Advanced integrated nanochannel membrane with oppositely-charged bacterial cellulose and functionalized polymer for efficient salinity gradient energy generation

Reverse electrodialysis (RED) systems employing charged nanochannels have gained prominence for harvesting salinity gradient energy. Nevertheless, fabricating nanochannel membranes with optimal ion selectivity and high energy conversion efficiency remains a significant challenge. In this study, we develop oppositely charged bacterial cellulose (BC)/polymer composite nano-channel membranes with precisely designed nanochannel architectures by integrating chemical modification with composite material technology. Initially, BC undergoes chemical modifications, including 2,2,6,6-Tetramethylpiperidine 1-oxy radical (TEMPO) oxidation and quaternisation. Subsequently, a polymer network is integrated into the modified BC network through a polymer synthesis technique. This approach successfully yields negatively charged BC/poly(sodium p-styrene sulfonate) (NBC/PSS) composite double-networked nanochannel membranes and positively charged BC/poly(dopamine) (PBC/PDA) composite double-networked nanochannel membranes. Notably, these membranes exhibit significantly enhanced ionic conductivities, with values of 0.0008 and 0.0014 S cm(-1) for the NBC/PSS and PBC/PDA composites, respectively, while also demonstrating superior ion selectivity with cation transfer numbers of 0.9 and 0.1 respectively. Furthermore, a series connection of 30 BCE/charged polymer-based RED devices successfully powers an electronic calculator. This work offers novel insights into the design of BC-based RED devices by integrating chemical modification and polymeric composite strategies for efficient salinity gradient energy generation.