Abstract
Mesoporous transition metal oxides with high crystallinity and large pore volumes were successfully synthesized by a widely applicable ligand-assisted self-assembly approach. In this approach, a carboxyl-containing ligand is employed as a coordination agent to retard the hydrolysis and condensation rates of the precursors. The ligands interact with the PEO chains of P123 via hydrogen bonds, which cooperatively ensures the controllable co-assembly of template micelles and the metal source during solvent evaporation. The X-ray diffraction, transmission electron microscopy, and nitrogen sorption results show that the obtained mesoporous metal oxides are constructed from numerous highly crystalline nanoparticles and possess close-packed mesostructures with uniform pore size distributions. A series of mesoporous transition metal oxides (Co3O4, Mn2O3, Fe3O4, NiO, CuO, ZnO, and Cr2O3) and multi-metal oxide composite materials (Co3O4/Fe3O4, Co3O4/NiO, and Fe3O4/NiO) were successfully synthesized. By employing the crystalline Co3O4/Fe3O4 composites as electrocatalysts, high catalytic activity can be achieved during the oxygen evolution reaction. A low overpotential of 322 mV at a current density of 10 mA cm−2 is exhibited, which shows that this approach has great significance not only in synthesis but also in electrocatalysis.
Highlights
Mesoporous transition metal oxides possessing a large surface area and high degree of crystallization have attracted extensive attention because of their remarkable properties and promising applications in gas sensing, energy storage, catalysis, and photodetection[1,2,3,4,5,6,7,8]
Carboxylic acid-containing ligands can be used as structure-directing agents in soft-templating approaches[17,18], and the ligand-assisted evaporation-induced selfassembly (EISA) method developed by Deng and coauthors provides a new idea for the synthesis of stable and crystalline mesoporous oxides[19]
Great advances have been made in the synthesis of several mesoporous transition metal oxides, the development of a universal method to synthesize thermally stable and highly crystalline mesoporous metal oxides is still a great challenge
Summary
Mesoporous transition metal oxides possessing a large surface area and high degree of crystallization have attracted extensive attention because of their remarkable properties and promising applications in gas sensing, energy storage, catalysis, and photodetection[1,2,3,4,5,6,7,8]. One promising route is the hard template approach, which employs mesoporous silica or carbon as a rigid template to introduce the desired mesoporous structure and removes the template by etching or calcination to obtain mesoporous transition metal oxides[9,10,11,12]. This approach can synthesize unique crystalline and ordered mesoporous metal oxides but still has some deficiencies. Great advances have been made in the synthesis of several mesoporous transition metal oxides, the development of a universal method to synthesize thermally stable and highly crystalline mesoporous metal oxides is still a great challenge
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