Thermally Activated Cr2O3+x for Elimination of Volatile Organic Compounds

We have previously shown that oxide semiconductors (for example, TiO2, NiO, etc.) exhibit significant catalytic effects when heated at about 350-500 degrees C. This is due to the formation of a vast number of highly oxidative holes at high temperatures. Then, we applied the present finding for complete removal of volatile organic compounds (VOCs). In the present investigation, we focused on Cr2O3+x (0 < x < 1) in an attempt to lower the operation temperature of VOC decomposition. We present here how the low-temperature operation proceeds with Cr2O3+x and also elucidate why Cr2O3+x is colored green, on the basis of the temperature dependences of electrical conductivity and Seebeck potential of Cr2O3+x. The green color of Cr2O3+x is found to arise from Cr vacancies in Cr2O3+x and the vacancies are responsible for the formation of a narrow conduction band or a deep acceptor level, resulting in the low-temperature operation of VOC decomposition. [doi:10.2320/matertrans.M2010085]