Surface structure and stoichiometry of PdZn alloys under realistic (<i>T</i>, <i>p</i>) conditions

PdZn is known to efficiently catalyze CO₂ to methanol. However, the microscopic understanding of the underlying chemical reactions is lacking, e.g., the stoichiometry and structure of the surface under catalytic T, p conditions. The talk will address the first and crucial step for an improved understanding for predicting better catalysts in the family of bi- and tri-metallic materials. Specifically, we will analyze the composition and structure of PdZn(101) in a constrained thermal equilibrium with CO₂ and H₂ gases using ab initio atomistic thermodynamics (aiAT) [1], considering a bulk composition of 1:1. Exposure to H₂ induces a restructuring of the surface and an enhancement of the Pd concentration due to the stronger Pd-H bonds compared to Zn-H. Moreover, the adsorption of CO₂ is stronger in the presence of surface hydrogen. We discuss the restructurings, order/disorder adsorbate phases, and the possibility of the formation of a surface hydride. As anharmonic contributions may play a noticeable role in these systems, we also present benchmark studies using the recent advancement of the classical aiAT approach by our Replica-Exchange Grand-Canonical method [2].


[1] K. Reuter and M. Scheffler, Phys. Rev. B. 65, 035406 (2001).
[2] Y. Zhou, et al., Phys. Rev. B. 100, 174106 (2019).