Promoting Effects of In2O3 on Co3O4 for CO Oxidation: Tuning O2 Activation and CO Adsorption Strength Simultaneously

Vertically-aligned Co3O4 arrays on Ni foam as monolithic structured catalysts for CO oxidation: effects of morphological transformation

A generic hydrothermal synthesis route has been successfully designed and utilized to in situ grow highly ordered Co3O4 nanoarray (NA) precursors on Ni substrates, forming a series of Co3O4 nanoarray-based monolithic catalysts with subsequent calcination. The morphology evolution of Co3O4 nanostructures which depends upon the reaction time, with and without CTAB or NH4F is investigated in detail, which is used to further demonstrate the growth mechanism of Co3O4 nanoarrays with different morphologies. CO is chosen as a probe molecule to evaluate the catalytic performance over the synthesized Co-based oxide catalysts, and the effect of morphological transformation on the catalytic activity is further confirmed via using TEM, H2-TPR, XPS, Raman spectroscopy and in situ Raman spectroscopy. As a proof of concept application, core-shell Co3O4 NAs-8 presenting hierarchical nanosheets@nanoneedle arrays with a low density of nanoneedles exhibits the highest catalytic activity and long-term stability due to its low-temperature reducibility, the lattice distortion of the spinel structure and the abundance of surface-adsorbed oxygen (Oads). It is confirmed that CO oxidation on the surface of Co3O4 can proceed through the Langmuir-Hinshelwood mechanism via using in situ Raman spectroscopy. It is expected that the in situ synthesis of well-defined Co3O4 monolithic catalysts can be extended to the development of environmentally-friendly and highly active integral materials for practical industrial catalysis.

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.

Controlled synthesis of Pt and Co3O4 dual-functionalized In2O3 nanoassemblies for room temperature detection of carbon monoxide

Innovative Pt and Co₃O₄ nanostructure co-decorated In₂O₃ nanobundles have been successfully developed and demonstrated as high-performance room-temperature CO gas sensors.

The relationship between the chemical state of Pd species and the catalytic activity for methane combustion on Pd/CeO2

Three Pd/CeO₂ catalysts are synthesized by reduction-deposition and an impregnation method (IMP) to clarify how the chemical state of Pd influences the catalytic performance for CH₄ combustion.

The existing states of potassium species in K-doped Co3O4 catalysts and their influence on the activities for NO and soot oxidation

The fresh and washed K-doped Co₃O₄ catalysts were compared with pure Co₃O₄ in order to investigate the existing states of K species and their influence on the activities for NO and soot oxidation.

Enhanced CO oxidation on CeO2/Co3O4 nanojunctions derived from annealing of metal organic frameworks

The interface of nanojunctions plays an important role in the performance of heterogeneous catalysts. However, it is highly challenging to construct nanojunctions which are usually prepared by complex multistep processes. Metal-organic frameworks (MOFs), with designable metal centers and tunable organic ligands, are promising precursors for the one-step synthesis of nanojunctions. Herein, we prepared porous CeO₂/Co₃O₄ nanojunctions by direct annealing of MOFs in air. These unique nanojunctions exhibit remarkable catalytic activity for CO oxidation, which can achieve complete oxidization of CO to CO₂ at 110 °C. In contrast, the temperature required for 100% CO oxidation is 190 °C for pure Co₃O₄. Moreover, the nanojunctions can maintain complete CO conversion after 16 h at 110 °C. Density functional theory calculations revealed that the enhancement in the catalytic activity of CeO₂/Co₃O₄ nanojunctions can be attributed to the charge transfer through the interfaces of the nanojunctions.

NiMnO3/NiMn2O4 Oxides Synthesized via the Aid of Pollen: Ilmenite/Spinel Hybrid Nanoparticles for Highly Efficient Bifunctional Oxygen Electrocatalysis

This work develops the NiMnO₃/NiMn₂O₄ ilmenite/spinel hybrid oxides as highly efficient bifunctional catalysts toward both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). They are prepared with the aid of pollen, using a two-step annealing method. The interaction between NiMnO₃ and NiMn₂O₄ nanoparticles results in an enhanced charge transfer between nanoparticles and active species in electrolytes, which is favorable for their electrocatalytic activities. The surface oxidation states of Ni and Mn for the hybrid oxides can be tuned by pollen, which greatly influences the OER and ORR activities and the overall bifunctional activity. The surface Ni³⁺ facilitates OER activity, while the surface Mn³⁺ with a small amount of Mn⁴⁺ favors ORR processes. Through optimization, 0.61NiMnO₃/NiMn₂O₄ shows the highest OER activity, while 1.57NiMnO₃/NiMn₂O₄ can outperform the others in promoting ORR processes. Between them, 0.61NiMnO₃/NiMn₂O₄ exhibits the higher overall bifunctional activity. Furthermore, both of the optimized hybrid oxides show excellent durability during both OER and ORR processes. They can be considered as promising bifunctional catalysts for OER/ORR.

Multicomponent (Ce, Cu, Ni) oxides with cage and core-shell structures: tunable fabrication and enhanced CO oxidation activity

Solvothermal synthesis of Cu2O cubes from Cu(OAc)2 in ethanol provided templates for tunable formation of novel multicomponent composites: hollow CeO2-Cu2O (), core-shell NiO@Cu2O () and hollow CeO2-NiO-Cu2O (). Composites catalyze the oxidation of CO at a lower temperature than the parent Cu2O cubes.

Surface oxygen vacancies on Co3O4 mediated catalytic formaldehyde oxidation at room temperature

This study reveals the essential role played by surface oxygen vacancies in catalytic oxidation reactions, and complements the common viewpoint that Co³⁺ is the major activity species in Co₃O₄-based systems.

A simple grinding-calcination approach to prepare the Co3O4–In2O3 heterojunction structure with high-performance gas-sensing property toward ethanol

The development of gas sensing devices with high sensitivity, good selectivity and excellent stability is becoming increasingly important since toxic or harmful gases are a threat to human health.

Enhanced low temperature CO oxidation by pretreatment: specialty of the Au–Co3O4 oxide interfacial structures

The enhanced CO oxidation by Au deposition and particularly He- and in situ-pretreatments was elucidated in light of the structural specialties associated with the facets of Co₃O₄ substrates and the corresponding Au–Co₃O₄ interfaces.

Enhanced CO catalytic oxidation of flower-like Co3O4composed of small nanoparticles

The enhanced catalytic performance of flower-like Co₃O₄composed of nanoparticles originates from the redistribution of surface ions induced by the calcining process.