Adsorption of reactants and reaction intermediates on solid catalytic surfaces can lead to significant changes of the surface structure, including, as shown in high-pressure Scanning Tunneling Microscopy (STM) experiments, ejection of metal atoms and formation of metal clusters while the reaction is taking place. Depending on the specific system, these clusters provide new, more favorable reaction paths than the typically considered active sites. In this talk, we will attempt to provide a more realistic picture of the catalyst’s surface and its active sites as a function of reaction conditions and the identity of reactants and that of key intermediates. Surface structure sensitivity, alloying, adsorbate coverage, and nanoparticle size effects will be discussed. These phenomena are directly related to nanoparticle sintering and have important consequences for catalyst stability. Insights derived from our analysis can inform the design of new catalysts with improved activity, selectivity, and stability characteristics.
