Ultralow Frequency Electrochemical–Mechanical Strain Energy Harvester Using 2D Black Phosphorus Nanosheets

Advances in piezoelectric or triboelectric materials have enabled high-frequency platforms for mechanical energy harvesting (>10 Hz); however, virtually all human motions occur below 5 Hz and therefore limits application of these harvesting platforms to human motions. Here we demonstrate a device configuration based on sodiated black phosphorus nanosheets, or phosphorene, where mechanoelectrochemical stress–voltage coupling in this material is capable of efficient energy harvesting at frequencies as low as 0.01 Hz. The harvester is tested using both bending and pressing mechanical impulses with peak power delivery of ∼42 nW/cm2 and total harvested energy of 0.203 μJ/cm2 in the bending mode and ∼9 nW/cm2 and 0.792 μJ/cm2 in the pressing mode. Our work broadly demonstrates how 2D materials can be effectively leveraged as building blocks in strategies for efficient electrochemical strain energy harvesting.