Double-Network Ion Channels for High-Performance Osmotic Power Generation

Biomimetic nanochannels are desirable materials for high-efficiency utilization of osmotic energy. However, the current power generation performance is limited by the low ion selectivity and ion flux. Here, novel nanochannels with double-network structure based on cellulose nanofibers intercalated with carbon nanotubes are demonstrated. The relatively high cationic selectivity and ion flux are obtained due to the enlarged charge polarity and space for ion transport in the double-network nanochannel, which is favorable for the osmotic power conversion. To the best of the authors’ knowledge, the power density under 50-fold NaCl (4.67 W m⁻²) outperforms most state-of-the-art nanochannel membranes with the same test conditions. By applying the concentration gradient between artificial (50-fold KCl) and real seawater/river water, a high power density of 5.53 and 6.51 W m⁻² can be achieved respectively, which exceeds the standard output of the ion-selective membrane for commercialization. The design of the biomimetic double-network nanochannels provides a new platform for controllable ion transport and high-performance power generation.