| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2018) | |
| Nanomaterials | Monday Sessions |
| Session NM-MoE |
| Session: | NanoCatalysis |
| Presenter: | Anna Patricia Cristobal, University of the Philippines |
| Authors: | A.P. Cristobal, University of the Philippines M.G.K. Ramos, University of the Philippines A.D. Montallana, University of the Philippines L.B. Zhang, National Taiwan University of Science and Technology, Taiwan, Republic of China J.P. Chu, National Taiwan University of Science and Technology, Taiwan, Republic of China M.R. Vasquez, University of the Philippines |
| Correspondent: | Click to Email |
Designing multiphase or multicomponent semiconductor heterojunctions is a promising strategy to enhance the performance of photocatalytic materials. Titanium dioxide (TiO2) is a material of interest as a photocatalytic material because of its availability, stability, and cost-effectiveness. However, one major drawback of TiO2 is its wide band gap resulting to photocatalytic activity in the UV region only. Through heterojunction coupling of TiO2 with a lower band gap semiconductor such as cuprous oxide (Cu2O) with a direct band gap of 2.17 eV, visible light active photocatalytic activity can be achieved. TiO2/Cu2O heterojunction thin films were assembled in a configuration wherein the junction of the coupled semiconductors is exposed to light irradiation for photocatalysis. This design ensures that photocatalytic reaction can occur in both semiconductors since they are exposed to the light source. A layer of TiO2 thin film was deposited on (100) silicon (Si) substrate via reactive RF magnetron sputtering coupled with post deposition thermal annealing at 500°C. To form the heterojunction, ordered Cu clusters were patterned on top of the TiO2 layer through a mask. The deposited Cu were transformed into Cu2O by thermal oxidation at 200°C in air atmosphere followed by slow cooling at a rate of 0.48°C/min. The TiO2/Cu2O heterojunction films were characterized using XRD and FE-SEM with EDS mapping. Photocatalytic performance was evaluated by visible light photodegradation of methylene blue dye as the test analyte. The XRD pattern of the TiO2/Cu2O heterojunction film indicated the existence of rutile and anatase phases of TiO2 as well as the existence of mostly Cu2O phase. SEM image of the TiO2/Cu2O showed a patterned thin film design composed of a TiO2 thin film layer decorated with grain-like Cu2O clusters that are approximately 500 μm in diameter. At higher magnification, the TiO2 thin film exhibited a porous columnar structure while the Cu2O is characterized by terraced grain-like structures. Using an effective thin film surface area of 1.0 cm x 2.5 cm, around 50% removal rate of methylene blue was observed in 6 h of visible light irradiation. This promising approach of designing immobilized heterojunction thin films offers a potential for wastewater treatment applications using visible light irradiation.