Hybrid catalysts composed of molecular catalysts immobilized onto nanocrystals or electrodes offer a promising approach for the rational design of photo-, electro- and photoelectron- catalytic systems. The design and improvement of such hybrid catalysts require the understanding of effect of the electrode and electrode/liquid interface on the structure and dynamics of catalysts. In this presentation, we discuss two unique properties of attached molecular catalysts, induced by the interaction with the nanocrystals and electrodes. In the first topic, we demonstrate Fano Resonance resulted from the interaction of the intraband transition of the photogenerated electrons in quantum confined semiconductor nanocrystals with the vibrational modes of adsorbed molecules. Using transient IR spectroscopy we show that the excitation of CdS or CdSe nanocrystals lead to intense Fano Resonance spectral signatures at the CO stretching vibrational modes of adsorbed molecular catalysts, [Fe2(cbdt)(CO)6] (FeFe; cbdt=1-carboxyl-benzene-2,3-dithiolate), a molecular mimic for the active site of FeFe-hydrogenase. The occurrence of Fano resonances is independent of nanocrystal types (rods vs dots) or charge transfer character between the nanocrystal and FeFe, and is likely a general feature of nanocrystal and molecular catalyst hybrid systems. These results provide new insights into the novel interactions in these hybrid assemblies for artificial photosynthesis In the second topic, we discuss the electrode induction effect of electrode polarization on the charge density on the catalytic metal center. Vibrational sum frequency generation (VSFG) spectroscopy is an in situ interface specific technique capable of probing electrochemical interfacial properties at the molecular level. In this talk, we discuss our recent efforts in developing and applying VSFG for studying the structural and dynamics of a series of rhenium bipyridyl CO2 reduction catalysts on semiconductor and metal electrodes. We have shown that by combining VSFG experiment with ab initio computational studies, catalyst adsorption geometry can be determined. Through electrochemical Stark effect of the CO stretching model, local electric field at the electrode-solution interface can be directly measured and its effect on the charge density of metal center can be quantified.

Fano resonance and electrode induction effect of molecular catalysts on electrode surfaces

ACS Spring 2022

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