Thin film composite on fluorinated thermally rearranged polymer nanofibrous membrane achieves power density of 87 W m-2 in pressure retarded osmosis, improving economics of osmotic heat engine

Membrane technology operating in highly concentrated solutions is essential in pressure retarded osmosis (PRO) applications to compete with other renewable energy technologies. Herein, we fabricated highly porous and robust electrospun membranes (ESMs) using a poly(benzoxazole-co-imide) (PBO) polymer. For the first time in osmotic-driven systems, novel one-step direct fluorination was adopted to increase hydrophilicity of the ESM. Direct fluorination increased the total surface energy of the ESM by boosting polar surface energy parameter, which eventually affected the formation of 'ridge & valley'-like thin film composite membrane (PBO-TFC-F5) through interfacial polymerization of the fluorinated ESM. As a result, PBO-TFC-F5 achieved an unprecedented power density of 87.2 W m(-2) using 3 M NaClaq as a draw solution at 27 bar. When PBO-TFC-F5 was used for osmotic heat engine (OHE), it showed a power generation cost of only 203 $center dot MWh(-1), which was less than half the cost observed using commercial membranes. This robust, porous, and high performance PBO-TFC-F5 opens up new possibilities in membrane-based power generation systems.