Improving Electrosorption Performance in Membrane Assisted Capacitive Deionization Cells Using Asymmetric Electrodes Configuration
During MCDI operation, electrode polarization results in the attraction of counter- ions (opposite in polarity to the charged surface), while co-ions (similar in polarity to the charged surface) are repelled away from the polarized surface . The membranes used for the operation hinder the repulsion of co-ions back into the bulk, leading to an increased flux of counter-ions to balance the co-ions contained in the macropore space resulting in typically higher charge efficiencies over the CDI only system. In a departure from the traditional architecture which utilizes the same electrodes to form both the anode and cathode, MCDI systems can instead be asymmetrically assembled with ion-specific electrodes to increase specific charge excesses, and whereby any such specificity can be quantified via potential of zero charge (PZC) measurements.
In order to demonstrate benefits to deionization performance, we will present the electrosorption performance and charging characteristics of MCDI cells configured with pristine and nitric acid-treated Zorflex activated carbon electrodes with PZCs of -0.2 and 0.2 V vs SCE, respectively, based on differential capacitance measurements. Results from the asymmetric configuration will be compared to those from pristine anode-pristine cathode configurations to quantify the extent of variation in performance.
The authors are grateful to the U.S. - China Clean Energy Research Center, U.S. Department of Energy for project funding (No. DE-PI0000017), and thankful for the support of the State of Wyoming Advanced Conversion Technologies Task Force for their support.
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