Enhanced osmotic energy conversion through bacterial cellulose based double-network hydrogel with 3D interconnected nanochannels

Hydrogel with 3D networks have shown great potential for ion transportation and energy conversion. However, the micron size pores of hydrogel greatly limit the ion selectivity and energy conversion performance. Here, we report a bacterial cellulose (BC) derived hydrogel membrane with double-network (DN) and tailored ion transport channels by rationally filling acrylic acid (AAc)-co-acrylamide (AAm)-co-methyl methacrylate (MMA) polymers into BC hydrogel micropores. Fabricated AAM/BC DN hydrogel membrane displays a unique hierarchical interconnected porous structure and 3D cation transport channels. From the results, the maximum power density reached up to 7.63 W·m-2 at 50-fold salinity gradient under alkaline conditions (pH 11). Interestingly, the power density of 45.5 W·m-2 was achieved through acid-base neutralization reaction. Furthermore, hydrogel successfully obtained a power density of 28.4 W·m-2 from a mixed system of paper black liquor wastewater/seawater. The results of this investigation suggested the enormous potential of BC-based nanofluidic membrane in sustainable osmotic energy conversion.