Corrosion of Nanoscale Alloy Electrodes

Arizona State University, Scottsdale AZ

Investigators

Abstract

TECHNICAL SUMMARY: This research project examines alloy corrosion processes in nanoscale structures. The program involves a combined experimental and theoretical approach focused on developing broadly applicable thermodynamic models of dealloying corrosion. This problem is extraordinarily rich in that there are two intrinsic length scales that must be considered. One length scale is set by the alloy composition and the other is set by the physical dimensions of the sample. The richness of the problem derives from the interaction of these length scales, which leads to entirely new corrosion phenomena. Corrosion of such structures is important at monolayer levels and occurs at compositions which are not vulnerable to attack in corresponding larger macroscopic scale samples. Thus conventional approaches for characterizing dealloying corrosion are not applicable at the nanoscale. In order to perform this work we use a new technique for developing reproducible alloy nanoelectrodes in the size range of 3 ? 10 nm and employ a variety of characterization techniques including underpotential deposition for assaying surface compositions, electrochemical scanning tunneling microscopy and high resolution analytical transmission electron microscopy. The combination of experimental data generated on well characterized nanostructures together with our thermodynamic modeling will provide a general fundamental framework for understanding these important nanoscale corrosion processes. The science evolving from this research will impact diverse applications in nanotechnology. NON-TECHNICAL SUMMARY: This research examines corrosion of nanoscale structures such as those used as catalysts in fuel cells, nanoparticle based bio-assays, bio-sensing and environmental monitoring for security and surveillance. In the case of fuel cells for transportable power the stability of metal alloy catalyst particles to corrosion is the key problem and to date has limited this technology to widespread application. This program is evolving new experimental data and modeling that will provide engineering guidelines for the design of nanoscale structures that are stable to corrosion. In order to accomplish these goals students are trained to develop expertise in order to integrate knowledge in the disciplines of electrochemistry and materials science. Today there is a dearth of graduate students trained in the U.S. in this manner. Part of this problem stems from the perception students have that corrosion science is an old developed field and is separated from the current hot areas which include fields such as renewable energy and ?bio-nano?. This research program opens a new arena in corrosion science which should help to get more high quality students interested in corrosion. In support of this, we are developing new courses in materials electrochemistry which specifically focuses on the corrosion and electrochemical behavior of nanoelectrodes. This will be taught at the senior undergraduate/beginning graduate level and is aimed specifically at exciting student interest in this field. Both graduate and undergraduate students are involved in this research program. In addition to active involvement with the NSF funded Minority Graduate Education @ Mountain State Alliance (MGE@MSA) program, the PI is getting individuals from underrepresented groups involved in this research program.