Microfluidic Flow through Polyaniline Supported by Lamellar-Structured Graphene for Mass-Transfer-Enhanced Electrocatalytic Reduction of Hexavalent Chromium

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• 作者：Qinghua Ji ; Dawei Yu ; Gong Zhang ; Huachun Lan ; Huijuan Liu ; Jiuhui Qu
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：November 17, 2015
• 年：2015
• 卷：49
• 期：22
• 页码：13534-13541
• 全文大小：578K
• ISSN：1520-5851

文摘

Owing to its high efficiency and environmental compatibility, electroreduction holds great promise for the detoxification of aqueous Cr(VI). However, the typical electroreduction system often shows poor mass transfer, which results in slow reduction kinetics and hence higher energy consumption. Here, we demonstrate a flow-through electrode of polyaniline supported on lamellar-structured graphene (LGS鈥揚ANI) for electrocatalytic reduction of Cr(VI). The reaction kinetics of the LGS鈥揚ANI flow-through electrodes are 6.4 times (at acidic condition) and 17.3 times (at neutral condition) faster than traditional immersed parallel-plate electrodes. Computational fluid dynamics simulation suggests that the flow-through mode greatly enhances the mass transfer and that the nanoscale convection induced by the PANI nanodots increases the nanoscale mass transport in the interfacial region of the electrode/solution. In situ Raman spectroscopy shows that the PANI鈥揅r(VI) redox reactions are dominated by the leucoemeraldine/emeraldine transition at 1.5 V cell voltage, which also remarkably contributes to the fast reaction kinetics. Using single-pass flow-through mode, the LGS鈥揚ANI electrode reaches an average reduction efficiency of 99.8% with residual Cr(VI) concentration of 22.3 ppb (initial [Cr(VI)] = 10 ppm, flux = 20 L h^鈥? m^鈥?). A long-term stability test shows that the LGS鈥揚ANI maintains stable performance over 40 days of operation and achieves >98% reduction efficiency, with average current efficiency of as high as 99.1% (initial [Cr(VI)] = 10 ppm, flux = 50 L h^鈥? m^鈥?).