Negative space charge modulated ion transport through PEDOT:PSS hydrogels integrating nanofluidic channels for highly efficient osmotic energy harvesting

The exploitation of ion-selective membranes with high power density and low resistance is crucial for harvesting osmotic energy in natural environments. However, the exploration of membranes that synergistically satisfy the demands of these properties in osmotic energy conversion remains largely unresolved. Herein, we demonstrate the application of a negative surface-modified 3D porous poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hydrogel for osmotic membranes, which effectively improved their deficiencies. Experiments, validation and simulations confirmed that the hydrogel membranes have remarkable space charge-modulated ion transport properties. Consequently, an impressive power output of 6.26 W m-2 can be realized, which exceeds the prevailing commercial standard (5 W m-2). Meanwhile, five device units were connected in series to charge a supercapacitor which exhibited an impressive selectivity rate of 95.6%, coupled with an electrochemical energy conversion efficiency of approximately 45.8%. This research paves a new avenue towards the application of hydrogels in ultra-high performance osmotic membranes. The exploitation of ion-selective membranes with high power density and low resistance is crucial for harvesting osmotic energy in natural environments.