This talk will present periodic density functional theory-based models of proton-coupled electron transfer (PCET) involving well-defined surface sites and defects on solid surfaces. PCET is ubiquitous in electrocatalysis, as many of the elementary steps in electrocatalytic transformations can be classified as PCET processes. Therefore, understanding the atomic-scale factors that govern the thermodynamics and intrinsic kinetics of PCET can inform strategies to tailor reactivity of different catalytic materials. We first describe the impact of the local electrostatic environment and continuous conjugation on the heterogeneous electrochemical PCET reactivity of molecularly defined moieties on carbon surfaces. The PCET thermochemistry of these systems is accurately modeled using both constant-charge and constant-potential DFT methods. Next, we show that the bond dissociation free energies of O–H bonds on anatase TiO<sub>2</sub> surfaces vary widely depending on whether charge-compensating electronic defects are valence p-band holes or conduction d-band electrons. The rate constants of analogous reactions between TiO<sub>2</sub> and a nitroxyl radical PCET oxidant are calculated using vibronically nonadiabtic PCET theory, where the transferring electron and proton are both treated quantum mechanically. Rate constant input parameters such as reorganization energies and the proton vibrational wavefunctions and energy levels are computed using hybrid DFT calculations. These studies describe the impact of the local chemical environment on PCET reactivity, which has implications for catalytic reactions on metal and semiconductor surfaces.

Theoretical models of proton-coupled electron transfer reactions at solid surfaces

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