(6h) Elucidating the Influence of Electric Fields on Fe Oxidation Via Multiscale Models and Atom Probe Tomography

One aspect crucial to the design of effective catalysts is knowledge of the elementary reaction mechanism, which is difficult to divine from experiment alone. However, first principle modeling techniques can be used to address this knowledge gap. Earth-abundant, catalytic Fe has been found to be highly selective for hydrodeoxygenation (HDO) reactions but is prone to oxidative deactivation. However, applying a positive external electric field to alter the polarity of the catalytic system can reduce surface oxidation by decreasing the adsorption capabilities of atomic oxygen, thus reducing oxidative deactivation. In this work, we determine the equilibrium oxygen distribution over a single catalytic grain of Fe as the electric field, temperature, and oxygen pressure vary. These models elucidate how oxidation changes with increased electric field strength and experimental conditions. When comparing these models to that of experimental results, we can determine how the formation of Fe oxides depends on the exposed surface facet of a single nanoparticle. We find that our theoretical work agrees with the experimental work: Fe oxidation occurs more rapidly on ‘rough’ surfaces, such as Fe(222) and Fe(002), whereas Fe oxides take longer to form on ‘flatter’ surfaces, such as Fe(110) and Fe(024). The combination of Operando Atom Probe and our computationally derived model opens the perspective for better comprehension of high-field electrochemistry. Reducing oxidative deactivation through application of external electric fields is one way in which we can improve catalyst conditions for successful HDO.