Mechanistic Studies of Chloro- and Nitrophenolic Degradation on Semiconductor Surfaces

This chapter attempts to elucidate the mechanistic details of chlorophenol and nitrophenol degradation on Titanium dioxide (TiO₂) by identifying charge-transfer species, short-lived transients, and longer-lived intermediates using a number of spectroscopic techniques. It presents the results of an in situ Fourier-transform infrared spectroscopy (FTIR) technique employed to probe the adsorption and photocatalytic degradation of 4-chlorophenol on TiO₂ particles in a gas-solid system. The chapter discusses the photodegradation of nitrophenols on a TiO₂ surface that is based on the principle of visible light sensitization by colored compounds. The findings of these two studies are significant in that they provide the fundamental basis for the development of efficient technologies to destroy hazardous chemicals. The photocatalytic degradation of a wide range of organic compounds using semiconductors such as TiO₂ and Zinc oxide has been reported in the literature. A novel use of diffuse reflectance FTIR spectroscopy has allowed us to study the photocatalytic transformation of4-chlorophenol adsorbed to the dry surface of TiO₂.