(125b) Molecular Design of Electroactive Redox-Interfaces for Integrating Separations and Reactions

Separation processes play a critical role in water purification, materials recycling, carbon dioxide mitigation, and advanced chemical and biomolecular manufacturing. Thermal and pressure-based separation methods can often incur high energetic costs, while conventional adsorption technologies require harmful solvents and regenerants. Electrochemical separations offer a sustainable alternative, by regulating kinetics and thermodynamics based solely on electrical control. Selective electrosorption can be reversible without any extra chemical input, leading to modular and sustainable operations, and potentially even coupled with renewable energy.

Redox-active interfaces offer an attractive platform for performing selective electrochemical separations. In particular, electroactive polymers offer a wealth in flexibility in terms of functional group design, and control of electronic properties. First, we discuss the design of electrochemically-driven binding interactions in metallopolymers for selective anion capture [1-2]. Second, the capabilities of redox-electrodes are leveraged towards not only selective capture, but tandem environmental transformation of contaminants and heavy metal pollutants, within a single device. By judicious electrochemical engineering and asymmetric design, electrosorbents and electrocatalysts can be configured to enable reactive separation within the same device, towards contaminants of concern such as heavy metals and perfluoroalkyl substances (PFAS) [3,4]. Finally, we present new electrochemical approaches for critical metal recovery and waste recycling, through structural control and tunability of charge-transfer interactions [5].

From a fundamental perspective, these concepts point towards emerging directions in electrochemical interface design – by superimposing properly tuned chemical interactions, we can reach beyond double-layer effects and achieve unprecedented molecular selectivity. We envision redox-systems to also play a role in integrating reaction and separations, and assist in the development of new technologies for electrochemical process intensification.

References

[1] X. Su, et al. “Electrochemically-mediated selective capture of heavy metal oxyanions chromium and arsenic from water,” Nature Communications, 2018, 9, 4701.

[2] X. Su, et al, “Asymmetric Faradaic systems for selective electrochemical separations,” Energy & Environmental Science, 2017, 10, 1272-1283.

[3] K. Kim, S. Cotty, J. Elbert, R. Chen, C.H. Hou, X. Su, “Asymmetric Redox-Polymer Interfaces for Electrochemical Reactive Separations: Synergistic Capture and Conversion of Arsenic”, Advanced Materials, 2020, 32(6), 1906877.

[4] K. Kim, P. Baldaguez Medina; J. Elbert, E. Kayiwa, R. Cusick, Y.J. Men, X. Su, “Molecular tuning of redox-copolymers for selective electrochemical remediation.” Advanced Functional Materials, 2020, 30(52), 2004635.

[5] R. Chen, X. Su et al., “Structure and Potential-Dependent Selectivity in Redox-Metallopolymers: Electrochemically-mediated Multicomponent Metal Separations”, Advanced Functional Materials, 2021, 31(15), 2009307.