Effect of inorganic filler size on nanocomposite ion exchange membranes for salinity gradient power generation
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Reverse electrodialysis (RED) is a technique that can capture electrical potential from mixing two water streams of different salt concentration through permselective ion exchange membranes. Effective design of ion exchange membranes through structure optimization is critical to increase the feasibility of salinity gradient power production by RED. In this work, we present the preparation of organic-inorganic nanocomposite cation exchange membranes containing sulfonated polymer, poly (2,6-dimethyl-1,4-phenylene oxide), and sulfonated silica (SiO2-SO3H). The effect of silica filler size at various loading concentrations on membrane structures, electrochemical properties, and the RED power performance is investigated. The membranes containing bigger-sized fillers (70 nm) at 0.5 wt% SiO2-SO3H exhibited a relatively favorable electrochemical characteristic for power performance: an area resistance of 0.85 Ω cm2, which is around 9.3% lower than the resistance of the membranes with smaller filler particles. The power performance of this nanocomposite cation exchange membrane in a RED stack showed 10% higher power output compared with the membranes containing small particle size and achieved the highest gross power density of 1.3 W m-2. Thus, further optimized combination of material properties and membrane structure is a viable option for the development of effective ion exchange membrane design, which could provide desirable electrochemical performance and greater power production by RED.