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. The advantages of using SAMs to tether catalysts include: 1) facilitating the quantification of tethered catalysts; 2) enabling IR spectroscopy to observe intermediates; 3) making it easy to control surface coverage; 4) modulating electron transfer rates by changing tether length. 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, making it difficult to continue the study. The goal of my research is to develop reductively stable SAMs on metal surfaces for controlled electrocatalytical analysis. We begin with understanding the mechanism and the nature of the bond between sulfur from SAM head group and evaporated gold on silica wafer. We use a combination of in situ X-ray absorption spectroscopy (XAS) and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) to probe the electronic and physical structure of the self-assembled monolayers on metal surfaces during the electrochemical reductive desorption process. By examining the electronic structure and coordination environment of SAM head group and metal surface atoms via XAS, we hope to test 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.

In-Operando X-ray absorption spectroscopic measurements of the reductive desorption of alkanethiol self-assembled monolayers on Au surface

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.