Highly Efficient, Flexible and Self-Healable Moisture-Driven Energy Harvester based on 2D Vanadium Pentoxide Nanosheets

The ubiquitous source of atmospheric moisture brought about a fascinating research avenue of extracting atmospheric water to generate sustainable electricity. Energy may be extracted from ambient moisture with obvious and substantial advantages. This point-of-use technology provides a decentralized alternative to meet the energy needs in isolated off-grid places. Unlike traditional energy generators which predominantly rely upon fossil fuel, moisture-induced energy generators can extract energy from moisture in a sustainable and eco-friendly way. Herein, we demonstrated a self-healable moist electric generator (MEG) based on vanadium pentoxide (V₂O₅) 2D nanosheet membranes. Lamellar membranes of V₂O₅ nanosheets have been shown to be excellent cation conductors and excellent materials for harvesting energy from ambient moisture. Ultra-thin 2D nanosheets of V₂O₅was obtained by treatment of bulk V₂O₅crystals with hydrogen peroxide. V₂O₅ nanosheet membrane was fabricated by vacuum-assisted filtration of 2D V₂O₅ nanosheets dispersion over a PTFE support membrane. The V₂O₅ membrane was easily peeled off from the support membrane on drying to obtain a flexible and freestanding V₂O₅membrane. The V₂O₅ membrane consisting of percolated nanofluidic channels was sandwiched between a bottom solid copper foil and a perforated copper foil as the bottom electrode. The top electrode is perforated for exposure to atmospheric humidity. As the atmospheric water molecules come in contact with the V₂O₅ surface, an open-circuit voltage of 0.5 Volts and a short-circuit current of 0.3 microamperes is generated. The generated voltage and current is attributed to the preferential flow of cations through the V₂O₅nanochannels. The exposed surface and edges of V₂O₅ nanosheets have a high negative surface charge which results in the splitting of water molecules into H₃O⁺ and OH^- ions. An electrical double layer (EDL) is established at the V₂O₅/water interface which selectively permits H₃O⁺ ions through the channels. The mobile ions of the EDL transport through the nanofluidic channels creating a gradient between the two electrodes, resulting in a constant potential difference between the top and bottom electrodes which is harvested as electric current. The MEGs can be easily connected in parallel or series to enhance the current and voltage respectively. We demonstrate ten MEGs connected in series to power small electronic devices such as calculators and humidity meters. One of the key features of the V₂O₅ MEG is its ability to repair any physical damage to the active material owing to the water-assisted healing characteristics V₂O₅ membrane.