Electrical Properties of Semiconductive α-Fe₂O₃ and Its Use as the Catalyst for Decomposition of Volatile Organic Compounds

Abstract

We are so far involved in the development of complete decomposition of organic wastes as well as volatile organic compounds (VOCs) by the use of thermally activated holes in titanium oxide (TiO₂) at high temperatures of about 350–500°C. In this study, we intend to replace TiO₂ with α-Fe₂O₃ (red hematite) in order to lower the operation temperature and also to electrically characterize α-Fe₂O₃ on the basis of the temperature dependence of electrical conductivity and Seebeck potential. Powdered α-Fe₂O₃ is found to exhibit a higher electrical conductivity at 500°C by three orders of magnitude as compared with that of room temperature. In addition, the Seebeck potential is negative in the temperature range between room temperature and 380°C, indicating that the dominant charge carriers are mostly holes. Our α-Fe₂O₃-coated catalyst-system exhibits equivalent or even better characteristics than that of TiO₂, although the specific surface of α-Fe₂O₃ (4.10 m²/g) is two orders of magnitude smaller than that of TiO₂ (298 m²/g).