Epitaxial Core‐Shell Oxide Nanoparticles: First‐Principles Evidence for Increased Activity and Stability of Rutile Catalysts for Acidic Oxygen Evolution

Due to their high activity and favorable stability in acidic electrolytes, Ir and Ru oxides are primary catalysts for the oxygen evolution reaction (OER) in proton‐exchange membrane (PEM) electrolyzers. For a future large‐scale application, core‐shell nanoparticles are an appealing route to minimize the demand for these precious oxides. Here, we employ first‐principles density‐functional theory (DFT) and ab initio thermodynamics to assess the feasibility of encapsulating a cheap rutile‐structured TiO(2) core with coherent, monolayer‐thin IrO(2) or RuO(2) films. Resulting from a strong directional dependence of adhesion and strain, a wetting tendency is only obtained for some low‐index facets under typical gas‐phase synthesis conditions. Thermodynamic stability in particular of lattice‐matched RuO(2) films is instead indicated for more oxidizing conditions. Intriguingly, the calculations also predict an enhanced activity and stability of such epitaxial RuO(2)/TiO(2) core‐shell particles under OER operation.