(713e) Understanding the Impact of Organometallic Redox Polymer Electrode Fabrication and Cycling Conditions on Stability and Selective Separation of Oxyanion Pollutants

Organometallic polymers that can undergo faradaic (redox) reactions have shown the ability to selectively and efficiently remove micropollutants with varying physico-chemical properties. However, these redox -electrodes degrade during long term cycling due to structural degradation, and subsequent ion channel collapse. To identify strategies that promote pollutant selectivity and redox polymer electrode longevity, various redox polymer electrodes were fabricated with chemical compositions, and operated across different operating potential windows while evaluating the selective removal of regulated pollutant oxyanions (Cr₂O₇^2- and HAsO₄^2-) commonly found in contaminated groundwater. Carbon paper substrates were modified by electrodepositing poly(vinylferrocene) (PVF), polypyrrole (PPy), and simultaneously PVF and PPy to form a hybrid PVF/PPy with specific capacitances of 31.0 F/g, 73.0 F/g, and 543.15 F/g respectively. Initial cycling performance of the polymers revealed rapid degradation of PPy and the Hybrid below 100 cycles and PVF after 500 cycles. Morphology of the electrodes were characterized by SEM, EDX, AFM, and XPS. Electrochemical modulation of batch and flow-cell gave insight into the relationship between coating morphology, selectivity, capacitance, and removal efficacy. A facile electrode pretreatment consisting of applying a negative potential for thirty minutes significantly improved the long-term cycling of the polymers to some of the highest values reported in literature, such as the case for PVF which maintained a capacitive retention of 100% for 6000 cycles. On the long-term, these efforts pave a pathway towards the feasible application of redox-polymers for advanced water purification systems in the real-world.