Moisture-Enabled Electricity Generation from a Single-Layer Composite CNT-Polymer Membrane

Clean and renewable power sources are crucial toward the development of sustainable energy technologies, to address the global energy demand. Moisture-enabled electricity generators (MEGs) have emerged as promising candidates to harness ambient low-grade energy stored in the humidity of the atmosphere. In this study, single-layer composite membranes were developed, consisting of a hydrophilic cross-linked polymeric matrix of sodium poly(4-styrene sulfonate-co-glycidyl methacrylate) (P(SSNa-co-GMA)) and polyacrylic acid (PAA), and incorporating various types of carbon nanotubes (single-, double-, and multi-walled carbon nanotubes). These composite membranes can spontaneously absorb humidity and display mixed conductivity in a range of relative humidity (RH) environments. The combination of high swelling capacity, hydrophilic surface, and interconnected nanoscale pathways facilitates the formation of a strong ion concentration gradient under humid conditions, leading to higher and more stable voltage output. For example, MEGs based on MWCNTs reaches ∼0.65 V. These findings indicate the importance of fine-tuned morphology and nanotube dispersion in designing efficient MEG devices, as low-cost and self-sustaining energy systems.