Facile Fabrication of Hierarchical Graded Structure to Maximize Photocatalytic Surface Area via Additive Manufacturing

TiO₂ hierarchical structure which has high surface area was demonstrated via additive manufacturing to maximize its exposed area from sunlight. Conventionally, structures are fabricated by electrospinning, hydrothermal and nanoparticle synthesis. Using these processes, complex shapes are not possible to make. In this study, we have adopted extrusion based additive manufacturing method which is one of the various additive manufacturing technologies to overcome existing problems to have no limitation in making complex shapes with great variety of materials. The hierarchical graded structure was fabricated by extrusion-based additive manufacturing machine using TiO₂ feedstock which is composed of Anatase-TiO₂ powder and polymeric binder system. Then, Hierarchical structure was debound and sintered to obtain porous ceramic structure. During sintering temperature ranging from 400 to 900 °C, anatase to rutile phase transformation occurs. Sintering conditions should be optimized to increase the weight percentage of anatase phase which shows much better photocatalytic efficiency than that of rutile phase. The amount of anatase phase tends to increase with deceasing sintering temperature. In order to find the optimized sintering temperature condition, the CO₂ selectivity based on CO₂ photoreduction result using each structure was measured and compared. Finally, it was confirmed that the extrusion-based additive manufacturing could be a potential fabrication route for photocatalytic application by making hierarchical structure with high surface area.