Spectroscopy

Operando Characterization of Electrocatalysts. The dynamic changes in the catalyst structure during reactions create significant difficulties for establishing structure-activity correlations. In my previous research, vibrational spectroscopy was used to characterize the local structure of working catalysts and identify surface reaction species. Using operando Raman spectroscopy, a reversible potential-dependent change in the structure of Ni-modified cobalt (oxy)hydroxides was identified during the oxygen evolution reaction (OER) (Figure 1). Such reversible change was only captured during catalysis and was determined to be essential for the formation of catalytically active structure for OER. In a separate study, operando FTIR was used to examine the chemical change of pyridine—a proposed molecular catalyst in electrochemical CO₂ reduction. My experience in operando spectroscopy will allow me to characterize working catalysts successfully in my future research.

Electrochemical Tip-Enhanced Raman Spectroscopy. I have used tip-enhanced Raman spectroscopy (TERS) to probe the structure of active sites and identify catalyst deactivation mechanisms for the oxygen reduction reaction (ORR). TERS is a technique that combines scanning probe microscopy and Raman spectroscopy to provide correlated chemical and structural information. In my research, I have used TERS techniques based on the atomic force microscopy (AFM-TERS) and scanning tunneling microscopy (STM-TERS) configurations. Using STM-TERS, I have correlated the irreversible degradation of iron phthalocyanine (FePc), a model catalyst for ORR, with the demetallation of this molecule during catalysis (Figure 2, published). This work clarified the catalyst degradation pathway in ORR, a highly-debated topic in the fuel cell community. In a similar study, a partially reduced cobalt phthalocyanine was identified as the dominant species during ORR catalysis using STM-TERS (published). My experience with building and operating STM-TERS and AFM-TERS places me in an excellent position to implement this technique in my proposed research.