Voltage Distribution in Porous Carbon Black Films Induced by Water Evaporation

Abstract

Water-evaporation-induced (WEI) electricity generation has been widely studied, but the explanation for the working mechanism remains controversial yet. In this study, porous carbon black (CB) films with multiple parallel electrodes were prepared and the voltage distribution in these films was investigated during WEI electricity generation. We found that in both toluene and ethanol CB films, voltage between neighboring electrodes increases first but then decreases with increasing height above the bulk water surface. This voltage distribution derives from similar volumetric flow rate distribution of water inside the film, which is caused by the hydrophilicity of film and water evaporation. Our results support streaming potential and present more details during WEI electricity generation. It is helpful for understanding the mechanism in other material systems as well.

Water‐Enabled Electricity Generation: A Perspective

“…A summary of the output characteristics of some of these devices under standard operating conditions is shown in Figure . Because carbon‐based materials have a high conversion efficiency, they account for the majority of the active materials used in water‐enabled electricity generation systems, with the focus being on graphene‐based materials, [ 15,22,24,36–39,44–46,48,55,66,68–81 ] CNPs and carbon nanofibers (CNFs), [ 13,14,16,25,53,64,67,82–91 ] polymers, [ 23,31,38,66,83,89,92–99 ] and biomaterials. [ 26,30,69,74,90,91,100–102 ] Solid oxide materials [ 10,12,13,19,20,54,64,103–106 ] are also favored as they are easily fabricated into an active layer and are stable even in harsh environments.…”

“…a) Distribution of materials used in applications. [ 10,12–16,19,20,22–27,30,31,33–40,44–48,53–55,64–80,82–108,117–123 ] b) Output voltage and power density for different materials. c) The output voltage and d) averaged voltage of single and integrated devices.…”

“…Nanomaterials including 0D nanoparticles, 1D nanowires, 2D thin films and 3D foams, with a high surface area to volume ratio and extensive reaction sites, are ideal as the active medium in water-enabled electricity generators. As a result, many functional materials including carbon-based materials, [23,38,67] solid oxides, [10,12,13] biomaterials, [26] and composite systems [13,38,66] have been used in WEEGs in order to improve output performance. A summary of the output characteristics of some of these devices under standard operating conditions is shown in Figure 7.…”

“…A summary of the output characteristics of some of these devices under standard operating conditions is shown in Figure 7. Because carbon-based materials have a high conversion efficiency, they account for the majority of the active materials used in water-enabled electricity generation systems, with the focus being on graphene-based materials, [15,22,24,[36][37][38][39][44][45][46]48,55,66,[68][69][70][71][72][73][74][75][76][77][78][79][80][81] CNPs and carbon nanofibers (CNFs), [13,14,16,25,53,64,67,[82][83][84][85][86][87][88][89][90][91] polymers, [23,31,38,…”

“…water-enabled electrical generators. [109] In this context, GQDs, [73] GOs, [38,45,46,48,55,66,69] CNPs, [16,25,67] carbon nanotubes, [87,88] various types of polymers (poly(4-styrensulfonic acid)-PSSA, PAAS, poly(vinyl alcohol)-PVA) [38,94] and biomaterials (protein nanowires, natural wood, paper) [26,30,101] have been evaluated for applications in WEEGs. A primary advantage of these materials is that they are strongly hydrophilic, which facilitates the absorption of water molecules from moisture or liquid water.…”