Atomic-Scale View on the H2O Formation Reaction from H2 on O-Rich RuO2(110)

Abstract

The H2O formation reaction from H2 on O-rich RuO2(110) was studied by temperature-programmed desorption and reaction (TPD/TPR) and scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations. On the one hand, following H2 adsorption at 270 K, our TPD/TPR measurements reveal that the on-top O species (Oot) enhances the sticking probability of H2, thus facilitating the H2 adsorption and dissociation on O-rich RuO2(110). On the other hand, for low H2 adsorption temperature (170 K), the limited mobility of Had species hinders H2 adsorption at a high coverage of preadsorbed Oot. To better understand the strong influence of the adsorption temperature and the interplay between coadsorbed species, we conducted DFT calculations and high-resolution STM measurements. Two distinct adsorbate configurations, Had–Oot and Oot–Had–Oot, are identified by STM. Mechanisms and molecular models for H2 dissociation and Had diffusion on O-rich RuO2(110) are proposed.