Water-Evaporation-Induced Electric Generator Built from Carbonized Electrospun Polyacrylonitrile Nanofiber Mats

Electricity has been generated from evaporation-driven water flow in films of carbon soot particles and other porous media. This paper reports the placement of carbon nanofiber mats (CNMs) on fiberglass screens for the construction of efficient water-evaporation-induced generators (WEIGs). These CNMs are prepared from carbonizing electrospun polyacrylonitrile nanofiber mats and then treating them with oxygen plasma. After electrode attachment to the two ends of a CNM, one electrode is immersed into water. Water rises in the mat due to capillary action and evaporates from the mat surface due to thermal energy provided by the environment. The steady rise of water pushes the dissociated ions of the surface functionalities upward, resulting in a streaming current and an electric potential. This paper investigates how the generated short-circuit current, I_s, and open-circuit voltage, V_o, of the WEIG change with structural parameters of the CNMs. Under optimized conditions, these CNMs produce electricity at an areal power density of 83 nW/cm², which is almost 10 times those offered by some existing ones. Thus, the easy-to-handle CNMs are an attractive porous scaffold for WEIGs.