Paper NS-WeM10
In Situ Investigation of Oxidation State and Reactivity of a Cu Model Catalyst by Simultaneous Mass Spectrometry and Indirect Nanoplasmonic Sensing

Wednesday, November 12, 2014, 11:00 am, Room 304

The activity of a catalyst depend on a wide range of factors such as elemental composition, particle dispersion and the oxidation state of the active material. All of these properties can change during operation, reversibly or irreversibly, thereby severely influencing the catalysts performance. It is therefore of great importance to learn how the fundamental properties of a catalyst change during use and to correlate these changes with changes in activity and selectivity. This requires simultaneous, in-situ measurements of both fundamental catalyst properties and activity, a far from trivial task. Here we present a novel quartz-tube micro flow-reactor in which optical spectroscopy and mass spectroscopy can be performed simultaneously. The optical setup is based on indirect nanoplasmonic sensing, which utilizes the localized surface plasmon resonances of Au-discs embedded in Si₃N₄ to detect subtle changes in the oxidation state of a material. We investigate CO-oxidation on a model catalyst consisting of Cu nanoparticles formed by thin film evaporation and subsequent annealing. From these measurements we demonstrate the correlation between oxidation state of the Cu-catalyst and onset temperature for CO₂ formation in gas mixtures with various CO/O₂ ratios. The changes in oxidation state were then confirmed by XPS.