(Invited) In Situ Time-Resolved Vibrational Spectroscopic Probe of Catalyst Structures, Dynamics and Reaction Mechanisms on Semiconductor Photoelectrodes

Abstract

Attachment of molecular catalysts onto semiconductor or metal electrodes is a promising approach for rational design of efficient photoelectrochemical cells for solar water splitting and CO2 reduction. The understanding and improvement of such devices requires fundamental understanding of the structure and dynamics of catalysts as well as the interfacial electrolyte environment at electrode-liquid interfaces. Vibrational sum frequency generation (VSFG) spectroscopy is an in situ interface specific technique for probing interfacial properties at the semiconductor electrode/electrolyte interface at the molecular level. In this talk, we discuss our recent efforts in developing and applying in situ time-resolved VSFG for studying structural and dynamics of rhenium bipyridyl and other molecular CO2 reduction catalysts on semiconductor and metal electrodes. We have shown that by combining VSFG experiment with advanced computational modeling, catalyst adsorption geometry can be determined; through electrochemical Stark effect, local electric field and the potential profile in the electric double layer under light and dark conditions can be directly measured; using VSFG as a time-dependent probe, the interfacial charge transfer dynamics can be directly measured and key reactive intermediates can be identified.