Molecular catalysts such as nickel cyclam and rhenium bipyridine have been widely studied for CO2 reduction reaction, which has a great potential to store renewable energy as fuels. Self-assembled monolayers (SAMs) on gold, mostly consisting of alkanethiols, are gaining considerable interest in the field of electroanalysis due to its ability of making organized and functionalized surfaces. However, SAMs on gold cannot stay stable at potentials as negative as it’s needed for electrolytic CO2 reduction reaction (usu. &lt;= 1.5V vs. Ag/AgCl). They are reductively desorbed from the surface at around -1V, leading to research interest in their reductive stability. The goal of my research is to develop reductively stable SAMs on metal surfaces for controlled electrocatalytical analysis. We use hydroquinone attached to SAM as the electroactive redox probe to characterize the desorption process of SAMs on metal surfaces, for the following reasons: 1) there are no other reliable ways to tell the completion of reductive desorption (desorption peak we see on gold cyclic voltammogram is scan rate dependent and can not be seen on other metals like copper due to hydrogen evolution reaction); 2) hydroquinone can be used in basic solution and show redox peaks at more negative potentials, avoid copper oxidation at a more positive potential; 3) hydroquinone is more soluble in aqueous solution than compounds like ferrocene, potentially making the system more dependent on the kinetics of electron transfer. My preliminary data about 11-mercaptoundecyl-hydroquinone SAMs on gold surfaces show that the coverage calculated from hydroquinone oxidation peak decreases as more negative potential is applied and as the applying time increases. With studies on other metal surfaces including silver, copper, we hope to evaluate each kinetic process and relate it to our hypothesis that the extent of filling of the adsorbate antibonding states is the primary predictor for the reductive stability of SAM on different metal surfaces based on d-band model theory.

Characterizing SAM desorption process using Hydroquinone redox probe and Kinetic study on different metal surfaces

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.