Dissociative adsorption of H2O and CO2 on the clean and O-pre-covered high index Ru surfaces: Corrugated Ru(11−21) and stepped Ru(20−21) surfaces

Abstract

Periodic density functional theory (RPBE) computation has been used to assess dissociative adsorption of H2O and CO2 on the clean and O-pre-covered Ru(11−21) and Ru(20−21) surfaces. It is found that surface H2O prefers desorption on the clean Ru(11−21) and Ru(20−21) surfaces, while dissociative adsorption on O-pre-covered Ru(11−21) and Ru(20−21) surfaces, in contrary to that on O-pre-covered Ru(0001) surface. The H2O dissociation capability on these clean and O pre-covered Ru surfaces follows a sequence of Ru(11−21) > (20−21) > (0001). In addition, CO2 desorption energy is comparable with the barrier of CO2 dissociation on Ru(11−21) and Ru(20−21) (0.81 vs. 0.77 eV, 0.14 vs. 0.20 eV, respectively), indicating that CO2 would not desorb in quantity before it occurs dissociation, which is contrary to the case on Ru(0001) (-0.32 vs. 0.23 eV). For surface O removed via H2O or CO2 formation, H2O formation has lower effective barrier than CO2 formation on these three Ru surfaces, in line with the experiments, and the effective barrier of H2O and CO2 formation follows the increasing order of Ru(11−21) < (20−21) < (0001).