Reductive decolorization of azo dye in wastewater was investigated in a dual-chamber microbial fuel cell (MFC) equipped with cathodes made of graphite or rutile-coated graphite. Rapid reduction of methyl orange (MO) with concomitant electricity production was achieved when the rutile-coated cathode was irradiated by visible light. The electrochemical impedance spectra (EIS) indicate that the polarization resistance (R(p)) of the rutile-cathode MFC decreased from 1378 Omega in dark to 443.4 Omega in light, demonstrating that photocatalysis of rutile can enhance the cathodic electron transfer process. The combination of the biologically active anode and photocatalysis-supported cathodic reduction of MO obeyed the pseudo-first-order kinetics. The analysis of decolorization products indicates that the azo bond of MO was probably cleaved by photoelectrons at the irradiated rutile-cathode, resulting in the products of colorless hydrazine derivatives. In addition, concurrently enhanced electricity generation in the MFCs involving photocatalyzed cathodic reduction of MO was observed throughout this study. (c) 2009 Elsevier Ltd. All rights reserved.