Title: Dynamic Nanocatalysts: Environmental Effects.
When: Friday, 14th December, 2018, at 12:00.
Place: Sala de Seminarios, Módulo 03, Facultad de Ciencias, Universidad Autónoma de Madrid.
Speaker: Beatriz Roldán Cuenya, Department of Interface Science, Fritz-Haber Institute of the Max Planck Society, 14195 Berlin, Germany.
In order to comprehend the catalytic performance of metal nanostructures, their dynamic nature and response to the environment must be taken into consideration. The working state of a nanocatalyst might not be the state in which the catalyst was prepared, but a structural and/or chemical isomer that adapted to the particular reaction conditions. Furthermore, deactivation phenomena taking place under reaction conditions can only be understood, and ultimately prevented, if sufficient information is available on the catalyst morphology, structure, chemical state, and surface composition while at work.
I will first describe novel approaches for the synthesis of size- and shape-controlled nanoparticles and nanostructured metallic films (e.g. Au, Cu, Ag, Zn, CuZn, CuNi) and their functionalization/activation based on plasma treatments. Subsequently, I will illustrate how to follow the evolution of their morphology and surface composition under different gaseous and liquid chemical environments in the course of a catalytic reaction. This will be implemented using a synergistic combination of in situ and operando microscopy (EC-AFM, STM, TEM) and spectroscopy (XAFS, NAP-XPS) methods. It will be highlighted that for structure-sensitive reactions, catalytic activity, selectivity, and stability can be tuned through controlled synthesis. Examples of catalytic processes which will be discussed include the gas- and liquid-phase oxidation of 2-propanol and the gas-phase thermal hydrogenation and electrochemical reduction of CO2. Emphasis will be given to elucidating the role of the size, shape, composition, chemical state, surface defects and roughness of the catalysts in the activity and selectivity of the former reactions. These results are expected to open up new routes for the reutilization of CO2 through its direct conversion into valuable chemicals and fuels such as methane, ethylene, methanol and ethanol.