Sulfonated Graphene as Cation‐Selective Coating: A New Strategy for High‐Performance Membrane Capacitive Deionization

Abstract

Membrane capacitive deionization (MCDI) featuring both high electrosorption capacity and high energy effi ciency holds promise for desalination. However, the large-scale applications of MCDI are limited greatly by the high cost of commercial ion-exchange membranes and the interfacial resistance. Here, a new strategy for high-performance MCDI is established using sulfonated graphene (SG) as cation-selective coating. A continuous ultrathin SG coating via self-assembly is formed and attached tightly onto the surface of electrospun carbon nanofi bers (CNFs) by a simple yet effective dip-coating technique, yielding SG-CNF composites with a hydrophilic surface, high electrochemical specifi c capacitance, and greatly reduced interfacial charge transfer rate. These result in signifi cantly enhanced capacitive deionization performance in terms of both electrosorption capacity and charge effi ciency. The SG coating shows excellent cation selectivity for an asymmetric cell with SG-CNFs as a cathode. The new approach may pave a way to novel micro-MCDI, i.e. novel applications of functional graphene-based materials for highperformance, energy-effi cient, and cost-effective desalination.Adv. Mater. Interfaces 2015, 2, 1500372 www.advmatinterfaces.de www.MaterialsViews.com Adv. Mater . Interfaces 2015, 2, 1500372 www.advmatinterfaces.de www.MaterialsViews.com Scheme 1. a) Schematic of the three-step synthesis of SG; insets display the digital images of rGO and SG suspension after standing for 1 week. b) Schematic of the "dip-coating" process; insets show the digital images of rGO-CNFs and SG-CNFs.

Ultrasound-assisted preparation of electrospun carbon fiber/graphene electrodes for capacitive deionization: Importance and unique role of electrical conductivity

“…thus, electrosorption capacity is increased or decreased. According to our published reports [49,50], the ACF-based electrode has more better cycling data. Therefore, in this research, we only use the data to calculate electrosorption from the 1st or 2st cycle.…”

Concentration‐Gradient Multichannel Flow‐Stream Membrane Capacitive Deionization Cell for High Desalination Capacity of Carbon Electrodes

“…[22] Instead of using film electrodes, flow electrodes (FCDI) [23][24][25] or af luidized bed [26] can also be used for CDI. [16,[27][28][29] Albeit significant advances through optimized operational parameters, [27] the operation of carbon electrodes at low salt concentration leads to ar educed specific capacitance (unit: Fg À1 carbon )a nd al imited salt-adsorption capacity (SAC;u nit: mg salt g À1 carbon ). At present, membrane CDI( MCDI) using ion-exchange membranes has become widely used in commercial systems.…”

“…In addition, the voltage of the cell can be reversed during the discharging step, which leads to as ignificantly enhanced CDI performance. [16,[27][28][29] Albeit significant advances through optimized operational parameters, [27] the operation of carbon electrodes at low salt concentration leads to ar educed specific capacitance (unit: Fg À1 carbon )a nd al imited salt-adsorption capacity (SAC;u nit: mg salt g À1 carbon ). Yet, al ow molar concentration,a st ypicalf or brackishw ater,i sn eededt oc apitalize on the energy efficiency of ion electrosorption in conventional CDI.…”

Ion-selective asymmetric carbon electrodes for enhanced capacitive deionization

“…However, the charge efficiency of most carbon electrodes in the CDI process is lower than 0.6, which is far less than 1 and limits its large-scale industrial application. 2,4,10 To promote the practical application of CDI technology, it is quite urgent to improve the charge efficiency and reducing energy consumption of the electrodes.…”