LAUSR

This study reports a concept of a water/moisture-induced hygroelectric generator based on the direct contact between magnesium (Mg) alloy and oxidized carbon nanofibers (CNF). This device generates an open-circuit voltage up to 2.65 V within only 10 ms when the unit is placed in contact with liquid water, which is higher than the reduction potential of magnesium. The average peak short-circuit current density is ~ 6 mA/cm2, which is among the highest values yet reported for water-induced electricity generators. Our results indicate that the galvanic corrosion occurs at the interface between the CNF and Mg electrode, but that the device can still generate electricity because of the high contact resistance caused by the work function difference between Mg and CNF and the surface oxidation. The oxidized CNF is shown to absorb water/moisture and get reduced, leading to a capacitive discharging effect to provide enhanced signal amplitude and sensitivity. These devices are found to be highly sensitive to small quantities of water, and their high output voltage and current makes them useful for the detection of water vapor in the human breath as well as for changes in ambient humidity. Mg/CNF systems then provide a new technology for use in the fabrication of self-powered water/moisture sensors and in the development of portable electric power generators.