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

Scavenging energy stored at the water/solid interface into electrical power by the natural water evaporation process provides a promising method to supply sustainable electricity for self-powered electronics. The main barriers constraining its applications are the limited materials availability and ambiguous underlying mechanisms, detrimental to the improvement of output power. Herein, we report a highly flexible and efficient evaporation-induced electricity generator (EIEG) that dexterously exploits the directional water capillary flow inside the silicon nanowires (SiNWs) mesh nanopores. Benefiting from the large surface/volume ratio and high surface potential of nanostructured SiNWs mesh film, an EIEG continuously delivers a high open-circuit voltage of ~1.5 V and a maximum power density of over 160 μW·cm−3, which surpasses the analogous flexible EIEGs. Moreover, the correlation between the output power and capillary flow direction, diffusion length, and velocity as well as the species and ionic strength of various liquids have been systematically explored to identify the mechanism underlying the power generation. This study not only provides an in-depth understanding of water/solid interactions but also spikes a green technique to fabricate flexible generators that tap energy from the copious water reservoir.