Geometric Tuning for Enhanced Moisture-Driven Electricity Generation Enabled by Graphene-Oxide Flakes

Abstract

In this work, we formulate water-based graphene oxide (GO) inks to fabricate moisture energy generators (MEGs) while a two-fold geometric tuning is proposed to encourage enhanced performance. Two GO-based structures with distinctly different thicknesses were prepared as the moisture absorbing layer: a GO-pellet (GOP) and a thinner GO-film (GOF). The effect of electrical contacts’ configuration on the MEG’s output voltage (Vo) was evaluated as a second geometric tunning approach by varying the surface area of the contacts and their orientation with respect to the GO plane, i.e., horizontal or vertical. GOF-based devices that employed a horizontal contacts’ configuration demonstrated champion Vo values (~350 mV) and the fastest response to humidity (3 min required to reach maximum Vo when the relative humidity, or RH, was increased). In GOP devices with horizontal point-like contacts, Vo is inversely related to the contacts’ distance, with a maximum Vo of ~205 mV achieved at a ~1 mm contacts’ distance. GOP-based MEGs with point-like contacts placed vertically to the GO-plane yielded a higher Vo value (~285 mV), while the humidity response time was 15 min. Replacing these contacts with large area electrodes in GOP devices resulted in devices with a slower response to humidity (~30 min) due to a smaller exposed GO surface area. These geometric tuning techniques allowed for the investigation of the optimum device configuration towards efficient moisture-based energy generation with a fast response.

Implementation of Cyclical Processes in the Moisture Electricity Generation for Continuous Operation

“…If we recall, this is reminiscent of the development of solar cells after the discovery of the gate photoelectric effect in Schottky contacts based on metallic copper and copper oxide (Cu-Cu 2 O), which were unclaimed for some time due to very low efficiency. However, materials that can be used to create moisture electric generators are currently being actively studied, they are protein nanowires , [6,9] carbon nanoparticles, [6,10,11] graphene, [6,12,13] oxide nanomaterials (TiO 2 , ZnO, Al 2 O 3 , CaSiO 3 ) [6,14] and others. [10][11][12][13][14][15][16] Among them, a special place is occupied by studies of oxide porous materials, [2,7,[10][11][12][13]17,18] on the surface of which a potential difference appears due to moisture adsorption, i.e., moisture electric generators.…”

“…However, materials that can be used to create moisture electric generators are currently being actively studied, they are protein nanowires , [6,9] carbon nanoparticles, [6,10,11] graphene, [6,12,13] oxide nanomaterials (TiO 2 , ZnO, Al 2 O 3 , CaSiO 3 ) [6,14] and others. [10][11][12][13][14][15][16] Among them, a special place is occupied by studies of oxide porous materials, [2,7,[10][11][12][13]17,18] on the surface of which a potential difference appears due to moisture adsorption, i.e., moisture electric generators.…”

“…Due to the large number of processes occurring in structures, on the surface of which a potential difference appears when saturated with moisture or dehydration, various authors have different interpretations of the reasons for changes in the potential difference on the surface of these structures . [11,12] At the same time, a deeper understanding of the mechanisms responsible for the appearance of potential differences in these structures in the presence of a humidity gradient in them, that will make it possible to increase the specific power and efficiency of such moisture electric generators. To understand these mechanisms, it may be useful to involve the concepts used in the physics of semiconductor devices to the processes occurring in such structures in the presence of a humidity gradient, as was done in.…”