Low-Friction Graphene Oxide-Based Ion Selective Membrane for High-Efficiency Osmotic Energy Harvesting

Graphene-based laminate membranes with selective ion-transport capability show great potential in renewable osmotic energy harvesting. One of the great challenges is to reduce the overall energy barriers while remain the high ion selectivity in the transmembrane ion transport process. Here, a strategy is proposed to break the trade-off between ion selectivity and permeability in laminar nanochannels using amphiphilic molecules as modifier, which enhances the surface charge density of nanochannel by loading more ion polymer with polar head and lows the frictional force of ion transport with hydrophobic tail. The conversion efficiency can reach to 32% in osmotic energy harvesting (0.5 m/0.01 m concentration gradient) after adopting this modifier. During the process of mixing real river water and seawater, the maximum power density can reach to 13.38 W m-2. The amphiphilic molecules also bind adjacent nanosheets, endowing the membrane's strong mechanical strength and high stability in aqueous solution. This work can open up a new way to regulate the transmembrane ion transport in 2D laminate membranes. Amphiphilic molecule and ion polymer are used to enhance the ion selectivity and permeability of graphene oxide-based laminar membrane for osmotic energy conversion. The ionic polymer polyacrylate sodium (PAAS) provides negatively charged groups to the nanochannel. The amphiphilic molecule dimethyldioctadecylammonium bromide (DODAB) can absorb more PAAS molecules to enhance the ion selectivity and formhydrophobic interface in the nanochannel to reduce the friction of ion transport.image

Automated summary

This study proposes a strategy to enhance the ion selectivity and permeability of graphene oxide-based laminar membranes using amphiphilic molecules as modifiers, achieving high conversion efficiency and power density in osmotic energy harvesting.