A general ligand-assisted self-assembly approach to crystalline mesoporous metal oxides

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.