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

Abstract

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−PANI) for electrocatalytic reduction of Cr(VI). The reaction kinetics of the LGS− PANI 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 flowthrough 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−Cr(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 flowthrough mode, the LGS−PANI electrode reaches an average reduction efficiency of 99.

Emerging investigator series: carbon electrodes are effective for the detection and reduction of hexavalent chromium in water

“…Since this report, chromate detection and reduction has focused on complex methods requiring engineering of precious metal nano-particles and electrodes. 2,[13][14][15][16][17] We were intrigued by Compton's observations and sought to revisit and re-explore the behavior of chromate on carbon electrodes more in depth, over a wider range of conditions. Herein, a method is reported for the detection and reduction of CrIJVI) in water on inexpensive un-modified electrode substrate.…”

A review on application of graphene‐based microfluidics

“…The on‐chip pre‐concentration of the trace metal ions from a large‐volume sample followed by metal ion detection by the fluorescent GOQD sensor can provide an advanced platform for on‐site water pollution screening Ji. et al presented microfluidic flow through polyaniline supported by lamellar‐structured graphene for mass‐transfer‐enhanced electrocatalytic reduction of hexavalent chromium . Zhao et al presented microfluidics‐generated GO microspheres and their application to removal of perfluorooctane sulfonate from polluted water.…”

Corrugated stainless-steel mesh as a simple engineerable electrode module in bio-electrochemical system: Hydrodynamics and the effects on decolorization performance

“…As the mass transfer correlates to the reactions at the electrode surface, it may explain why, compared to the BES p-SMEM , the higher current, faster biofilm growth and shorter start-up duration were observed in the BES c -SMEM . A further study based on the computational fluid dynamics (CFD) analysis is warranted, which would help to reveal a clearer difference of the flow regime at these two types of electrode module [55].…”