Abstract
As a promising desalination technology, capacitive deionization (CDI) have shown practicality and cost-effectiveness in brackish water treatment. Developing more efficient electrode materials is the key to improving salt removal performance. This work reviewed current progress on electrode fabrication in application of CDI. Fundamental principal (e.g. EDL theory and adsorption isotherms) and process factors (e.g. pore distribution, potential, salt type and concentration) of CDI performance were presented first. It was then followed by in-depth discussion and comparison on properties and fabrication technique of different electrodes, including carbon aerogel, activated carbon, carbon nanotubes, graphene and ordered mesoporous carbon. Finally, polyaniline as conductive polymer and its potential application as CDI electrode-enhancing materials were also discussed.
Highlights
The concept of capacitive deionization (CDI) was first introduced in the 1960s in the University of Oklahoma by G.W
The first CDI system they designed was based on flew through mode in which electrode sheets were made of activated carbon powder and saline water was pumped through the charged electrode sheets
For titania-loaded Activated carbon powder (AC), the formation rate of electrical double layer in AC electrode was improved significantly and the amount of ions removed was increased by 62.7 %, along with good regeneration performance of electrode
Summary
The concept of capacitive deionization (CDI) was first introduced in the 1960s in the University of Oklahoma by G.W. Graphene as the novel material in CDI research showed good deionization performance than activated carbon powder, even with a much lower surface area. Graphene featuring three-dimensional structure as high performance CDI electrode using different templating methods was demonstrated due to higher surface area, pore volume and superior ion transportation pathway [89, 90]. Carbon black acted as cores to form core-shell structures with PANI shell covered uniformly on the surface in which carbon black was considered to be a good component to improve electrical conductivity of the electrode material efficiently. Incorporating with ordered macroporous carbon resulted in relatively lower specific surface, the PANI composite-based electrode showed high capacitance as good rate capability. Mesoporous carbon and PANI composites were synthesized though in situ chemical polymerization, the resultant materials were studied and reported to have higher specific capacitance and good reversibility. The graphene/CNT/PANI showed a super high cycling retention of 96 % after 5000 cycles [245]
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