Hard Templating Pathways for the Synthesis of Nanostructured Porous Co₃O₄

Abstract

The present study is concerned with the nanocasting preparation of Co3O4 nanostructures employing two-dimensional (2D) hexagonal SBA-15 and three-dimensional (3D) cubic KIT-6 as hard templates. The influence of framework connectivity of the parent silica and loading of the cobalt source are studied in detail. Structures can be tailored as isolated or randomly organized Co3O4 nanowires or as highly ordered mesoporous Co3O4 networks retaining the symmetry of the silica parent using 2D hexagonal parent materials. Applying cubic KIT-6 silica with suitable wall thickness and degree of framework interconnectivity as a template, we can vary the pore size of mesostructured Co3O4 from 3 nm up to values as high as 10 nm. To verify the influence of surface properties and texture, we employed different mesoporous silicas that were conventionally calcined at 550 °C and equivalent silica materials microwave treated in the presence of a concentrated H2O2/HNO3 mixture. The parent silica materials and the resulting Co3O4 were characterized in detail at different steps during the templating route by nitrogen physisorption measurements and powder X-ray diffraction. Transmission electron microscopy and scanning electron microscopy investigations were performed to visualize the structure and morphology of the nanocast materials, and thermogravimetry−differential thermal analyses (TG−DTA) were done to follow the formation of Co3O4. With our method, preparation of nanocast Co3O4 is highly reproducible, regardless of template shapes and sizes, which makes the pathway much more versatile for a great variety of templates.

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

“…[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. [26][27][28] In contrast, liquid-phase synthesis of Co 3 O 4 particles has been of signi cant interests because the liquid phase process has large potentials to obtain highly puri ed and homogenized Co 3 O 4 particles.…”

Nanocasting Synthesis of Mesostructured Co3O4 via a Supercritical CO2 Deposition Method and the Catalytic Performance for CO Oxidation

“…Nanocasting is a very effective method to produce mesoporous Co 3 O 4 , in which mesoporous silica or carbon serves as a hard template and its pores are infiltrated with precursors of Co 3 O 4 followed by calcination and removal of the hard template [17][18][19]. The key to the success of nanocasting is the complete filling of the mesopores because partial or insufficient loading of precursors inside mesopores is very likely to result in replicas with disordered pore structures.…”

Ordered mesoporous and bulk Co3O4 supported Pd catalysts for catalytic oxidation of o-xylene

“…3a) exhibited slightly distorted Type-IV isotherms in the relative pressure range of 0.4-0.8, reconfirming the formation of a mesoporous structure [15]. The capillary condensation steps of the Co 3 O 4 (3D) and Pd/Co 3 O 4 (3DL) are not pronounced, indicating the relatively small sizes of ordered domains [11]. From the data of pore size distributions (inset in Fig.…”

“…In recent years, ordered mesoporous transition metal oxides have received great attention owing to their uniform channel dimensions, open porous structure and multiple oxidation states [8][9][10][11][12][13]. Ordered mesoporous Co 3 O 4 was fabricated by some groups using different silica templates, such as KIT-5, SBA-15, SBA-16, KIT-6, and forming different replica mesoporous structures ((2d-hexagonal P6mm) (bicontinuous cubic Ia3d) (Im3n)) [11,[14][15][16][17][18].…”

“…Ordered mesoporous Co 3 O 4 was fabricated by some groups using different silica templates, such as KIT-5, SBA-15, SBA-16, KIT-6, and forming different replica mesoporous structures ((2d-hexagonal P6mm) (bicontinuous cubic Ia3d) (Im3n)) [11,[14][15][16][17][18]. It was shown that the three-dimensional cubic Ia3d mesoporous structure had a more open porous system than other mesostructures, facilitating the absorption and diffusion of the VOC molecules during the catalytic oxidation of short-chain VOCs [13,18,19].…”