Room-temperature Synthesis and Oxygen-reduction Catalytic Performance of Hollow ZnMn2O4 Nanospheres and Nanocubes

This paper reported the room-temperature synthesis of ZnMn2O4 spinels. The formation of hollow ZnMn2O4 with nanospheres and nanocubes structures was accomplished by reduction of amorphous MnO2 precursors using NaBH4 in aqueous solution containing Zn2+. The structure, morphology, composition and surface properties of the as-prepared products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and brunauer-emmett-teller (BET) measurements. It is found that the sizes of as-prepared hollow ZnMn2O4 nanospheres and nanocubes are about 400-700 nm with wall thickness of 40 nm, and that the walls of the hollow ZnMn2O4 nanostructures are densely aggregated by tiny particles with diameter of 5-7 nm. Furthermore, the activities of oxygen reduction reaction (ORR) in alkaline media of the as-prepared hollow ZnMn2O4 nanospheres and nanocubes were also investigated. The experimental results show that the hollow ZnMn2O4 nanospheres exhibit better electrocatalysis performance with a high current density and an electron transferred number of 3. 5, indicating their promising application as low-cost catalysts for ORR.