The reduction mechanism of the RuO2(110) surface by molecular hydrogen exposure is unraveled to an unprecedented level by a combination of temperature programmed reaction, scanning tunneling microscopy, high-resolution core level shift spectroscopy, and density functional theory calculations. We demonstrate that even at room temperature hydrogen exposure to the RuO2(110) surface leads to the formation of water. In a two-step process, hydrogen saturates first the bridging oxygen atoms to form (Obr-H) species and subsequently part of these Obr-H groups move to the undercoordinated Ru atoms where they form adsorbed water. This latter process is driven by thermodynamics, leaving vacancies in the bridging O rows.
Corresponding author: H. Over. Reprints also available from M. Schmid (schmid).
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