A thin-film photocatalytic (PC) reactor with dual slant-placed electrodes was developed and successfully applied to degrade Carmine. In this PC reactor, both TiO2/Ti photoanode and cathode are slant-placed in reaction chamber, and aqueous thin-film formed on both anode and cathode as wastewater flowing through the electrode surface. Degradation efficiency can be enhanced 50% approximately due to additional degradation on the cathode. The mechanism of the dual slant-placed electrodes thin-film PC process was investigated. Self-generated electric field formed between the TiO2/Ti anode and Cu cathode based on the principle of establishing a Schottky barrier, which approved to be approximately 90 mV of potential and 8 mu A of current by measurement during 20 mg L-1 Carmine solution PC treatment. Under electric field, photo-generated electrons were transferred from anode to cathode. On the Cu cathode surface, the photoelectrons reacted either with dissolved oxygen (DO) to form H2O2, which then oxidized dye and resulted in indirect oxidation decolorization, or with dye to result in direct reduction decolorization. Wastewater flowing enhanced the mass transfer of target compound and kept the aqueous film fresh. The influence of cathode material was investigated and Cu proved to be the optimal material. (C) 2013 Elsevier B.V. All rights reserved.