Porous cellulose membrane for salt differential gradient energy harvesting

Energy derived from the salinity gradient between seawater and river water is recognized as a sustainable energy source and an alternative solution for meeting the growing energy demand. The ion exchange membrane is essential for efficiently converting the salt differential gradient energy of the salinity gradient into electrical energy. Herein, we reported a sustainable, porous cellulose membrane (PCM) by a doping-removing strategy of polyvinyl pyrrolidone (PVP) during the fabricating process of the cellulose membrane. Such a strategy effectively optimizes the structure of cellulose membrane, such as improved porosity (from 66.2 to 89%), enlarged specific surface area (from 7.99 to 12.86 m²/g), and increased water retention value (from 113.4 to 141.1%). As a result, the developed PCM shows excellent ion transport capacity and selectivity with a high t₊ of 0.88. The power density of PCM reaches up to 4.16 W/m², substantially exceeding that of the primary cellulose membrane. Moreover, the PCM harvests salt differential gradient energy very well with long-term stability, over 80,000 s with continuous operation. The PCM, utilizing sustainable and low-cost natural materials, shows considerable promise for renewable salt differential gradient energy harvesting.