Engineered Sulfonated Polyether Sulfone Nanochannel Membranes for Salinity Gradient Power Generation

Ion conduction in nanoscale ion channels or ion pumps to produce electrical signals is the basis of many fundamental biological processes. Inspired by biological ion channels, artificial nanochannels have been extensively explored to mimic the regulation of ion transport in nanochannels and to be applied in salinity gradient power generation. In this study, sulfonated polyether sulfone (SPES) membranes with many nanochannels were constructed via a phase separation method and applied in the salinity gradient power generation field. The nanochannel structure (nanochannel size and length) in the membrane was adjusted by controlling the SPES content and the thickness of the casting solution. These SPES membranes exhibited typical surface charge governing ion transport and excellent cation selectivity. The numerical simulation of ion transport properties for nanochannels with a series of nanochannel sizes and lengths was performed to analyze the effect of the nanochannel structure on the ion transport and salinity gradient power generation properties. The calculated results show that the nanochannels with length and size satisfying a certain relation possess optimal salinity gradient power generation properties. These SPES membranes were also used to generate electricity by mixing artificial seawater (0.5 M NaCl) and river water (0.01 M NaCl). The output power densities of the SPES membranes (M30–10 and M30–50) with the optimized nanochannel structure reached up to 5.8 and 5.6 W m–2, respectively.