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We investigated the effects of the heat-treatment atmosphere on the current generation of Ti electrodes in microbial fuel cells (MFCs). The maximum current density was achieved for TiO2 nanotube array electrodes heated in H-2 (TNA-H-2) (22.69 +/- 0.18 A m(-2)). Physical analysis of the Ti electrode surfaces revealed that the specific surface area increased after electrochemical anodization. The crystallinities of the TiO2 nanotube array electrodes heated in H-2 (81.66%), CH4 (74.48%), N-2 (59.67%), and O-2 (44.82%) showed a significant positive correlation with the corresponding current densities (P < 0.05, R-2 = 0.9469). In addition, the highest electron transfer rate constant was achieved for TNA-H-2 (2.38 s(-1)). The large specific surface area, good chemical stability, high electron transfer rate, and good biocompatibility of TNA-H-2 suggest its great potential for application as an anode system in MFCs. (C) 2017 Published by Elsevier Ltd.