Synthesis of Single‐Component Metal Oxides with Controllable Multi‐Shelled Structure and their Morphology‐Related Applications

Abstract

Multi‐shelled hollow spheres metal oxides, namely materials with more than three shells, have attracted increasing attention due to their unique structure. The preparation methods of typical metal oxides including NiO, Co3O4 and ZnO etc. have been summarized in this review. Simultaneously, the parameters that influence the ultimate morphologies, shell number as well as the compositions have also been discussed. The potential application fields in energy conversion and storage, electromagnetic wave absorption, photocatalysis that related to the unique structure are also highlighted. Finally, the future researches of multi‐shelled hollow spheres metal oxides are further discussed.

Rational Construction of Hierarchically Porous Fe–Co/N-Doped Carbon/rGO Composites for Broadband Microwave Absorption

“…According to the microwave absorption mechanism, when absorbers have magnetic loss, dielectric loss, and impedance match, more microwaves can enter the interior of the materials and be converted into other forms of energy and dissipated [8,9]. In past decades, many efforts were devoted to researching composites for enhancing microwave absorption, such as (Fe, Ni, Co)/C [10][11][12], (Fe, Ni, Co)/rGO [13][14][15], MFe 2 O 4 /rGO (M = Fe, Ni, Co) [16][17][18][19], MFe 2 O 4 / CNTs [20][21][22], and NiO/SiO 2 /Fe 3 O 4 /rGO [23,24]. However, these materials have the shortcoming of narrow absorption bands, which seriously hinders their practical applications.…”

Nanocomposite‐based inorganic‐organocatalyst Cu(II) complex and SiO2‐ and Fe3O4 nanoparticles as low‐cost and efficient catalysts for aniline and 2‐aminopyridine oxidation

“…Fe 3 O 4 nanoparticles with high surface area, dipole–dipole attraction capability, less toxicity, inexpensive preparation procedures, and superparamagnetic features [ 12,13 ] have been reported to be the most successful support for the organic [ 14,15 ] and inorganic catalysts (e.g., SiO 2 , ZnO, NiO, TiO 2 ) [ 16 ] by improving their chemical stability and reactivity. [ 17 ] In addition, the Brunauer–Emmett–Teller (BET) surface area of Fe 3 O 4 nanoparticles could be measured when it is coated with SiO 2 or TiO 2 species.…”

“…[ 15 ] Furthermore, SiO 2 could strongly support within the pendant functional groups in the organic and inorganic frameworks. [ 14,15 ] Consequently, the heterogeneous inorganic‐organocatalysts are immobilized on the highly functionalized Fe 3 O 4 nanoparticles coated with the active silica species. Considerably, the central metal ions (M n + ) of the inorganic‐organocatalyst occupies the active sites on the surface of the active SiO 2 @Fe 3 O 4 with high dispersion, more stability, and higher reactivity.…”

“…Considerably, the central metal ions (M n + ) of the inorganic‐organocatalyst occupies the active sites on the surface of the active SiO 2 @Fe 3 O 4 with high dispersion, more stability, and higher reactivity. [ 14 ] The presence of Fe 3 O 4 promotes the interaction of the inorganic‐organocatalyst with the active SiO 2 because of its strong magnetic features. [ 21,22 ] Recently, research studies focused on the synthesis of new and highly magnetic transition metal oxides covered by a shell of SiO 2 and supported an inorganic‐organocatalyst to be used as a heterogeneous catalyst.…”

“…In particular, due to the low cost of Cu 2+ reagents, high reactivity as eco‐friendly catalysts for many catalytic‐applicable systems, high coordination behavior, and stability of low valent Cu 2+ , Cu 2+ complexes were used as homogeneous and heterogeneous catalysts (by supporting metal‐oxide nanoparticles) in myriad catalytic reactions. [ 11–20,22,26,27 ]…”