Induced Potential in Porous Carbon Films through Water Vapor Absorption

Abstract

Sustainable electrical potential of tens of millivolts can be induced by water vapor adsorption on a piece of porous carbon film that has two sides with different functional group contents. Integrated experiments, and Monte Carlo and ab initio molecular dynamics simulations reveal that the induced potential originates from the nonhomogeneous distribution of functional groups along the film, especially carboxy groups. Sufficient adsorbed water molecules in porous carbon facilitate the release of protons from the carboxy groups, resulting in a potential drop across the carbon film because of the concentration difference of the released free protons on the two sides. The potential utilization of such a phenomenon is also demonstrated by a self-powered humidity sensor.

Low‐Thermal‐Budget Doping of 2D Materials in Ambient Air Exemplified by Synthesis of Boron‐Doped Reduced Graphene Oxide

“…[ 44,45 ] Under highly humid conditions, water molecules are readily adsorbed on the B@rGO surface, facilitating the ionization of surface carboxyl groups to form COO – and H + . [ 46 ] The COO – groups act as hole traps, generally leading to hole depletion in p ‐type carbon materials, that is, to a baseline resistance increase. Another possible mechanism is the band gap increase due to the adsorption of water molecules on the grain boundary or defective sites of graphene flakes, which increases resistance.…”

Generating Electricity from Water through Carbon Nanomaterials

“…Unlike high humidity conditions, natural evaporation of water is am ore common water power source,a nd carbon black sheet was reported as ah ighly efficient water-evaporation-induced nanogenerator (Figure 6a). [28] Copyright 2016,Wiley-VCH. The carbonb lack sheet output an increasingo pen-circuit voltage of up to 1V when insertedi nto ab eaker with the bottom end covered by deionized water,a nd the output voltage couldb ew ell maintained for 8d ays (Figure 6b).…”

A Filter Paper‐Based Nanogenerator via Water‐Drop Flow

“…Then, the streaming voltage is generated when the dissolved ions compulsively flow with the direction of the surrounding solution. On the other hand, the difference in surface hydrophilicity and the ion gradient are obtained through hydrophilic treatment, [38][39][40] such as plasma processing or UV radiation. Xue et al [29] grew and annealed the modified carbon black onto a quartz substrate to induce electricity through water evaporation and capillary infiltrating.…”

“…[31,36] Wang et al [37] successfully harvested rain energy by the electrons-enriched poly(3,4-ethylenedioxythiophene) (PEDOT)graphene/PtCo monoelectrode with reasonable electrical signals and good durability. Liu et al [38] manipulated the porous carbon film with nonhomogeneous proton-donating and oxygen-containing functional groups to induce potential through water vapor absorption. On the other hand, the difference in surface hydrophilicity and the ion gradient are obtained through hydrophilic treatment, [38][39][40] such as plasma processing or UV radiation.…”