysts for Steady Propane Dehydrogenation Performance

Liquid-phase hydrogenation of dimethyl maleate to 1,4-butanediol over a sorbitol-modified Cu@C/ZnO catalyst

Liquid-phase hydrogenation of dimethyl maleate to 1,4-butanediol over a sorbitol-modified Cu@C/ZnO catalyst

Construction of frustrated lewis pairs in ZnO surface for boosting electrocatalytic NO reduction to NH3: Theoretical prediction and experimental validation

Herein, we reported the design of unique FLPs for electrocatalytic reduction of nitric oxide (NOER) through anion doping on the ZnO (100) surface. The results demonstrated that the introduced dopant and its adjacent non−bonding Zn site function as a Lewis base and Lewis acid, respectively, to synergistically activate NO molecules. Using density functional theory for material screening, P−doped ZnO is predicted to exhibit rather high NOER activity with an ultralow limiting potential (−0.04 V), accompanied by the excellent suppression effect on the competitive side reactions to guarantee its high selectivity for NH3 production. Motivated by the theoretical prediction, the synthesized P−doped ZnO catalyst showed a high NH3 yield rate (218.2 μmol h−1cm−2 at −0.7 V) and a high Faradaic efficiency (91.4 %), as confirmed by our experimental measurements. This work not only suggests a high−performance catalyst for NO reduction but also expands upon the potential applications of FLPs in electrocatalysis.

The limits of ground-state water splitting on ZnO surfaces: A density functional theory study

The water (H2O) splitting reactions towards hydrogen (H2) and oxygen (O2) production in the ground state are here investigated on ZnO catalyst surfaces by means of density functional theory simulations. To this end, the Zn-terminated and O-terminated (0001) and (0001̅) surfaces, respectively, and the non-polar (101̅0) and (112̅0) ones, have been investigated. The reaction thermodynamics has been analysed, being endergonic at normal conditions, and only exergonic at high temperatures and with high partial pressures of reactants. The adsorption of H2O, H2, O2, and reaction intermediates OH, O, and H, underlines the oxophylic character of Zn-terminated (0001) surface, as well as the H-phylic character of O-terminated (0001̅) surface, while non-polar surfaces display both O- and H-phylic centers. The adsorption and co-adsorption strengths and elementary steps energy barriers along the reaction path pinpoint the key reaction limiting steps. The H2 formation step has a prohibitive barrier of 4.91 eV on the (0001̅) surface, and a more moderate barrier of 2.33 and 1.83 eV for the non-polar (101̅0) and (112̅0) surfaces respectively. On the (0001) surface, the rate limiting step is O2 formation, with an energy barrier of 4.94 eV. Regardless of the surface, a higher affinity towards water would be a way to improve the reaction catalysis. The possible modification of surfaces to reduce the energy costs of the limiting steps are discussed, including the use of light-triggered ZnO catalyst, as well as the simultaneous presence of different surfaces to better split the different reaction steps in an energetically more efficient fashion.

Li/La and Cu modified ZnO semiconductor: Highly boosted of dielectric and sunlight-treatment of thiamethoxam and brilliant green contaminants

Solving the global environmental problem which related to the dissolved organic pollutants into water systems is an essential issue for human-health and aquatic life. This study represents the simple synthesis of new Li/La and Cu modified ZnO compositions as active photocatalysts and proper dielectric materials for electrical energy storage devices. The synthesized powders have one phase nature with hexagonal lattice indexed to ZnO structure. The field emission scanning electron microscopy (FESEM) clearly showed that (Li, La) modified ZnO powder consist of a mixture of particles having open hexagonal tube and spherical shapes. The FESEM picture of (Li, Cu, La) modified ZnO powder revealed lumps like cabbage shape mainly composed of pieces like sheets or papers. The purity and elemental composition were also verified by energy dispersive spectroscopy (EDS) analysis. The addition of (Li, La) and (Li, Cu, La) ions to ZnO semiconductor extremely improved the dielectric constant which is a benefit for application in solid state energy storage systems. (Li, Cu, La) modified ZnO sample is a suitable catalyst for removal of organic waste owing to its high response to visible light spectrum with measured band gap energy of 2.76 eV. The synergistic effect of Li+, Cu2+ and La3+ dopants induced high visible light photodegradation activities against thiamethoxam pesticide and brilliant green dye with measured efficiencies of 92 and 96 % after reaction time of 50 min, respectively. The high stability and mineralization properties of (Li, Cu, La) modified ZnO catalyst leads to the conclusion that this composition has a potential use in wastewater treatment.

0D/1D CuO-Cu2O/ZnO p-n heterojunction with high photocatalytic activity for the degradation of dyes and Naproxen

The development of highly active photocatalysts with broad spectrum response is of paramount importance for photocatalytic applications. Herein, heterostructured CuO-Cu2O/ZnO photocatalysts were prepared in a single step and under mild conditions using a photodeposition process which allows to deposit CuO-Cu2O particles with an average size of ca. 2.4 nm on the surface of ZnO nanorods. The p-n heterojunction built between CuO-Cu2O and ZnO allows to increase both the visible light response of the photocatalyst and the charge separation. The CuO-Cu2O(10%)/ZnO catalyst exhibits the highest activity for the degradation of dyes (Rhodamine B and Remazol Brilliant Blue R) and of Naproxen under simulated solar light irradiation. Based on scavenging experiments, holes, superoxide radicals O2●- and singlet oxygen 1O2 are the dominant species involved in the photocatalytic degradation and a mechanism is proposed. Due to its high stability and photocatalytic performance in various water matrices, the CuO-Cu2O(10%)/ZnO nanohybrid is of high potential for the large scale remediation of organic pollutants in wastewater.

Influence of FRET, charge separation, and density of defect states on the improvement of UV light-driven photocatalytic activity of PMMA capped ZnO nanomaterials

This study employs oxidative polymerization, co-precipitation, and ex-situ surface capping techniques to fabricate pristine PMMA, ZnO, and PMMA-capped ZnO specimens with varying PMMA concentrations. X-ray diffraction reveals reduced directional growth of ZnO, while Fourier transform infrared spectroscopy confirms PMMA chain bonding with ZnO in PMMA-capped specimens. Scanning electron microscopy illustrates decreased average length and thickness of ZnO nanoplates post-surface modification, indicating a robust interaction between PMMA and ZnO. X-ray photoelectron spectroscopy identifies suppressed defects, including zinc interstitials and oxygen vacancies, affirming ZnO surface capping by PMMA. Absorption spectra display a blue shift in band-edge or increased bandgap, attributed to the combined effects of band alignment offset and reduced oxygen vacancy states. Luminescence spectra show gradual quenching linked to PMMA content increase, with defect-related emission suppression attributed to ZnO surface capping. UV emission suppression is ascribed to donor concentration-dependent Förster resonance energy transfer (FRET) from PMMA to ZnO. Photocatalytic tests reveal enhanced efficiency in PMMA-capped ZnO catalysts attributed to synergies involving charge separation, bulk recombination centers, oxygen vacancy states, and FRET. Efficiency improves with higher PMMA content, aligning with changes in emission intensity. The study demonstrates emission intensities' tunability through surface capping and donor concentration-dependent FRET, ultimately influencing degradation efficiency.

Optical behavior, TL defect center analysis and photocatalytic characterization of Ag2O doped ZnO nano crystals

The objective of the study is to prepare Ag+-dopedZnO nano crystals and to assess their structure, optical behavior, TL analysis, photocatalytic activity. Using sol–gel technique the Ag+-doped ZnO nano crystals prepared. Using the FT-IR, XRD, BET surface area, SEM, EDX characterization techniques, we have examined the structure of the developed samples. The TL analysis of samples was done under a dose of 25 kGy gamma irradiation. Trap depth parameters of the samples evaluated. Which suggested the ZnO nano crystals doped with Ag+ ions are purely TL active. The optical studies such optical absorption, photoluminescence of samples reveal their optical behavior. The optical band gap of the samples also evaluated. Which is increasing with increase in concentration of Ag+ ions in ZnO nano crystals. Using the MV (10 ppm) and CR (10 ppm) dyes, under visible light the photocatalytic activity of the samples reported. At a reaction period of 90 min, the nano powdercontaining 1.0 mol% Ag+-dopedZnO nano crystals and a band gap energy of 2.75 eV demonstrated the best photocatalyticefficiency (∼91 %) in both colors. The evaluationwas done on the impact of radical scavenger research and catalyst dosage on degrading efficiency. The rate of reaction in the presence of 1.0 mol% Ag+-dopedZnO nano crystals was four times higher than the ZnO catalyst's rate constants, and the degradation reaction follows pseudo-first-orderkinetics. The degrading process shows pseudo-first-order kinetics, and the reaction rate was four times higher than the ZnO catalyst in the presence of 1.0 mol% Ag+-dopedZnO nano crystals. It took three cycle runs for the degrading efficiency to drop by 1 %. Thus, 1.0 mol% Ag+-dopedZnO nano crystals was employed as a promising photocatalyst with strong reusability potential for the degradation of textile colors, which will be very beneficial.

Effective visible light-driven binary ZnO catalyst decorated on layered double hydroxides for simultaneous photocatalytic degradation of Ciprofloxacin and Ampicillin

BackgroundThe direct use of clean solar energy to convert organic pollutants in industrial wastewater into harmful products is a viable tactic and a hot topic to save water bodies and avoid water pollution. Pharmaceutical wastewater is complicated and contains a variety of contaminants, making its treatment difficult. MethodThis study focuses on the simultaneous degradation of an aqueous solution containing a combination of contaminants, Ampicillin (AMP) and Ciprofloxacin (CIP). Using hydrothermal process, we successfully fabricated a ZnO-NiCoMn layered double hydroxide (LDH) sheet. The prepared catalyst was examined using a range of surface analytical optical techniques. Significant findingsThe ZnO-NiCoMn LDH demonstrates exceptional photocatalytic performance, as demonstrated by the maximal CIP and AMP degradation rates of 96 % and 94 % in 100 min under visible light, respectively, according to the data. ZnO-adorned NiCoMn LDH sheets exhibited a rod-like structure, as demonstrated by FE-SEM and HR-TEM. Because of the highest charge separation and superior electron (e−) transport between ZnO and NiCoMn LDH material, the binary catalyst degraded CIP and AMP by 96 % and 94 % in 100 min, respectively, more than the bare catalyst. The binary ZnO-NiCoMn LDH catalyst could withstand up to five CIP and AMP degradation cycles.

Boosting propane dehydrogenation of defective S-1 stabilized single-atom Pt and ZnO catalysts via coordination environment regulation

Boosting propane dehydrogenation of defective S-1 stabilized single-atom Pt and ZnO catalysts via coordination environment regulation

Crystal facet-dependent CO2 cycloaddition to epoxides over ZnO catalysts

Crystal facet-dependent CO2 cycloaddition to epoxides over ZnO catalysts

Ternary Zn-Ce-Ag catalysts for selective and stable electrochemical CO2 reduction at large-scale

Catalyst materials with high stability and selectivity, based on inexpensive materials, are vital for practical electrochemical carbon dioxide (CO2) reduction (ECR). In this study, we report ternary Zn-Ce-Ag catalysts for selective and stable CO2-to-CO conversion at high current densities on a large scale. We found that ZnO catalysts are relatively selective for CO2-to-CO conversion, but are only stable for less than 20 h at current densities over 100 mA cm−2 due to the reduction of the Zn oxide phase, along with the ECR. Combining ZnO with CeO2 significantly improves the stability of the catalysts, maintaining a CO Faradaic efficiency (FECO) of 80 % for 100 h at the current density of 200 mA cm−2. By introducing a small amount of silver (<10 wt%) to form ternary Ag-Ce-Zn catalysts, both CO selectivity and stability are significantly improved: the developed catalysts exhibit a high FECO of 90 % at 200 mA cm−2 and are stable for 200 h. We attribute the enhanced CO2-to-CO conversion efficiency to the abundance of stable interfacial areas of various metal-oxide interactions, which are critical for ECR. To demonstrate the potential for practical application, we performed the ECR in a large electrochemical cell, with an active surface area of 100 cm2. The system delivers a FECO of 90 % at 200 mA cm−2 for an extended operation time of 200 h.

Photocatalysis and irradiative TL defect center analysis studies of Cu2+ ionic ZnO nano lattice

The objective of the study is to create a series of ZnO nano powders doped with CuO using sol–gel technology in order to look into their photocatalytic activity for the photodegradation and cleaning process. XRD, BET surface area, surface morphology, chemical analysis, and FT-IR measurements have all been used to look at the nano powders' structure from this point of view. The results suggest that the materials were made at the nanoscale level, and their hexagonal shape makes them good as catalytic nano resources. Photoluminescence and UV–visible diffusion reflection spectroscopy were also used to test the nano powders. The results show that the nano powders that were made are visually active. To find out how photocatalytic the nanoparticles are, they were used to break down CR (10 ppm) and MV (10 ppm) dyes when exposed to light. The nano powder with 1.0 mol% of CuO doped ZnO nanoparticles had the highest photocatalytic efficiency (86 %). It had a band gap energy of 3.15 eV and reacted with both dyes for 90 min. Researchers looked at radical scavengers and the effect of catalyst dose on how well they broke down substances. The reaction that broke down had pseudo-first-order kinetics, and the rate of the reaction was four times faster when 1.0 mol% Cu was added to the ZnO catalyst. The degradation efficiency only dropped by 1 % after three rounds of the process. Because of this, the 1.0 mol% Cu-ZnO was used as a photocatalyst that broke down textile dyes well and had a lot of promise to be used again. The samples were also checked for thermoluminescence while they were exposed to 25 kGy of gamma radiation. Samples were tested for their trap depth characteristics, indicating the test samples' potential for TL activity.

Sol-Gel technique, characterization and photocatalytic degradation activity of Manganese doped ZnO nanoparticles

Photocatalysis using semiconductor metal oxide stands out as a highly effective and efficient method for eliminating organic pollutants from wastewater. This study aims to assess the photocatalytic capabilities of Mn doped ZnO nanocomposites in degrading methylene blue (MB) dye under ultra-violet light exposure. This study details the synthesis of ZnO photocatalysts through a straightforward one-step sol-gel method, incorporating varying levels of Mn-doping (0%, 2% &amp; 4%). The structural and optical attributes were examined using techniques such as powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and UV-Vis diffuse reflectance spectra. X-ray diffraction analyses verified the presence of a hexagonal wurtzite crystal structure in all synthesized samples, exhibiting a high degree of crystallinity. In addition, an investigation into the impact of Mn impurities on the photocatalytic performance of ZnO catalysts was conducted in the context of methylene blue (MB) degradation. The experimental findings revealed that the Mn doped ZnO nanoparticles produced exhibited significantly superior photocatalytic performance compared to pure ZnO when used in breaking down methylene blue under UV-light exposure. This study proposes that these Mn doped ZnO could serve as a highly effective photocatalyst for treating water contaminated with certain chemically persistent synthetic organic dyes. The improved photocatalytic capabilities of ZnO nanostructures doped with Mn were ascribed to the synergistic impact of increased surface area in ZnO nanosphere and enhanced efficiency in charge separation resulting from optimized Mn doping. A potential explanation for the heightened photocatalytic performance of Mn-doped ZnO nanostructures is proposed tentatively.

Enhanced photocatalytic activity of FeSO4 in a ZnO photocatalyst with H2O2 for dye degradation

In this study, the photocatalytic degradation efficiency of ZnO synthesized by a hydrothermal method and iron-supported ZnO catalysts by an impregnation method, dried (D) and calcined (C), was evaluated, through the degradation of methylene blue (MB) and methyl orange (MO) molecules under UV irradiation. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, and UVvisible diffuse reflectance spectroscopy (DRS). XRD showed that FeSO4 is supported on ZnO, and the XPS study revealed higher concentrations of hydroxyl groups and Fe3+ for the dried catalyst. The bandgap energies were 3.24, 3.23, and 3.19 eV for ZnO, Fe/ZnO D and Fe/ZnO C, respectively. The results revealed that Fe/ZnO D with H2O2 exhibited a higher photocatalytic degradation efficiency than ZnO, achieving 97% and 99% degradation for MB and MO at 10 min, which implies that the integrated iron in ZnO serves as an electron-hole separator. In addition, the catalyst has a larger BET specific area, the presence of hydroxyl groups and sulfate ions on the surface of the catalyst with holes forms hydroxyl radicals (•OH), and the presence of Fe3+ on the surface catalyst with H2O2 produces more •OH radicals. •OH radicals are the major oxidation species in this process, which promotes the degradation of dyes. The photocatalytic dye degradation efficiency was also evaluated for various catalyst doses, dye concentrations and solution pH values. Moreover, the stability of the catalyst over repeated cycles of dye treatment was demonstrated.

Biological Renewable Cellulose-Templated Zn1-XCuXO/Ag2O Nanocomposite Photocatalysts for the Degradation of Methylene Blue.

Herein, Cellulose-templated Zn1-XCuXO/Ag2O nanocomposites were prepared using biological renewable cellulose extracted from water hyacinth (Eichhornia crassipes). Cellulose-templated Cu-doped ZnO catalysts with different amounts of Cu as the dopants (1, 2, 3, and 4%) were prepared and denoted CZ-1, CZ-2, CZ-3, and CZ-4, respectively, for simplicity. The prepared catalysts were tested for the degradation of methylene blue (MB), and 2% Cu-doped ZnO (CZ-2) showed the best catalytic performance (82%), while the pure ZnO, CZ-1, CZ-3, and CZ-4 catalysts exhibited MB dye degradation efficiencies of 54, 63, 65, and 60%, respectively. The best catalyst (CZ-2) was chosen to further improve the degradation efficiency. Different amounts of AgNO3 (10, 15, 30, and 45 mg) were used for the deposition of Ag2O on the surface of CZ-2 and denoted CZA-10, CZA-15, CZA-30, and CZA-45, respectively. Among the composite catalysts, CZA-15 showed remarkable degradation efficiency and degraded 94% of MB, while the CZA-10, CZA-30, and CZA-45 catalysts showed 90, 81, and 79% degradation efficiencies, respectively, under visible light within 100 min of irradiation. The enhanced catalytic performance could be due to the smaller particle size, the higher electron and hole separation and charge transfer efficiencies, and the lower agglomeration in the composite catalyst system. The results also demonstrated that the Cu-doped ZnO prepared with cellulose as a template, followed by the optimum amount of Ag2O deposition, could have promising applications in the degradation of organic pollutants.

Enhanced Methanol Synthesis from CO2 Hydrogenation Achieved by Tuning the Cu-ZnO Interaction in ZnO/Cu2O Nanocube Catalysts Supported on ZrO2 and SiO2.

The nature of the Cu-Zn interaction and especially the role of Zn in Cu/ZnO catalysts used for methanol synthesis from CO2 hydrogenation are still debated. Migration of Zn onto the Cu surface during reaction results in a Cu-ZnO interface, which is crucial for the catalytic activity. However, whether a Cu-Zn alloy or a Cu-ZnO structure is formed and the transformation of this interface under working conditions demand further investigation. Here, ZnO/Cu2O core-shell cubic nanoparticles with various ZnO shell thicknesses, supported on SiO2 or ZrO2 were prepared to create an intimate contact between Cu and ZnO. The evolution of the catalyst's structure and composition during and after the CO2 hydrogenation reaction were investigated by means of operando spectroscopy, diffraction, and ex situ microscopy methods. The Zn loading has a direct effect on the oxidation state of Zn, which, in turn, affects the catalytic performance. High Zn loadings, resulting in a stable ZnO catalyst shell, lead to increased methanol production when compared to Zn-free particles. Low Zn loadings, in contrast, leading to the presence of metallic Zn species during reaction, showed no significant improvement over the bare Cu particles. Therefore, our work highlights that there is a minimum content of Zn (or optimum ZnO shell thickness) needed to activate the Cu catalyst. Furthermore, in order to minimize catalyst deactivation, the Zn species must be present as ZnOx and not metallic Zn or Cu-Zn alloy, which is undesirably formed during the reaction when the precatalyst ZnO overlayer is too thin.

Modified Cu–ZnO Catalysts Supported on the Mixture of ZnO and Zn–Al Oxide for Methanol Production via Hydrogenation of CO and CO2 Gas Mixture

Modified Cu–ZnO Catalysts Supported on the Mixture of ZnO and Zn–Al Oxide for Methanol Production via Hydrogenation of CO and CO2 Gas Mixture

Photocatalytic degradation of oxytetracycline using ZnO catalyst

AbstractIn the present study, the degradation of oxytetracycline (OTC) under ultraviolet (UV) light in the presence of ZnO catalyst was investigated, and optimum parameters for degradation efficiency were determined. Different pH values, ZnO dosages, reaction times, OTC concentrations, and UV lights were used in this study. The optimum conditions found were as follows: pH 4, ZnO 1 g L−1, reaction time 25 min, and OTC concentration 10 mg L−1. Degradation efficiency was 42.1%, 76%, 70.7%, and 61.7% for ZnO and photocatalytic (for UV‐A, UV‐B, and UV‐C) degradation at optimal conditions, respectively. The resulting products after the photocatalytic oxidation of OTC were determined in the study. To identify the toxicity of degradation products and OTC, the lowest LC 50 (50% lethal concentration) and EC 50 (50% effective concentration) values were found. The resulting ethanamine, 2‐(2,6‐dimethylphenoxy)‐N‐methyl‐ by‐products were observed to be more toxic than OTC. Furthermore, it was seen that isopropoxy carbamic acid, ethyl ester by‐products were formed, whose presence is environmentally risky for aquatic environments due to their low EC50 values.