Visible-driven Complex Oxides Photocatalysts with Nanostructure and Application on Environmental Remediation

Yongfa Zhu
Department of Chemistry, Tsinghua University, Beijing

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     Last modified: January 19, 2006

Abstract
In the past decades, photocatalytic degradation of harmful pollutants by the semiconductors has received considerable attention. Outstanding stability and oxidative power make TiO2 the best semiconductor photocatalyst for environmental remediation. Many persistent organic substances were degraded in TiO2 suspensions. Even so, slow reaction rates and poor solar efficiency (maximum 5%) have hindered the commercialization of this technology. Therefore, in an attempt to eliminate these drawbacks, many studies on modifying the surface or bulk properties of TiO2, including doping, co-deposition of metals, surface chelation, and mixing of two semiconductors, have been performed.
Nanostructured tungstate materials, such as ZnWO4, and Bi2WO6, have aroused much interest due to their unique combination of physical and chemical properties, in terms of molecular and electronic versatility, reactivity, and stability, it is reasonable to believe they may be a promising class of photocatalysts.
In our study, we have successfully synthesized Bi2WO6 nanosheets by simple hydrothermal process and a detailed growth mechanism of the Bi2WO6 nano-plates was also clarified. The photo-activities of the so-prepared samples for Rhodamine-B (RhB), 4-CP and formaldehyde photodegradation were systematically investigated. Bi2WO6 is a good photocatalyst for photodegradation of organic compounds under visible light irradiation. These results suggest the possibilities that some W-based photocatalysts with the activity for environmental applications may be developed. Besides, other nanostructured photocatalysts have also been studied in our work. These results showed that Ba5Ta4O15 nanosheets showed a higher photocatalytic activity for the degradation of pollutants compared with the bulk Ba5Ta4O15 samples under UV light. Bi2MoO6 nanosheet and ZnWO4 nanorod photocatalyst also show good photoactivies for degradation of organic pollution. The photodegradation mechanism of these new type photocatalysts is different from that of TiO2 photocatalysts.