Investigation into the impact of CeO2 morphology regulation on the oxidation process of dichloromethane

Four distinct CeO2 catalysts featuring varied morphologies (nanorods, nanocubes, nanoparticles, and nano spindle-shaped) were synthesized through a hydrothermal process and subsequently employed in the oxidation of dichloromethane (DCM). The findings revealed that the nano spindle-shaped CeO2 exhibited exposure of crystal faces (111), demonstrating superior catalytic oxidation performance for DCM with a T90 of 337 °C and notably excellent low-temperature catalytic activity (T50 = 192 °C). The primary reaction products were identified as HCl and CO2. Through obvious characterizations, it showed that the excellent catalytic activity presented by CeO2-s catalyst might be related to the higher oxygen vacancy concentration, surface active oxygen content, and superior redox performance caused by specific exposed crystal planes. Meanwhile, CeO2-s catalyst owned outstanding stability, reusability, and water inactivation regeneration, which had tremendous potential in practical treatment.

Hydrothermal Synthesis of a Ce-Zr-Ti Mixed Oxide Catalyst with Enhanced Catalytic Performance for a NH3-SCR Reaction

A series of mesoporous CeZrTiO_x catalysts were prepared by a facile hydrothermal method. Compared with CeTiO_x catalysts synthesized under the same conditions, the catalytic activity and anti-SO₂ performance of the Ce1Zr1TiO_x catalyst are greatly improved, and at the gas hourly space velocity (GHSV) of 60 000 h^-1, the NO_x removal efficiency is maintained at 90% in the temperature range of 290-500 °C. The catalytic effect of ZrO₂ on the Ce-Ti catalyst NH₃-SCR activity was elucidated through a series of characterizations. The results revealed that the doping of Zr could significantly improve and optimize the structure of Ce-Ti catalysts. At the same time, due to the doping of Zr, the synergistic effect between Ce and Zr in the CeZrTiO_x catalyst can effectively increase oxygen mobility, total acid content, and surface adsorbed oxygen species and lead to a larger pore volume. In addition, the introduction of ZrO₂ made the transformation of Ce⁴⁺ into Ce³⁺ more obvious, and the 2Ce⁴⁺ + Zr²⁺ ↔ 2Ce³⁺ + Zr⁴⁺ reaction greatly improved the reducibility of Ce1Zr1TiO_x. Among them, the improvement of SCR performance and H₂O/SO₂ tolerance is due to the electronic interaction between Zr and Ce.

Simultaneous removal of gaseous CO and elemental mercury over Cu-Co modified activated coke at low temperature

Cu-Co multiple-oxides modified on HNO₃-pretreated activated coke (AC_N) were optimized for the simultaneous removal of gaseous CO and elemental mercury (Hg⁰) at low temperature (< 200 °C). It was found that 2%CuOx-10%CoOx/AC_N catalyst calcined at 400°C resulted in the coexistence of complex oxides including CuO, Cu₂O, Co₃O₄, Co₂O₃ and CoO phases, which might be good for the simultaneous catalytic oxidation of CO by Co-species and removal of Hg⁰ by Cu-species, benefiting from the synergistic catalysis during the electro-interaction between Co and Cu cations (CoO ⇌ Co₃O₄ and Cu₂O ⇌ CuO). The catalysis removal of CO oxidation was obviously depended on the reaction temperature obtaining 94.7% at 200 °C, while no obvious promoting effect on the Hg⁰ removal (68.3%-78.7%). These materials were very substitute for the removal of CO and Hg° from the flue gas with the conditions of 8-20 vol.% O₂ and flue-gas temperature below 200 °C. The removal of Hg° followed the combination processes of adsorption and catalytic oxidation reaction via Langmuir-Hinshelwood mechanism, while the catalysis of CO abided by the Mars-van Krevelen mechanism with lattice oxygen species.

Co-Supported CeO2Nanoparticles for CO Catalytic Oxidation: Effects of Different Synthesis Methods on Catalytic Performance

Hydrothermal and co-precipitation methods were studied as two different methods for the synthesis of CeO2nanocatalysts. Co/CeO2 catalysts supported by 2, 4, 6, or 8wt% Co were further synthesized through impregnation and the performance of the catalytic oxidation of CO has been investigated. The highest specific surface area and the best catalytic performance was obtained by the catalyst 4wt% Co/CeO2 with the CeO2 support synthesized by the hydrothermal method (4% Co/CeO2-h), which yielded 100% CO conversion at 130 °C. The formation of CeO2 nanoparticles was confirmed by TEM analysis. XRD and SEM-EDX mapping analyses indicated that CoOx is highly dispersed on the 4% Co/CeO2-h catalyst surface. H2-TPR and O2-TPD results showed that 4% Co/CeO2-h possesses the best redox properties and the highest amount of chemically adsorbed oxygen on its surface among all tested catalysts. Raman and XPS spectra showed strong interactions between highly dispersed Co2+ active sites and exposed Ce3+ on the surface of the CeO2 support, resulting in the formation of the strong redox cycle Ce4+ + Co2+↔ Ce3+ + Co3+.This may explain that 4% Co/CeO2-h exhibited the best catalytic activity among all tested catalysts.

Catalytic activity boost of CeO2/Co3O4 nanospheres derived from CeCo-glycolate via yolk–shell structural evolution

CeO₂/Co₃O₄ hybrid nanospheres have been successfully prepared via thermal decomposition of CeCo-glycolate precursors.

Oxygen Vacancy-rich Porous Co3O4 Nanosheets toward Boosted NO Reduction by CO and CO Oxidation: Insights into the Structure-Activity Relationship and Performance Enhancement Mechanism

Oxygen vacancy-rich porous Co₃O₄ nanosheets (OV-Co₃O₄) with diverse surface oxygen vacancy contents were synthesized via facile surface reduction and applied to NO reduction by CO and CO oxidation. The structure-activity relationship between surface oxygen vacancies and catalytic performance was systematically investigated. By combining Raman, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and O₂-temperature programmed desorption, it was found that the efficient surface reduction leads to the presence of more surface oxygen vacancies and thus distinctly enhance the surface oxygen amount and mobility of OV-Co₃O₄. The electron transfer towards Co sites was promoted by surface oxygen vacancies with higher content. Compared with the pristine porous Co₃O₄ nanosheets, the presence of more surface oxygen vacancies is beneficial for the catalytic performance enhancement for NO reduction by CO and CO oxidation. The OV-Co₃O₄ obtained in 0.05 mol L^-1 NaBH₄ solution (Co₃O₄-0.05) exhibited the best catalytic activity, achieving 100% NO conversion at 175 °C in NO reduction by CO and 100% CO conversion at 100 °C in CO oxidation, respectively. Co₃O₄-0.05 exhibited outstanding catalytic stability and resistance to high gas hour space velocity in both reactions. Combining in situ DRIFTS results, the enhanced performance of OV-Co₃O₄ for NO reduction by CO should be attributed to the promoted formation and transformation of dinitrosyl species and -NCO species at lower and higher temperatures. The enhanced performance of OV-Co₃O₄ for CO oxidation is due to the promotion of oxygen activation ability, surface oxygen mobility, as well as the enhanced CO₂ desorption ability. The results indicate that the direct regulation of surface oxygen vacancies could be an efficient way to evidently enhance the catalytic performance for NO reduction by CO and CO oxidation.

Hollow Mesoporous Co3 O4 -CeO2 Composite Nanotubes with Open Ends for Efficient Catalytic CO Oxidation

Catalytic performance is heavily dependent on how the structures of nanomaterials are designed. Co₃ O₄ -CeO₂ composite nanotubes with open ends and mesoporous structures were fabricated through a facile and environmentally friendly reaction. The mesoporous Co₃ O₄ nanotubes were synthesized by the calcination of cobalt-aspartic acid (Co-Asp) nanowires and coated with a CeO₂ shell. The composite nanotubes were characterized by SEM, TEM, XRD, and X-ray photoelectron spectroscopy. The composite materials comprise a combination of Co₃ O₄ nanotubes and CeO₂ nanoparticles with a hollow and mesoporous bimetallic oxide structure. The large BET surface area led to a higher degree of accessible active sites compared with other Co₃ O₄ -CeO₂ composite nanomaterials with other structures. The resulting Co₃ O₄ -CeO₂ -26.3 wt % composite nanotubes, with a CeO₂ content of approximately 26.3 wt %, achieved 100 % CO conversion at 145 °C. Additionally, the synergistic effect between the two metal oxides comprising the Co₃ O₄ -CeO₂ composite nanotubes was demonstrated by the enhanced catalytic activity compared with pure Co₃ O₄ nanotubes and CeO₂ nanoparticles.

Kinetic and Electrochemical Reaction Mechanism Investigations of Rodlike CoMoO4 Anode Material for Sodium-Ion Batteries

Sodium-ion batteries are considered the most promising power source for electrical energy storage systems because of the abundance of sodium and their significant cost advantages. However, high-performance electrode materials are required for their successful application. Herein, we report a monoclinic-type CoMoO₄ material which is synthesized by a simple solution method. An optimized calcination temperature with a high crystallinity and a rodlike morphology of the material are selected after analyzing the as-synthesized powder by temperature-dependent time-resolved X-ray diffraction. The CoMoO₄ rods exhibit initial discharge and charge capacities of 537 and 410 mA h g^-1, respectively, when used as an anode for sodium-ion batteries. The sodium diffusion coefficient in the bimetallic CoMoO₄ anode is measured using the galvanostatic intermittent titration technique and calculated in the range of 1.565 × 10^-15 to 4.447 × 10^-18 cm² s^-1 during the initial cycle. Further, the reaction mechanism is investigated using ex situ X-ray diffraction and X-ray absorption spectroscopy, and the obtained results suggest an amorphous-like structure and reduction/oxidation of Co and Mo during the sodium insertion/extraction process. Ex situ transmission electron microscopy and energy-dispersive spectroscopy images of the CoMoO₄ anode in fully discharged and recharged state reveal the rodlike morphology with homogenous element distribution.

A versatile CeO2/Co3O4 coated mesh for food wastewater treatment: Simultaneous oil removal and UV catalysis of food additives

Food waste water is one of the most urgent environmental problems for the close connection between food and our daily life. Herein, we use a simple hydrothermal method to prepare a highly efficient catalyst-CeO₂/Co₃O₄ compound on the stainless steel mesh, aiming for food waste water treatment. Possessing the superhydrophilic property and catalytic ability under ultraviolet light, CeO₂/Co₃O₄ coated mesh has successfully processed three representative contaminants in food wastewater, which are soybean oil (food oil), AR (food dye) and VA (food flavor) simultaneously with an one-step filtration. Besides, the mesh is stable in a wide pH range and performs well in reusability. Therefore, such a multifunctional material with simple preparation method, high processing efficiency and facile operation shows a promising prospect for practical production and application for food wastewater treatment.

Low-temperature CO oxidation over integrated penthorum chinense-like MnCo2O4 arrays anchored on three-dimensional Ni foam with enhanced moisture resistance

Advanced integrated nanoarray (NA) catalysts have been designed by growing metal-doped Co₃O₄ arrays on nickel foam with robust adhesion.

Strongly coupled CeO2/Co3O4/poly(3,4-ethylenedioxythiophene) nanofibers with enhanced nanozyme activity for highly sensitive colorimetric detection

In this work, we have prepared CeO₂/Co₃O₄ composite nanofibers via an electrospinning technique followed by a calcination process. Then core-shell structured CeO₂/Co₃O₄/poly(3,4-ethylenedioxythiophene) (PEDOT) composite nanofibers were fabricated through a redox reaction between the 3,4-ethylenedioxythiophene (EDOT) monomer and Co₃O₄ on the surface of CeO₂/Co₃O₄ composite nanofibers. The morphology and composition of the two composite nanofibers were confirmed by field-emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, and x-ray photoelectron spectra measurements. Due to the synergistic effect between CeO₂ and Co₃O₄, the catalytic activity was enhanced compared to that of independent oxide nanofibers. After the growth of PEDOT, the catalytic activity process was further improved, having achieved a secondary synergistic effect. Application of the two prepared composite nanofibers as peroxidase-like catalysts for the colorimetric detection of H₂O₂ was investigated. It is anticipated that this work can inspire researchers to develop various novel functional nanocomposites for applications in biosensing and environmental monitoring.

Low-temperature CO oxidation over CeO2 and CeO2@Co3O4 core–shell microspheres

The excellent CO catalytic activity and stability of CeO₂@Co₃O₄ composite were ascribed to the synergistic interactions between Co₃O₄ and CeO₂.