(352e) Molecular Design of Redox-Interfaces: Selective Electrochemical Separations and Beyond

Su, X. - Presenter, Massachusetts Institute of Technology
Molecular level design is crucial for the development of new, more efficient electrochemical interfaces for a wide range of industrial and environmental applications. In particular, selective separations remain some of the most important processes in the chemical and biochemical industries, and are crucial for water purification and environmental remediation. Although there has been great interest in electrochemical systems for energy storage and electrocatalysis, they are still of limited use in the separations field due to a lack of molecular-selectivity, and high energetic costs. Here, I present my research in developing redox-active interfaces for selective electrochemical separations.

Redox-active species offer an attractive materials platform, especially organometallic compounds (metallopolymers and associated metal-organic complexes), due to fine control of electronic properties through chemical design. First, I discuss the engineering of specific Faradaic-driven interactions between our redox-centers and target compounds. We investigate the selective sorption and release of anions, cations, and even proteins, based solely on electrochemical control. In parallel, we unravel the intermolecular mechanisms through a combination of electronic structure calculations and spectroscopy, and show how molecular tuning can further enhance interactions, to address tough challenges such as fine chemical separations.

Second, we propose asymmetric Faradaic systems as a next generation configuration for electrochemical processes, since asymmetric systems show much higher current and energy efficiencies. We focus on counter-electrode design, in which the Faradaic process at the cathode operates in tandem with the equivalent process at the anode; ultimately enhancing ion-selective performance, lowering potential windows and preventing parasitic side-reactions. Finally, we explore the nano-scale film properties and physico-chemical behavior of our redox-films, and point to emerging directions beyond separations, especially novel materials design.

Fundamentally, the concepts explored have broad implications in electrochemical sensing, electrocatalysis and interfacial electrosorption. For chemical engineering, these findings demonstrate the capability of redox-based technologies for both environmental and chemical process separations, and eventually lead towards process intensification.