Development of high ion-selective montmorillonite-incorporated polyethersulfone nanocomposite membranes for salinity gradient energy harvesting

Highly efficient ion-selective membranes hold promise for diverse applications, including energy harvesting. However, achieving optimal selectivity and cost-effectiveness remains a challenge hindering their commercialization. This study addresses these limitations by exploring a novel type of nanocomposite membrane, with a particular focus on developing sulfonated poly (ether sulfone) (SPES) nanocomposite membranes and investigating their cation selective properties, crucial for optimizing salinity gradient energy harvesting. In particular, montmorillonite (MMT) is incorporated into the membranes as an additive two-dimensional (2D) nanofiller. MMT allows not only to enhance the electrochemical properties of the ion exchange membrane, such as ion conductivity and permeability but also its physicochemical stability. Consequentially, the structural combination of SPES and MMT across nanocomposite membranes results in the formation of negatively charged confined fluidic channels, which enables highly cation-selective fluidic transport. Molecular dynamics simulations also elucidated mechanisms underlying the structural interaction between SPES and MMT. The nanocomposite membranes demonstrated a cation transference number of up to 0.97 and a conversion efficiency of 46.8 % under a 10-fold salinity gradient, exceeding the performance of reported 2D materials and other MMT-based nanocomposites. The developed membrane design offers a promising framework for a range of applications, including ion exchange, salinity gradient energy harvesting, and other nanofluidic processes.