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Morphological Control of Co3O4 and Its Photocatalytic Properties
Citation:
Kou, J. AND R. S. VARMA. Morphological Control of Co3O4 and Its Photocatalytic Properties. Presented at oral presentation at the Material Research Society 2011 ( MRS ) meeting, Boston, MA, November 28 - December 02, 2011.
Impact/Purpose:
To inform public
Description:
Cobaltosic oxide (Co3O4), a p-type semiconductor, belongs to the normal spinel crystal structure based on a cubic close packing array of oxide ions. The size, surface, geometry, and crystal phase of catalysts are important parameters for controlling their chemical, optical, and electrical properties. 3D hierarchical structure of Co3O4 was prepared using organics-free method. It was formed by hundreds of small nano platelets. Their diameters are about 100 nm, and the thicknesses are about 20 nm. They stacked to constitute the triangular prisms. To the best of our knowledge, the 3D triangular prism structure has not been described before. Co3O4 displayed high efficiency to catalyze isopropanol conversion even using common incandescent bulbs as light source. Exposed definite planes often affect the property of photocatalytic material. Co3O4 has two optical band gaps, 2.2 and 1.5 eV. The first band gap of Co3O4 can be associated to O2-→Co2+ charge-transfer process (basic optical band gap energy, or valence to conduction band excitation), while the second one to O2-→ Co3+ charge transfer (Co3+ level is located below the conduction band). The (001) and (111) planes contain only Co2+ cations, while the (110) plane is composed mainly of Co3+ cations. Size-controlled 2D hexagonal Co3O4 was prepared to systemically investigate the effect of exposed planes (111) on photocatalytic property. We observe that (111) exposed plane displays high photocatalytic activity.