Operando Nanocatalysis: Size, Shape, Composition and Chemical State Effects

In order to comprehend the properties affecting the catalytic performance of metal nanoparticles (NPs), their dynamic nature and response to the environment must be taken into consideration. The working state of a NP catalyst 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.
This talk provides examples of recent advances in the preparation, functionalization and characterization of NP catalysts with well-defined sizes and shapes. It discusses how to resolve the shape of nm-sized metal catalysts via a combination of in situ and operando microscopy (AFM, STM, TEM) and spectroscopy (XAFS) methods, and how to follow its evolution under different gaseous or liquid chemical environments in the course of a catalytic reaction. It will be highlighted that for structure-sensitive reactions, catalytic activity, selectivity and stability against sintering 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 reduction of CO₂ in the gas-phase at high pressure as well as electrochemically. Emphasis will be given to elucidating the role of the NP size, shape, composition and chemical state of the catalysts in the activity and selectivity of the former reactions.