A Water-Promoted Mars−van Krevelen Reaction Dominates Low-Temperature CO Oxidation over Au-Fe <sub>2</sub> O <sub>3</sub> but Not over Au-TiO <sub>2</sub>
Alexander Holm, Bernadette Davies, Sara Boscolo Bibi, Félix Moncada, Joakim Halldin-Stenlid, Laurynas Paškevičius, Vincent Claman, Adam Slabon, Cheuk‐Wai Tai, Egon Campos dos Santos, Sergey Koroidov
Abstract
High Resolution Image Download MS PowerPoint Slide We provide experimental evidence that is inconsistent with often proposed Langmuir−Hinshelwood (LH) mechanistic hypotheses for water-promoted CO oxidation over Au–Fe 2 O 3 . Passing CO and H 2 O, but no O 2, over Au-γ-Fe 2 O 3 at 25 °C, we observe significant CO 2 production, inconsistent with LH mechanistic hypotheses. Experiments with H 2 18 O further show that previous LH mechanistic proposals cannot account for water-promoted CO oxidation over Au-γ-Fe 2 O 3 . Guided by density functional theory, we instead postulate a water-promoted Mars–van Krevelen (w-MvK) reaction. Our proposed w-MvK mechanism is consistent both with observed CO 2 production in the absence of O 2 and with CO oxidation in the presence of H 2 18 O and 16 O 2 . In contrast, for Au-TiO 2, our data is consistent with previous LH mechanistic hypotheses.