Active Site Engineering via Optimizing Heterogeneous Support Structure for Single Atom Catalysis

Abstract

Supported single-atom catalysts (SAC) show a large range of activity and selectivity that depend on the local environment of the catalytic sites. A theory-based optimization strategy is presented based on a density functional theory (DFT) determination of the transition states and intermediates for a low-dimensional coordinate representation of the heterogeneity of the active sites. The approach is applied to a vanadium catalyst on an amorphous SiO2 support that involves a large kinetic network described using a full-chemistry model. Without assuming a priori scaling relations or mechanism reduction, the optimal state of heterogeneity is found to lie at atomic configurations where the activation energies for two distinct key chemical processes are equal. It is found a posteriori that the behavior of the system is consistent with linear free energy scaling relations in the randomness parameters. The energetic span theory proves quite useful in reducing the full chemistry model to a small number of key reactions. The use of a nonlinear optimization algorithm in combination with energetic span theory provides significant simplification in treating disordered systems.