Electromechanical and Electrochemical Energy Harvesting from Ambient Moisture

Considering that over 75% of carbon emissions arise from electricity generation using fossil fuels, an emerging concept for achieving carbon neutrality involves the development of eco-friendly “self-powering” devices. These devices would be able to harness energy from various renewable sources, including but not limited to photovoltaics, thermoelectrics, piezoelectrics, and triboelectrics, rather than relying solely on the grid for power. However, electricity generation from renewable resources has often been limited by unstable outputs or specific requirements for a working environment. Notable efforts have been devoted to revisiting water energy as water is one of the most abundant and ubiquitous renewable sources covering more than 70% of the earth’s surface. For example, the ocean is expected to produce more than 32,000 TWh of energy every year, which is three orders of magnitude higher than global energy consumption. Further, the annual atmospheric moisture energy has been estimated to total over 0.5 TW assuming that 5.05 X 10⁵ km³ of water precipitation in the atmosphere can be fully converted into electrical energy, but moisture energy harvesting has been receiving less attention due to the lack of mature technologies. Triboelectric nanogenerators (TENGs) are emerging as an electromechanical energy conversion technology due to their light weight, simple fabrication, diversity in material selection, and high energy conversion efficiency, but the power output of TENGs needs to be trimmed to stably power the electronics. Concomitantly, the development of nanotechnology has allowed the harvesting of moisture energy using moisture-activated electricity generators (MEGs) in which asymmetric hydration of ions within an electrolyte promotes spontaneous ion diffusion, resulting in electricity generation through the external circuit. In this talk, I will address several strategies for power management of TENGs and MEGs to achieve high-performing self-powered electronics, including current manipulation and instric signal rectification.