Wiley interscience angewandte chemie international edition

You can find it, as well as forthcoming Reviews, Highlights, and Essays, at www. Fischer, H. Drexler, A. Spannenberg, B. Sundermann, C. As long as there is no page number available these articles should be cited in the following manner: Author s , Angew. Cornils Highlights Mesoporous Composites G. Angewandte Chemie International Edition — Wiley. Continue with Facebook. Sign up with Google. Log in with Microsoft. The design is both simple and has favorable attributes, including: 1 a high rate of capillary flow due to high porosity and 2 stability against degradation under working conditions.

Experimental Section. MilliQ water was used for all hydrovoltaic measurements. A typical device fabrication process is illustrated in Figures 2 and S1. All hydrovoltaic measurements were carried out using a Metrohm potentiostat.

Copper tape was used as a counter and working electrode, and MilliQ water was used as a solvent. First, the open circuit voltage was measured to determine the open circuit potential OCP from various devices.

Furthermore, linear sweep voltammetry LSV was then used to measure the short circuit current I sc , and cyclic voltammetry was used to study the non-faradic behavior of the electrodes. Furthermore, OCP and LSV were measured at different load resistances to estimate the maximum power output of the device. Results and Discussion.

Importantly, repeated LSV measurements show consistent voltages and currents, indicating no measurable changes to structural integrity or surface reactivity of these devices, Figure 3 a. Furthermore, to confirm that the power generation is solely due to capillary and evaporation phenomena rather than chemical reactions of copper electrodes, V oc was measured using an inert graphite electrode, which produced a similar voltage to those of copper electrodes, Figure S3.

Table 1. To further evaluate the all-weather compatibility and to determine the optimal conditions for the device, performance was evaluated in a humidity-controlled chamber.

This demonstrates that providing a porous support, such as a TLC plate in this case, assists in sustaining the water flow even at higher humidity, carrying charges through the main substrate and generating a streaming potential.

It was found that the electrode arrangement used see Figure 1 was necessary for observing the hydrovoltaic phenomenon; consistent with a streaming potential being the major mechanism of charge generation. When a glass plate with two electrodes was partially submerged in water or is measured with no water, there was no measurable output potential or current, indicating that both Al 2 O 3 and water are necessary for electricity generation.

Also, when the copper electrodes were pasted parallel to the flow direction of water, that is, vertically, the device showed a negligible power output.

A potential difference was only observed between the bottom and top of the device when placed half-submerged in water, supporting an electrokinetic phenomenon, where electric double layer formation occurs at the heterogeneous interface between the solid surface and water.

The EDL formation arises from solvation of water molecules under the electric field of the polarized solid surface. Anions are attracted, while the cations are repelled, resulting in distribution of charges near the solid surface and formation of an EDL. The repelled positive ions concentrate in water, while hydroxyl anions move with the water and are collected at the top electrode. From this movement of charges, a streaming potential voltage is generated.

We denote the V oc sign of this direction as positive, as shown in Figure 1. To explore the ionic strength effect on HV performance, the device performance was measured at different ionic concentrations.

As shown in Figure 5 , V oc is inversely dependent on the NaCl concentration in a range of 10 —2 to 10 —1 M. This concentration dependency is a further confirmation of a streaming potential driven by the electrokinetic effect.

Higher salt concentrations were not used as corrosion of the copper electrodes becomes significant over the timescale of these experiments. The spacing between the top and bottom electrodes was varied from 2 to 7 cm while keeping the width constant at 2 cm.

Both V oc and I sc increased when the spacing between the electrodes was increased from 2 to 4 cm. This increase is possibly due to the faster evaporation rate when the water travels to a higher capillary height, resulting in a higher accumulation of charge carriers. Figure 6 a shows the output voltage and current dependence on load resistance. The power output can be simply amplified by either series or parallel combinations of different devices.

Recently published articles on evaporation-driven electricity generation mechanisms focussed on favorable conditions for power generation, such as a high wind speed and a high temperature, but did not provide detailed results at different humidity levels.

Supporting Information. Author Information. The authors declare no competing financial interest. Emerging hydrovoltaic technology. Nature Research. Water contains tremendous energy in a variety of forms, but very little of this energy has yet been harnessed. Nanostructured materials can generate electricity on interaction with water, a phenomenon that we term the hydrovoltaic effect, which potentially extends the tech. In this Review, starting by describing fundamental properties of water and of water-solid interfaces, we discuss key aspects pertaining to water-carbon interactions and basic mechanisms of harvesting water energy with nanostructured materials.

We further discuss potential device applications of hydrovoltaic technologies, analyze main challenges in improving the energy conversion efficiency and scaling up the output power, and suggest prospects for developments of the emerging technol.

Green Energy Environ. Water-evaporation-induced electricity with nanostructured carbon materials. Nature Publishing Group. Water evapn. It has previously been utilized in a no. Here, we show that water evapn. We find that evapn.

The interaction between the water mols. This approach to electricity generation is related to the traditional streaming potential, which relies on driving ionic solns. Generating Electricity from Water through Carbon Nanomaterials. A review. Over the past ten years, electricity generation from water in carbon-based materials has aroused increasing interest. Water-induced mech. In this Concept article, we focus on the basic principles of elec. The current challenges and potential applications of power conversion with carbon nanomaterials are finally highlighted.

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