Design of a Simple Carbon Nanotube‐Based Bilayer Membrane for Hydrovoltaic Power Generation

Water Evaporation‐Induced Electricity Generation (WEG), a green power generation technology, has made significant advances in recent years. Surface charge density, based on the electric double layer (EDL) theory, is critical for optimizing WEG performance. Herein, we report the fabrication of a carbon nanotube composite fiber paper via a simple dipping method. The carbon nanotubes (FMWCNT) densely anchored to the upper layer of filter paper significantly enhance the surface charge density of the capillary walls. The counterions in the EDL diffusion layer accumulate at both ends of the membrane under capillary flow, and, in conjunction with the high hydrophilicity of the filter paper, yield high voltage outputs. Depending on the FMWCNT loading, the bilayer membrane achieves a maximum open‐circuit voltage of 0.89 V, which is a record value compared with other paper‐based WEG devices. Multiple devices connected together generate sufficient power to continuously illuminate an LED. Moreover, our strategy of enhancing surface electrostatic charge to improve voltage output is applicable to various substrates, offering a simple and broadly applicable approach for developing high‐performance WEG devices.