Addition Of ZrO2 Research Articles

Engineered Polystyrene‐Zirconium Dioxide Nanocomposite With Enhanced Optical Properties

ABSTRACTThe demand for transparent polymers with high‐refractive indices (RIs) is increasing due to their versatility; however, low RIs also hold significance. Engineering the RI of polymer nanocomposites is crucial which benefits industry and research. The study investigates the influence of ZrO2 nanoparticles on the optical and surface properties of the polystyrene matrix. UV–Vis spectroscopy confirms that transparency is maintained with a light transmittance of 90 even with a ZrO2 loading of 16 wt%, while ellipsometry shows a steady increase in the RI due to the incorporation of nanoparticles. The RI of composites exceeds that of pure polystyrene (RI: 1.3–1.7) and utilizes the RI of ZrO2 (> 2.00) without altering the sample thickness. The microscopic image shows uniform distribution of particles up to 8 wt%, with slight agglomeration at higher contents. Scanning electron microscopy examination shows that the ZrO2 nanoparticles (20–150 nm) form loose agglomerated structures, while atomic force microscopy examination shows aggregate formation at 16 wt%. The addition of ZrO2 increases the surface roughness and water contact angle up to 4 wt%, which is related to the concentration of the nanofiller and the minimal interaction between ZrO2 and water. The results demonstrate the potential of ZrO2‐loaded nanocomposites for applications requiring high RIs and optical transparency.

Calcium aluminate cement: a study on the effect of additives for dental applications

Recent dental material advancements have sparked increased interest in dental cements due to their natural tooth-like appearance, biocompatibility, and stability. These cements hold potential in dental fillings, enamel and root protection, and connecting dental implants. However, no single cement fulfills all application needs, necessitating multiple types. Ideal dental cements require resistance to degradation, strong bonding, high strength, fracture toughness, and optical transparency for imaging. In this study, the effect of the addition of ZrO2, Bi2O3, and ZnO on the mechanical was the solid-state method was used for the synthesis of calcium aluminate (C3A) cement powder, and additives of zirconia, bismuth oxide and zinc oxide were added at magnitudes of 10 wt.% and 20 wt.%. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), setting time, compressive strength (CS), Scanning electron microscopy (SEM) microscopy, and radiopacity evaluation (RE) were performed for characterization and properties evaluations. With the formation of a new phase, C3ZA2, the compressive strength increased by up to 275% by reducing porosity and stabilizing phase transitions during hydration. The evidence showed that the amount of bismuth oxide and zirconia additive have high optical (7 and 3.5 mmA) and biological properties and a significant impact on strength in dental applications.

Low‐Coordination Crystallographic Lattice Engineering to Discover Ce3+‐Activated Ultra‐Wide Visible‐to‐Near‐Infrared Luminescent Materials

AbstractDevelopment of ultra‐broadband visible‐to‐near‐infrared (VIS‐NIR) luminescent materials is a challenging but rewarding endeavor, as they are highly desirable for a number of applications in photonics, optoelectronics, and biological sciences. Nevertheless, to date, rare earth‐doped phosphors that can be efficiently excited by blue light and produce broadband emission in the VIS‐NIR regions remain scarce. In this study, a series of Ce3+‐doped Ba3M4O9 (M = Sc, Lu, Y) broadband luminescent materials are designed based on low‐coordination crystallographic lattice engineering. Among these materials, Ba3Y4O9:Ce3+ produces a continuous ultra‐wide VIS‐NIR emission (λem = 660 nm) in the range of 500–950 nm under 410 nm light excitation. This emission wavelength is the longest among those observed in Ce3⁺‐doped oxide materials. Structural refinement, theoretical calculation, and spectral analysis demonstrate that this VIS‐NIR broadband emission is attributed to the occupying multiple distorted octahedral lattice sites by Ce3+ in Ba3Y4O9. Several strategies are employed to enhance the luminescence intensity and thermal stability of this material, including the use of carbon paper coating, the incorporation of co‐solvents, and the addition of GeO₂ or ZrO₂. Furthermore, the as‐prepared materials demonstrate multifunctional applications in white light‐emitting diodes (WLED), night vision, and fluorescent thermometers. This study offers insights into the design of Ce3+‐doped ultra‐wide VIS‐NIR light‐emitting materials.

A comparative study for optimizing photocatalytic activity of TiO2-based composites with ZrO2, ZnO, Ta2O5, SnO, Fe2O3, and CuO additives

Despite the widespread use of titanium dioxide (TiO2) in photocatalytic applications, its inherent limitations, such as low efficiency under visible light and rapid recombination of electron-hole pairs, hinder its effectiveness in environmental remediation. This study presents a comparative investigation of TiO2-based composites, including TiO2/ZrO2, ZnO, Ta2O3, SnO, Fe2O3, and CuO, aiming to assess their potential for enhancing photocatalytic applications. Photocatalysis holds promise in environmental remediation, water purification, and energy conversion, with TiO2 being a prominent photocatalyst. To improve efficiency and broaden applicability, various metal oxide composites have been explored. Composites were synthesized and characterized using techniques such as XRD, SEM, TEM, and zeta potential analysis to evaluate their structural and morphological properties. Photocatalytic performance was assessed by degrading herbicide Imazapyr under UV illumination. Results revealed that, the photo-activity of all prepared composites were more effective than the photo-activity of commercial hombikat UV-100. The photonic-efficiency is arranged according to the order TiO2/CuO > TiO2/SnO > TiO2/ZnO > TiO2/Ta2O3 > TiO2/ZrO2 > TiO2/Fe2O3 > Hombikat TiO2-UV100. All composites exhibited superior performance, attributed to enhanced light absorption and charge separation. The study underscores the potential of these composites for environmental remediation and energy conservation, offering valuable insights for the development of advanced photocatalysts.

Densely packed glass structure caused by seven-coordinated Zr in high elastic modulus Al2O3–SiO2–ZrO2 glasses

Al2O3–SiO2–ZrO2 ternary glasses were fabricated using a levitation technique. The addition of ZrO2 to the Al2O3–SiO2 glasses strongly affected their thermal, mechanical, and structural properties. Several compositions were partially vitrified at the laser-melted area without levitation although their melting required temperatures higher than 2000 °C. With increasing ZrO2 content, the elastic moduli linearly increased, and the 50Al2O3–20SiO2–30ZrO2 glass exhibited a Young′s modulus of 166 GPa and Vickers hardness HV of 10.6 GPa. Conversely, crack resistance significantly decreased with the addition of ZrO2. Density measurements, Zr L2,3-edge and K-edge X-ray absorption fine structure analyses, and 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectroscopy were performed to investigate the local structure around Zr, Al, and Si in the glasses. Zr formed distorted ZrO7 as in monoclinic ZrO2, which has been rarely found in conventional oxide glasses. The highly oxygen-coordinated Al atoms such as AlO5 and AlO6, were the main components in the glasses rather than AlO4. The majority of Si atoms form SiO4 with four bridging oxygen (Q4). Among the four bridging oxygens, the number of oxygens connected to Al or Zr clearly increased with decreasing SiO2 content. The high packing density of the ternary glasses that resulted in high elastic moduli originated from the highly oxygen-coordinated Zr and Al and their close bonding with SiO4 without generating nonbridging oxygens.

The effect of ZrO2 on the structure, properties and crystallization behavior of transparent lithium disilicate based glass-ceramics

The effects of ZrO2 on the parent glass network structure, crystallization behavior, and properties of lithium aluminosilicate glass-ceramics by various amounts of ZrO2 were investigated. The main crystalline phases of transparent glass-ceramics are quartz solid solution and Li2Si2O5. The increase of ZrO2 addition promotes an increasing of Q3(Zr) tetrahedral proportion in the glass network, resulting a reduction of ZrO2 nucleus. The increase of ZrO2 content also effectively improves the fracture toughness of glass-ceramics, but reduces the transmittance significantly. In this work, the glass with the 1 mol% ZrO2 nucleated at 545 °C for 2 h and crystallized at 800 °C for 2h possesses the excellent comprehensive properties, which exhibited the Vickers hardness of 6.91 GPa, the fracture toughness of ∼1.40 MPa·m1/2, and the transmittance at 550 nm of 90 %. It provides significant potential applications in the display protective cover.

Application of ZrO2 and Ni modified carbon nanotube composites as bifunctional water electrolysis catalysts

By using carbon nanotube (CNT) as the carrier, Ni as the active center and ZrO2 as the modifier, an efficient electrocatalytic material (ZrO2-Ni/CNT) is designed and synthesized in this paper. The structure and properties of the catalyst are characterized by various instrumental analysis methods such as SEM, TEM, XRD and XPS. The electrochemical test results show that the addition of ZrO2 can significantly improve the catalytic performance of this catalyst in the electrochemical water splitting. In an alkaline solution, ZrO2-Ni/CNT catalyst displays an exceedingly low overpotential of 169 mV and 249 mV at the current density of 10 mA cm−2 towards hydrogen evolution reaction and oxygen evolution reaction, respectively. This work shows that the modification of ZrO2 can improve the electrocatalytic activity of Ni-based materials, and the modification strategy can be applied to improve the electrocatalytic activity of commercial Ni-based electrode materials.

Effect of Zr4+ on the microstructure and electrical properties of 0.6Y2O3-0.4YCr0.5Mn0.5O3 NTC ceramics

In this study, 0.6Y2O3-0.4YCr0.5Mn0.5O3 negative temperature coefficient (NTC) ceramics doped with different ZrO2 contents were prepared using a two-step sintering method. The effects of Zr4+ content on the microstructure and electrical properties of 0.6Y2O3-0.4YCr0.5Mn0.5O3 were mainly investigated. For the microstructure, X-ray diffraction (XRD) reveals the presence of two main crystalline phases in the samples: Y2O3 and YCr0.5Mn0.5O3. Scanning electron microscopy (SEM) reveals a clear two-phase appearance, and the porosity tends to decrease with the addition of ZrO2. Combined with energy dispersive spectrometer (EDS) to derive the distribution of the elements, Zr4+ is mainly present in the Y2O3 phase, with a small amount in the YCr0.5Mn0.5O3 phase. In addition, the grain sizes of different groups were counted, and the grain size of Y2O3 decreased from 2.73 ± 1.80 μm to 1.65 ± 0.93 μm with the increase of ZrO2 content. For the electrical properties, the resistance-temperature curves were measured from 298.15 K to 1073.15 K, and all the samples exhibited NTC characteristics. And with the increase of ZrO2 content, the resistivity increased from 1.91 × 107 Ω cm to 1.96 × 108 Ω cm, and the B25/100 value decreased from 3315 K to 1310 K. In addition, the chemical state forms of the elements on the surface of the samples were analysed by X-ray photoelectron spectroscopy (XPS), and the valence states as well as the occupancy of the transition elements Cr and Mn were analysed in detail according to the principle of multiple splitting. Finally, the mechanism of influence on microstructure and electrical properties is explained by combining the theory of grain boundary migration and thermal ceramic conductivity.

Electrochemical production of zirconium silicides from KCl–K<sub>2</sub>SiF<sub>6</sub>–ZrO<sub>2</sub> melt

The unique properties of zirconium silicides attract the attention of a large number of authors from various scientific fields. Expansion of application methods also poses the challenge of developing new, more environmentally friendly and affordable methods of production. The most environmentally friendly method without equipment requirements is the electrolysis of the molten salt. The work proposes a method for producing zirconium silicides by electrolysis of the KCl–K2SiF6–ZrO2 melt. In order to substantiate the electrolysis parameters, the kinetics of cathodic reduction was studied and the limiting stage of the process was determined. The structure and phase composition of the cathode deposit were studied using X-ray diffraction and electron scanning microscopy. In the course of the work, conclusions were drawn about the change in the content of the ZrO2 additives on the morphology of the sediment, and it was also suggested that it was possible to obtain zirconium silicides from more accessible raw materials, such as zircon.

Assessing the impact of Ag: TiO2 and Ag: ZrO2 nanoparticles on the flexural strength of self-cured denture base resin

Abstract This study investigates the effect of silver, titanium dioxide, and silver, Zirconium dioxide nanoparticles on the flexural strength of self-cured denture base resin. The samples were divided into four groups according to the addition of different nanoparticles to the self-cured acrylic PMMA. Control group A, reinforcement group B (Ag + TiO2), reinforcement group C (Ag + ZrO2) and reinforcement group D (Ag + TiO2 + ZrO2). The samples were again divided into three subgroups according to the nanoparticulate addition ratio of 0.1, 0.3 and 0.5 wt.% TiO2 and ZrO2 each with a fixed ratio of 0.3wt.% Ag as antimicrobial. Excluding group D addition, it was 0.05, 0.15, 0.25 wt.% for both TiO2 and ZrO2 with 0.3 wt.% Ag. After immersing the samples in distilled water for 48h, the flexural strength was measured using the three-point bend test. Evaluation of flexural strength showed a significant decrease with an increasing percentage of nanoparticles, except the increase in the percentage of additions of ZrO2 showed an increase in flexural strength. The samples underwent X-ray diffraction examination and FESEM to describe nanoparticles and examine the structure of acrylic samples. X-ray diffraction revealed the absence of mistake diffraction, indicating high crystal structure purity. In addition, images from the scanning electron microscope showed a homogeneous distribution of nanoparticles within the acrylic structure. Maximum flexural strength was seen in the 0.3 wt.% Ag-0.15 wt.% TiO2-15 wt.% ZrO2 and minimum in 0.3 wt.% Ag -0.5 wt.% TiO2. The modified samples also exhibited colour changes. We conclude flexural strength value depends on the percentage of additions and type of nanoparticles.

Effect of ZrO2 Particles on the Microstructure and Ultrasonic Cavitation Properties of CoCrFeMnNi High-Entropy Alloy Composite Coatings

CoCrFeMnNi-XZrO2 (X is a mass percentage, X = 1, 3, 5, and 10) high-entropy alloy composite coatings were successfully prepared on 0Cr13Ni5Mo martensitic stainless steel substrates using laser cladding technology. The phase composition, microstructure, mechanical properties, and cavitation erosion behavior of the composite coatings under different contents of ZrO2 were studied. The mechanism of ZrO2 particle-reinforced cavitation corrosion resistance was studied using ABAQUS2023 finite element software. The results show that the phase structure of the composite coating organization is composed of FCC phase reinforced by ZrO2 phase. The addition of ZrO2 causes lattice distortion. The coatings have typical branch crystals and an equiaxed crystal microstructure. With the increase in ZrO2 content, the microhardness of the composite coatings gradually increases. When X = 10%, the coating’s microhardness reached 348 HV, which was 95.53% higher than the high-entropy alloys without ZrO2 added. Adding ZrO2 can prolong the incubation period of high-entropy alloys; the high-entropy alloy composite coating with 5 wt.% ZrO2 exhibited the best cavitation resistance, with a cumulative volume loss rate of only 15.74% of the substrate after 10 h of ultrasonic cavitation erosion. The simulation results indicate that ZrO2 can withstand higher stress and deformation in cavitation erosion, reduce the degree of substrate damage, and generate higher compressive stress on the coating surface to cope with cavitation erosion.

Enhanced random vector functional link based on artificial protozoa optimizer to predict wear characteristics of Cu-ZrO2 nanocomposites

Owing to the absence of scientific methods for predicting nanocomposites' wear rates, a freshly updated machine learning method that uses an Artificial Protozoa Optimizer (APO) to forecast the tribological performance of Cu-ZrO2 nanocomposites was proposed. The updated model was used to predict the coefficients of friction and wear rates of Cu-ZrO2 nanocomposites produced in this work. Copper-zirconia nanocomposite powders were fabricated utilizing the ball milling process, varying in milling time and ZrO2 weight percentage. The effect of reinforcement percentage and milling time on the morphology and microstructure of the copper composite powders was characterized. The study concentrated on the effects of high-energy ball milling on the morphology, microstructure, and microhardness of the resulting composites. After cold compaction at 700 MPa of pressure, the resultant powders were sintered for 2 h at 950 °C in a hydrogen atmosphere. Based on the results, a 20-h milling time is the best option for creating a Cu-ZrO2 nanocomposite with evenly distributed reinforcement. The microhardness and wear rate of the Cu-15%ZrO2 nanocomposites are improved by 66.2 %, and 81.1 %, respectively, when compared to pure copper. The crystallite size decreases significantly with the addition of ZrO2, reaching 32.5 and 11.1 nm for samples containing 5 and 15 % weight percent ZrO2. That is why there is a rise in wear and mechanical properties. For Cu-ZrO2 nanocomposites with reinforcement content up to 15 %, the model constructed using the APO method demonstrated excellent forecasting of the wear rate and coefficient of friction.

Fabrication of Hybrid Epoxy Composites (Joint Compound Adhesive) for Aluminum Substrate Applications and Their Evaluation for Mechanical Properties.

This research endeavor deals with the development of an epoxy hybrid nanocomposite using aliphatic diglycidyl ether of a bisphenol A (DGEBA) epoxy matrix. The formulation used the stoichiometric ratio of the curing agent and incorporated nanopigments such as zirconium and silica, along with other microfillers. We incorporated Zr and SiO2 nanoparticles and various other additives in the epoxy matrix and ensured homogeneous dispersion by using sonication methodology along with silane as a coupling agent. Aluminum molds were utilized to fabricate dumbbell-shaped ASTM standard samples for the testing of mechanical properties. The adhesive properties were evaluated through standard lap shear tests. Fourier transform infrared spectroscopy was utilized to analyze the cross-linking reaction of the epoxy moiety and the polyamidoamine adduct curing agent. Further characterization using field emission scanning electron microscopy, energy-dispersive spectroscopy, and high-resolution transmission electron microscopy confirmed the presence and uniform dispersion of the fillers and nanopigments. The results showed good enhancements in ultimate tensile strength, yield strength, and elastic modulus of 95.3, 162.1, and 425.4%, respectively, compared to formulations using only SiO2. The addition of ZrO2 and SiO2, along with various microfillers, such as talc and aluminum silicate, led to significant improvements in the mechanical properties. This study demonstrates the synergistic efficiency of combining SiO2 and ZrO2 along with microfillers, such as talc and aluminum silicate, in epoxy resin for diverse applications in the construction industry, where mechanical strength and substrate adhesion are crucial.

Investigation of in-vitro bioactivity, electrochemical corrosion, wettability and adhesion properties of bioglass-based coatings modified with Y2O3 and Zr on novel β-type Ti-30Zr-5Mo alloys

In this study, the in-vitro bioactivity, electrochemical corrosion resistance, wettability, and adhesion properties of bioglass-based coatings modified with Y2O3 and ZrO2 on Ti-30Zr-5Mo alloy were investigated. The coatings were prepared using the sol-gel method and applied to the alloy substrates through dip-coating. The surface morphology and elemental composition of the coatings were analyzed using SEM/EDS and XRD techniques. Potentiodynamic polarization (PDS) and electrochemical impedance spectroscopy (EIS) were employed to assess the electrochemical behavior of the coatings under in-vitro conditions. Contact angle measurements were conducted to evaluate the wettability of the surfaces. Adhesion strength was measured using tensile testing in accordance with ISO 13779-2 standards. Bioactivity tests were performed by immersing the samples in simulated body fluid (SBF). The results demonstrate that the addition of Y2O3 and ZrO2 improves adhesion strength and corrosion potential, but introducing localized galvanic effects that increase the corrosion current density. Besides, the coatings maintained their structural integrity after the bioactivity tests, and promoted new apatite formation.

Processing of Zirconium Oxide Raw Materials to Produce Zirconium Silicides via Electrolysis of KCl-K2SiF6-ZrO2 Melt

The possibility of electrochemical synthesis of zirconium silicides by electrolysis of KCl-K2SiF6 melt with ZrO2 additives at 790 °C has been studied. To determine the synthesis parameters, the kinetics and some features of the mechanism of the cathodic process in the investigated melt on glassy carbon were studied by cyclic chronovoltammetry and chronoamperometry. It was shown that the electroreduction of silicon ions in the KCl-K2SiF6 melt takes place at potentials from 0 to −0.2 V. Additional peaks at more negative potentials were obtained on the voltametric dependences, presumably related to the reduction of zirconium ions and the co-reduction of silicon and zirconium ions. Electrolysis of KCl-K2SiF6 melt with additions of 0.33 and 0.66 wt% ZrO2 in galvanostatic mode at cathodic current density of 20 mA cm−2 was performed in order to check assumptions. Cathode deposits were obtained, which were analyzed by X-ray diffraction and scanning electron microscopy after separation of salt residues. It is shown that the precipitates were represented by zirconium silicides (ZrSi2, ZrSi) as well as oxides (SiO2, ZrO2).

Influence of Graphite and Zirconia Addition on the Tribological Properties of Plasma-Sprayed Alumina Coatings

Al2O3, Al2O3-graphite and Al2O3-ZrO2 coatings were formed on the C45 steel rolls using atmospheric plasma spraying. The influence of graphite and zirconia addition on the surface morphology, phase composition and tribological properties under dry sliding conditions using 30 N load were analyzed. It was found that the addition of graphite or ZrO2 slightly affected the fraction of the α-Al2O3 and γ-Al2O3 phases in the alumina coatings. The highest mass loss rate (~8.84 × 10−4 g/s) was obtained for the friction pair of C45 steel roll and steel plate. The friction coefficient of the Al2O3-graphite coating was slightly lower (up to 7%) compared to the coating of Al2O3-ZrO2. However, the friction pair of Al2O3-ZrO2 coating and steel plate demonstrated the highest wear resistance under dry sliding conditions. The increase in the wear resistance of the Al2O3-graphite and Al2O3-ZrO2 coatings is due to the formation of tribofilm in the sliding contact zone.

Performance improvement of NiO/YSZ sensitive electrode for high temperature electrochemical NOx gas sensors

In the mixed-potential gas sensor, the electrode type, particle size, microstructural morphology, as well as the interface state between the oxide-sensitive electrode and the solid electrolyte, are the key factors for determining the magnitude of the mixed potential. NiO-based material with the addition of Y2O3-stabilized ZrO2 (YSZ) particles is considered as one of the promising sensitive electrode materials for preparing the mixed-potential NOx sensors due to its excellent gas sensitivity. In this paper, the preparation technology of NiO-sensitive electrodes is developed and optimized for improving NOx (NO and NO2) gas-sensitivity properties of the NOx sensors. The experimental results show that the addition of YSZ can effectively improve the agglomeration morphology of NiO particles in the NOx-YSZ-based electrode material during high temperature sintering (i.e. 1200 °C) and enhance the bonding strength with the solid electrolyte. The sensor which was prepared by using the developed NOx-YSZ-based electrode material with the YSZ addition of 20 wt% has the most sensitive response characteristic to NO gas, and its response potential value increases with NO gas concentration. Elevating electrode sintering temperature can increase the size of NiO particles and shorten the length of the three-phase boundary (TPB) in the sensitive electrode. The average length of TPB is the longest in the sensitive electrode sintered at 1000 °C which corresponds to the best sensitive response to NO gas. The sensitive electrode's thickness also affects the NO response sensitivity, and the sensor with an electrode thickness of 14 μm has the most NO response sensitivity. In addition, the NO/NO2 gas mixture test results indicate that the current developed sensor is more sensitive to NO2 gas than that of NO gas.

ZrO2 and ZnO nanoparticles effect on setting time, microhardness, and compressive strength of calcium-enriched-mixture cement

Aim: Calcium-enriched mixture (CEM) cement is an endodontic biomaterial; however, enhancing its physical/mechanical properties remains a challenge. This in vitro study investigates the influence of zirconium oxide (ZrO2) and zinc oxide (ZnO) nanoparticles on the setting time, microhardness, and compressive strength of CEM cement. Methods: Four different groups of CEM cement were prepared: a control group without nanoparticles, two groups with ZrO2 or ZnO, and a group with a combination of nanoparticles. The nanoparticles were added to the powder in predetermined concentrations. The setting time was evaluated using the Gilmore needle method, while microhardness and compressive strength were determined using Vickers hardness and a universal testing machine, respectively. Results: The incorporation of ZnO slightly reduced the setting time, while the addition of ZrO2 significantly prolonged it compared to the control group. Interestingly, the combination of both nanoparticles exhibited a setting time comparable to that of the control group. Regarding the microhardness and compressive strength, both ZrO2 and ZnO significantly improved these properties compared to the control group. The combination of both nanoparticles showed the highest microhardness and compressive strength values among all groups. Conclusions: The addition of nanoparticles to CEM cement effectively modifies its physical and mechanical properties. The optimal combination of these nanoparticles can potentially achieve an improved balance between setting time and enhanced mechanical performance.

Enhancing the catalytic performance of Cu/ZnO/Al2O3 catalyst in methanol synthesis from biomass‐derived syngas with CeO2, MnO2 and ZrO2 as promoters

AbstractThe performance of Cu/ZnO/Al2O3 (CZA) catalysts promoted by addition of CeO2, MnO2 or ZrO2 in direct methanol production from unconventional syngas was experimentally investigated. The unconventional syngas used in this study contain 25% H2, 25% CO, 20% CH4, 20% CO2 and 10% N2, representing biomass‐derived syngas cultivated from an industrial wood chips pyrolysis plant. The catalysts were synthesised using co‐precipitation technique and tested for methanol synthesis in a fixed‐bed reactor. The activity test of the catalysts showed that the addition of CeO2 or ZrO2 to the CZA catalyst improved the methanol yield, albeit with lower selectivity, whereas adding MnO2 enhanced methanol selectivity but decreased the methanol yield. ZrO2‐promoted catalyst showed the best‐improved activity and stability. The calcined and spent catalysts were characterised using X‐ray diffraction (XRD), N2 physisorption, N2O chemisorption, hydrogen temperature‐programmed reduction (H2‐TPR) and X‐ray photoelectron spectroscopy (XPS). The characterisation results indicate that the catalytic activity is dependent on Cu dispersion, Cu‐active surface area, the catalyst reducibility, Brunauer–Emmett–Teller (BET) surface area and the Cu0/Cu+ ratio. In contrast, catalyst stability was related to the proportion of Cu+ among all surface Cu species.

RuNi/TiZr-MMO Catalysts Derived from Zr-Modified NiTi-LDH for CO-Selective Methanation.

CO-selective methanation (CO-SMET) is an efficient hydrogen-rich (H2-rich) gas purification technology for proton exchange membrane fuel cells. It is vital to develop suitable catalysts with good low-temperature activity for CO-SMET reactions. In this study, RuNi/TiZrx-mixed metal oxide (RuNi/TiZrx-MMO) catalysts with different molar ratios of Zr/Ti, derived from a Zr-promoted NiTi-layered double hydroxide (NiTi-LDH) precursor were successfully prepared using the co-precipitation and wet impregnation methods. The RuNi/TiZr0.2-MMO catalyst possesses higher catalytic performance in a lower temperature window of 180-280 °C, which can reduce the CO concentration to be below 10 ppm. The characterization results obtained from XRD, BET, SEM, TEM, XPS, TPR, and TPD suggest that the addition of ZrO2 increases the surface area of the catalyst, improves the dispersion of metallic nanoparticles, increases the reducibility of Ni species on the RuNi/TiZr0.2-MMO catalyst's surface, and enhances the adsorption and activation ability of CO, resulting in remarkable catalytic performance at lower reaction temperatures. Moreover, the RuNi/TiZr0.2-MMO catalyst demonstrated long-term catalytic stability and carbon resistance.