Light-Induced Enhancement of Osmotic Energy Conversion in Molybdenum Disulfide/Cotton Nanofiber Composite Membrane

Osmotic energy, a clean and renewable energy source, holds vast potential at the confluence of rivers and seas. 2D nanofluidic membranes offer a promising avenue for its efficient harvesting, yet their practical application is hampered by insufficient power density. Here we report a photoresponsive 2D nanofluidic membrane constructed by intercalating molybdenum disulfide with cotton nanofibers to form a stable composite structure. Under 50- and 500-fold salinity gradients, the membrane achieves power densities of 6.48 and 13.57 W m^{- 2}, respectively. By introducing asymmetric illumination on the low-concentration side, we create asymmetric temperature and charge gradients, which substantially enhance the osmotic energy conversion performance. Under a light intensity of 220 mW cm^{- 2}, the membrane achieves a power density of 9.93 W m^{- 2}, representing a 53% increase compared to non-illuminated conditions. This enhancement is accompanied by a 62% rise in the short-circuit current and an 8% increase in the open-circuit voltage. In tests using real seawater, the membrane delivers a power density of 6.06 W m^{- 2}, a 67% improvement over the non-illuminated condition. This study establishes a new strategy for highly efficient osmotic energy harvesting and demonstrates the potential of light-assisted osmotic energy conversion in practical marine environments.