Co3O4/TiO2 heterostructures obtained by hybrid method

High surface-to-volume ratio Co3O4/TiO2 heterojunctions were fabricated by combining different methods. Atomic layer deposition (ALD) and a photochemical method were used to coat polystyrene (PS) 3D-Direct Opal (3D-DO) structures on conductive ITO substrates. Firstly, 3D-DO of PS were crystallized on ITO substrates to form the high surface-to-volume ratio template via a self-assembly method. A low-temperature ALD TiO2 film was infiltrated onto the PS opal structure. Then, the PS template was removed by a thermal treatment in air at 450 degrees C for 5 h. Hollow anatase phase nanospheres were obtained, crystallized in a face centered cubic (FCC) lattice with the (111) plane oriented parallel to the substrate surface. Finally, the hollow TiO2 nanospheres were coated with Co3O4 via a photochemical method. This ordered 3D nanostructure with designed morphology may find applications as surface-enhanced materials for photovoltaic devices. TiO2 hollow nanospheres obtained via low-pressure ALD (a) and Co3O4/TiO2 heterostructure (scanned region: 1.5 mu m) (b).