Exceptional capacitive deionization rate and capacity by block copolymer-based porous carbon fibers.

Liu, Tianyu; Serrano, Joel; Elliott, John; Yang, Xiaozhou; Cathcart, William; Wang, Zixuan; He, Zhen; Liu, Guoliang · Sci Adv · 2020

basic_science · Level V

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Abstract

Capacitive deionization (CDI) is energetically favorable for desalinating low-salinity water. The bottlenecks of current carbon-based CDI materials are their limited desalination capacities and time-consuming cycles, caused by insufficient ion-accessible surfaces and retarded electron/ion transport. Here, we demonstrate porous carbon fibers (PCFs) derived from microphase-separated poly(methyl methacrylate)-<i>block</i>-polyacrylonitrile (PMMA-<i>b</i>-PAN) as an effective CDI material. PCF has abundant and uniform mesopores that are interconnected with micropores. This hierarchical porous structure renders PCF a large ion-accessible surface area and a high desalination capacity. In addition, the continuous carbon fibers and interconnected porous network enable fast electron/ion transport, and hence a high desalination rate. PCF shows desalination capacity of 30 mg<sub>NaCl</sub> g<sup>-1</sup> <sub>PCF</sub> and maximal time-average desalination rate of 38.0 mg<sub>NaCl</sub> g<sup>-1</sup> <sub>PCF</sub> min<sup>-1</sup>, which are about 3 and 40 times, respectively, those of typical porous carbons. Our work underlines the promise of block copolymer-based PCF for mutually high-capacity and high-rate CDI.