Ilya Vinogradov, Suryansh Singh, Hanna Lyle, Michael Paolino, Aritra Mandal*, Jan Rossmeisl, and Tanja Cuk*
Nature Materials, 2022, 21, 88. DOI: 10.1038/s41563-021-01118-9
News Article: https://www.colorado.edu/mse/2021/12/16/cuk-research-group-isolates-reaction-step-describes-energetics-catalysis-materials
Theoretical descriptors differentiate the catalytic activity of materials for the oxygen evolution reaction (OER) by the strength of oxygen binding in the reactive intermediate created upon electron transfer. Recently time-resolved spectroscopy of (photo)-electrochemically driven OER followed the vibrational and optical spectra of this intermediate, denoted M-OH*. However, these inherently kinetic experiments have not been connected to the relevant thermodynamic quantities. Here, we discover that picosecond optical spectra of the Ti-OH* population on lightly doped SrTiO3 are ordered by the surface hydroxylation. A Langmuir isotherm as a function of pH extracts an effective equilibrium constant relatable to the free energy difference of the first OER reaction step. Thus, time-resolved spectroscopy of the catalytic surface reveals both kinetic and energetic information of elementary reaction steps, which provides a critical new connection between theory and experiment by which to tailor the pathway of water oxidation and other surface reactions.