Dependence of photoelectric behavior of TiO2 electrodes on processing variables

The photoelectrochemical conversion behavior of TiO2 ceramic electrodes has been investigated as a function of electrode processing variables such as Al2O3 dopant, surface roughness, and grain size. The photocurrent increased with Al2O3 dopant up to 0.1 and 0.05 wt. % in the specimens reduced at 700 and 800 °C, respectively, and then decreased. However, the photoresponse appeared around 415 nm, which very closely corresponded to the energy band gap of TiO2(∼3.0 eV), regardless of reduction temperature and the amount of Al2O3. These results suggest a bulk excitation process involving dopant and a defect-related state in the gap of the TiO2 semiconductor. The photocurrent increased with increasing surface roughness and grain size in the undoped TiO2 ceramic electrode behavior due to adsorption and/or reflection of light and the grain-boundary effect.