Computational Design of Spinel Oxides through Coverage-Dependent Screening on the Reaction Phase Diagram

Binary spinel-type metal oxides provide additional opportunities to achieve various catalytic reactions. However, the complexity of the catalytic reaction network, particularly the one containing lattice O involved steps on oxide surfaces, makes it difficult to parse reliable reaction mechanisms. It further challenges the accurate description of catalytic activity in the computational design of catalysts. Therefore, in this work, the rational design of spinel oxides was set out with all elementary steps considered on either perfect or defect sites with also lattice O involved steps. As a result, 2108 possible reaction pathways were enumerated within a complete reaction network for HCl oxidation as a model reaction. The strategy of energy global optimization was performed to obtain favored mechanisms within all possible pathways, building an "energy level" activity trend, namely, the "reaction phase" diagram (RPD). The activity screening for 18 spinel oxides was conducted by descriptors on the RPD. Taking care of the poisoning effect by chloride on the surface, the coverage-dependent screening was performed to search more reliable candidates on the "energy level" trend. Six spinel oxides were finally selected from the coverage-dependent screening on the RPD, where the theoretical activity trend was validated by experiments. At the end, a rigorous rate calculation was performed by the coverage self-consistent microkinetic modeling on the most active surface (CuCo2O4). The reliability of models and approximations used in the scheme of coverage-dependent screening on the RPD, together with the importance of coverage effect, were discussed.