Surface facet dependence of Ru and Ru-based alloy oxidation resistance using ab initio thermodynamics calculation

Recent studies exemplify the high activity of Ru for electrochemical catalytic reactions. However, among these reactions, Ru catalysts are known to easily oxidize with accompanying metal dissolution in the aqueous solution. Therefore, materials design for Ru-based materials should take into consideration its high oxidative property. In this study, we take into consideration the effective facet energy to describe surface energy and evaluate facet dependence of oxidation resistance. The effective facet energy is expressed as an energy correction to the bulk cohesive energy that minimizes layer dependence of surface energy calculation. We used this surface corrected energy to simulate the Pourbaix diagram of the first oxidation of Ru to Ru2O3 as a function of surface facets using Ab Initio thermodynamics calculations. Results show that there is a relatively higher potential for oxidation on the Ru (0001) facet as compared with the Ru (101¯0) facet, predicting that the former facet shows higher oxidation resistance. We further extend our analysis on the oxidation of RuIr alloy and found that the oxidation potential is increased through alloying. Similarly, a relatively higher oxidation resistance on the RuIr (0001) are observed as compared with the RuIr (101¯0). These results are important for materials design that considers control of the surface termination.