Mesoporous Co₃O₄ with Controlled Porosity: Inverse Micelle Synthesis and High-Performance Catalytic CO Oxidation at −60 °C

Abstract

Crystalline mesoporous cobalt oxides with improved catalytic activity in CO oxidation were synthesized using an inverse surfactant micelle method. The prepared materials are monodispersed nanoparticle aggregates, and the mesopores are formed by connected intraparticle voids. Powder X-ray diffraction (PXRD), N2 sorption, field emission scanning electron microscope (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) revealed that both pore and nanoparticle sizes are enlarged with increasing thermal treatment temperatures (150–450 °C). Mesoporous cobalt oxide calcined at 350 °C exhibited the best oxidation activity and can achieve complete oxidization (100% conversion) of CO to CO2 at −60 °C under normal conditions (∼3–10 ppm of H2O) and at 80 °C under moisture rich conditions (∼3% H2O). The commercial Co3O4 reached 100% conversion at 220 °C under normal conditions. X-ray photoelectron spectroscopy (XPS), O2-temperature-programmed desorption (O2-TPD), H2-temperature-programmed reduction (H2-TPR), CO-TPD, and N2 sorption analyses indicated that the surface oxygen vacancy and large surface area promoted the lattice oxygen mobility of the catalysts and further enhanced their catalytic performance. The catalysts were deactivated by accumulation of water and formation of carbonates, but their activities can be easily restored by expelling water and carbonates at moderate temperature (200 °C).

Direct Hydrothermal Synthesis of Size-Controlled Co₃O₄ Nanocubes under Highly Condensed Conditions

“…1 (c) and (d)) into account, the particles with a hexagonal thin platelet shape and a cubic shape, seen in Fig. 2 (c) [6][7][8][9][10]13,14) The present observed in situ oxidation by nitrate ions might become an efcient procedure to obtain further mixed valence functional metal oxide nanoparticles in one-pot process.…”

“…[1][2][3][4][5] Especially, tricobalt tetraoxide (Co 3 O 4 ), a mixed-valence transition metal oxide with spinel crystal structure, is regarded as one of the most promising p-type semiconducting materials for industrial and scienti c applications such as heterogeneous catalysts, [6][7][8][9][10][11][12] solid-state sensors, [13][14][15] magnetic materials, 16,17) and lithium ion rechargeable batteries. [18][19][20][21] Up to date, various types of preparation methods have been developed for the preparation of Co 3 O 4 by thermal decomposition, [6][7][8]20,22,23) chemical spray pyrolysis, 24) spattering, 25) and sol-gel process.…”

“…The resulting Co 3 O 4 particles controlled in their size, crystalline diameter, and morphology have been expected to exhibit unique material features. 8,9,[13][14][15][16] In this regard, extensive efforts have been carried out to obtain Co 3 O 4 ne particles with various shapes. For example, Xie et al reported that nanorod-shaped Co 3 O 4 particles, obtained by way of calcination of solvothermally prepared cobalt hydroxide carbonate, show low-temperature CO oxidation property.…”

Fabrication of mesoporous Co3O4 oxides by acid treatment and their catalytic performances for toluene oxidation

“…Alternatively, various transition metal oxides have been extensively studied over the past several years as oxidation catalysts because of their advantages including a lower price and adequate catalytic activities at relatively low temperature [3][4][5][6][7][8][9][10]. Among these metal oxides, Co 3 O 4 has attracted much attention due to its excellent catalytic performance in numerous reactions, e.g., the catalytic oxidation of CO, NO or VOCs as well as soot combustion [11][12][13][14][15][16][17][18].…”

Surface plasmon-driven catalytic reactions on a patterned Co3O4/Au inverse catalyst

“…34 It was found that a small Co 3 O 4 -SiO 2 nanocomposite catalyst prepared using an activated carbon template exhibits very high activity for CO oxidation at À76 C.…”