We report the enhanced triboelectric energy harvesting efficiency in a polytetrafluoroethylene (PTFE)-aluminum (Al) based generator through a facile hydrothermal treatment of Al electrode. The dipping of the as-received Al into hot water for several hours results in an increase of surface roughness and electrical conductivity, probably due to the formation of a plate-patterned gamma-AlOOH on the Al surface. In a capacitor-type triboelectric generator, in which a PTFE plate vibrates in-between two Al electrodes, we observed that the triboelectric charge increases for the use of hydrothermally treated Al electrodes and reaches a maximum at a certain frequency. Considering the simple hydrothermal treatment of the electrode and the tuning of resonance-like frequency, the capacitor-type PTFE-Al triboelectric generator could be quite useful for a cost-effective, high efficient energy harvesting device for random mechanical vibrations in our daily life. (C) 2016 Elsevier B.V. All rights reserved.