(25g) Rational Design of Bimetallic Catalysts for Total Oxidation Reactions

Bimetallic catalysts possess unique characteristics by improving the catalytic activity synergistically as compared to their single metal counterparts. However, due to complex nature of these systems a huge number of bimetallic structures need to be screened to find good bimetallics. Use of first principle calculations is proving to be extremely useful in design of novel catalysts but for complex reactions, this is a time consuming and cumbersome task. We propose that identification of suitable bimetallics for a particular reaction can be achieved by combining experiments and quantum mechanical calculations. A volcano type relation can be drawn between experimental catalyst activity and binding energy (BE) of atoms that make up a compound. In the case of hydrocarbons, the C BE can be used as a descriptor.

In this study, a framework is introduced that combines synergistically the strengths of high throughput experiments (HTE) and DFT calculations for predicting novel core-shell catalyst structures of bimetallics. In essence, experimental data is injected at the mesoscale of the multiscale ‘ladder’ while leveraging quantum mechanical first principles information. Experimentally estimated reaction rates using the HTE, normalized with the number of active sites measured by chemisorption, are correlated with the atomic binding energies of the heteroatoms to predict optimal properties. Subsequently, informatics tools are employed to match the properties of core-shell structures predicted via DFT with those of the experimentally correlated values. The potential bimetallic structures are tested computationally for their stability using segregation energy calculations under relevant catalyst working conditions. The stable potential candidates are finally synthesized and assessed experimentally. Propane total oxidation is considered as the probe reaction because oxidation is a key in after-treatment catalysis to minimize emissions in transportation and stationary power generation and in energy generation for portable and distributed energy production using microtechnology.

In summary, this study consists of a novel approach that bypasses the creation of complex reaction mechanisms from first principles on one hand and the unguided high throughput experimental search on the other. Utilization of the proposed methodology resulted in a more active and cheaper catalyst than platinum for propane total oxidation.