Combining First Principles Theory and Experimental Characterization to Investigate Model Catalyst Surfaces*

The electrochemical interface is relevant in applications such as water purification, corrosion, catalysis, and energy storage. The exact structure and composition of the solid surface crucially impacts ion adsorption, dissolution and intercalation and electron energy alignment between surface and reacting molecules. However, the structure of these surfaces under operating conditions is challenging to probe experimentally and the relevant chemical reaction mechanisms are often unknown. We will review the latest developments and ongoing challenges in building first-principles models for solid-liquid interfaces under electrochemical potential control. Such theoretical models of interfacial structure still rely upon approximations which can be inaccurate for surfaces in complex environments and with defects, highlighting the importance of combining them with experimental characterization methods such as X-ray reflectivity (XRR) and temperature programmed desorption (TPD).  

XRR determines the electron density of an interface with high resolution but typically relies on model-dependent fitting to invert the data and obtain the corresponding atomic structure. We integrate first principles theory with XRR measurements to gain insights into bonding and structure at the Al₂O₃(001)/water interface. TPD determines reactant desorption energy by increasing the temperature of the substrate in a high vacuum environment, but identification of the active sites contributing to peaks in the spectra remains a challenge. We use a combination of TPD and density-functional theory (DFT) to investigate the atomic-scale origin of increased reactivity of small alcohols at under-coordinated sites on Ag(111) and TiO₂/Au(111) model catalysts.