The use of Ti 3 C 2 T x MXenes/polyaniline composite tremendously improved the electrokinetic energy conversion efficiencies of nano-hydroelectric generators, demonstrating a power output sufficient to charge a commercial battery for the very first time. 

Towards Watt-scale hydroelectric energy harvesting by Ti3C2Tx-based transpiration-driven electrokinetic power generators

Nano-hydroelectric technology utilizes hydraulic flow through electronically conducting nanomaterials to generate electricity in a simple, renewable, ubiquitous, and environmentally friendly manner. To date, several designs of nano-hydroelectric devices have been devised to maximize the electrokinetic interactions between water molecules and nanomaterials. However, the reported power generation of the state-of-the-art nano-hydroelectric generators is not sufficient for practical use, as tens of thousands of units were required to operate low-power electronics on a mW scale. Here, we utilize titanium carbide (Ti3C2Tx) MXene nanosheets, which have advantageous properties including metal-like conductivity and hydrophilicity, to facilitate the electrokinetic conversion of the transpiration–driven electrokinetic power generator (TEPG) with a remarkably improved energy generation efficiency compared to that of carbon-based TEPG. The Ti3C2Tx MXene-based TEPG delivered a high pseudo-streaming current of 120 μA by the fast capillary flow promoted by MXene sheets coated on cotton fabric. The strong cationic affinity of Ti3C2Tx enables the generator to achieve an output of 0.68 V and 2.73 mA when NaCl solution is applied. Moreover, incorporation of a conducting polymer (i.e., Ti3C2Tx/polyaniline composite) enhanced the ionic diffusivity while maintaining the electrical network of Ti3C2Tx. The optimized Ti3C2Tx/polyaniline composite TEPG generated a maximum voltage of 0.54 V, a current of 8.2 mA, and a specific power density of 30.9 mW cm−3, which was sufficient to successfully charge a commercial Li-ion battery as well as low-power electronics and devices with a volume of 6.72 cm3.

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Towards Watt-scale hydroelectric energy harvesting by Ti3C2Tx-based transpiration-driven electrokinetic power generators

Synergistic work of photo-thermoelectric and hydroelectric effects of hierarchical structure photo-thermoelectric textile for solar energy harvesting and solar steam generation simultaneously

Environment-adaptive power generation can play an important role in next-generation energy conversion. Herein, we propose a moisture adsorption-desorption power generator (MADG) based on porous ionizable assembly, which spontaneously adsorbs moisture at high RH and desorbs moisture at low RH, thus leading to cyclic electric output. A MADG unit can generate a high voltage of ~0.5 V and a current of 100 μA at 100% relative humidity (RH), delivers an electric output (~0.5 V and ~50 μA) at 15 ± 5% RH, and offers a maximum output power density approaching to 120 mW m-2. Such MADG devices could conduct enough power to illuminate a road lamp in outdoor application and directly drive electrochemical process. This work affords a closed-loop pathway for versatile moisture-based energy conversion. 

/pdf/moisture-adsorption-desorption-full-cycle-power-generation-1nec658c.pdf

Moisture adsorption-desorption full cycle power generation

https://www.nature.com/articles/s41467-022-30156-3.pdf

Direct electricity generation from water flow/evaporation, coined hydrovoltaic effect, has recently attracted intense interest as a facile approach to harvest green energy from ubiquitous capillary water flow or evaporation. However, the current hydrovoltaic device is inferior in output power efficiency compared to other renewable energy devices. Slow water evaporation rate and inefficient charge collection at device electrodes are two fundamental drawbacks limiting energy output efficiency. Here, we report a bioinspired hierarchical porous fabric electrode that enables high water evaporation rate, efficient charge collection, and rapid charge transport in nanostructured silicon-based hydrovoltaic devices. Such an electrode can efficiently collect charges generated in nanostructured silicon as well as induce a prompt water evaporation rate. At room temperature, the device can generate an open-circuit voltage (Voc) of 550 mV and a short-current density (Jsc) of 22 μA·cm-2. It can output a power density over 10 μW·cm-2, which is 3 orders of magnitude larger than all those reported for analogous hydrovoltaic devices. Our results could supply an effective strategy for the development of high-performance hydrovoltaic devices through optimizing electrode structures.

Bioinspired Hierarchical Nanofabric Electrode for Silicon Hydrovoltaic Device with Record Power Output.

Hydrovoltaic devices are proposed as an alternative way to directly generate electricity due to the ubiquity of water and its interaction with specific porous structures. At present, the output power density of the reported device is limited by its low current density arising from the low surface charge density and inferior charge transport capability of the active materials. In this work, an asymmetric structure consisting of positively charged conductive polyaniline (PANI) and negatively charged Ti3C2TX MXene is proposed to build a hydrovoltaic device to achieve high conductivity and surface charge density simultaneously. An extra polyvinyl alcohol layer is utilized between PANI and MXene to reserve the asymmetric structure and maintain a constant voltage output. As a result, a peak current density of 1.8 mA/cm2 is achieved, which is 18 times higher than the previous peak current density of the device with an inert electrode. Our work of incorporating an asymmetric structure provides an alternative way to target high-efficiency hydrovoltaic devices with a large current density.

Beibei Shao

Papers

Bioinspired Hierarchical Nanofabric Electrode for Silicon Hydrovoltaic Device with Record Power Output.

Asymmetric Charged Conductive Porous Films for Electricity Generation from Water Droplets via Capillary Infiltrating.

Freestanding Silicon Nanowires Mesh for Efficient Electricity Generation from Evaporation-Induced Water Capillary Flow

Electron-Selective Passivation Contacts for High-Efficiency Nanostructured Silicon Hydrovoltaic Devices

Integrating Hydrovoltaic Device with Triboelectric Nanogenerator to Achieve Simultaneous Energy Harvesting from Water Droplet and Vapor