LEAPS-MPS: Electrochemical characterization of ion adsorption at solid-liquid interfaces

Grinnell College, Grinnell IA

Investigators

Abstract

In this project, funded by the MPS-LEAPS (Launching Early-Career Academic Pathways) Program and managed by the Division of Chemistry, Professor Molly M. MacInnes and her students at Grinnell College will perform studies focused on the development of methods to understand dissolved metal ion interactions with solid surfaces. Metal ions constitute a group of pollutants that are of great concern when they enter natural bodies of water. Understanding the interaction of these dissolved pollutants with solid surfaces not only informs our understanding of their transport and fate within the environment but also aids in the development of sorbent materials for removal of these ions from the environment. The solid surfaces of greatest interest are oxides, including silicon oxide (sand) and metal oxides. Current methods for probing reactions at oxide surfaces include methods that are expensive, difficult, or must be done in high vacuum environments. Professor MacInnes and her students will demonstrate the usefulness and simplicity of electrochemical techniques for probing surface reactions of metal ions on oxide materials in situ. Ultimately, this research could open the door to using electrochemical measurements as a way to probe the interactions of a wide variety of ions and molecules at solid surfaces. This research will be integrated with outreach activities, including a program called Market Science where students engage with community members in conversations about their research. Training will be developed to teach students about science communication, treating communication with a public audience as a two-way conversation and a way to learn about the community. Professor MacInnes and her students will demonstrate the effectiveness of using conductive metal oxides (FTO, ITO, and AZO) as electrodes for monitoring the adsorption and redox reactions of aqueous lanthanide and actinide ions on these metal oxide surfaces. Other surface-sensitive techniques, such as X-ray photoelectron spectroscopy and laser ablation ICP-MS will supplement the electrochemical experiments. Further, Professor MacInnes and her students will demonstrate the possibility of using electrochemistry to probe surface reactions on non-conductive materials. This will be done by using ultra-thin films of silica grown on metal electrodes as well as the native oxide layers on metal electrodes. Electrons can tunnel through films thinner than about 5 nm, allowing these non-conductive oxides to act as conductive materials. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.