ATOMIC DISPERSED PT AND AU ATOMS ON ZNO SURFACE FOR METHANOL STEAM REFORMING

摘要

In heterogeneous catalysis, metal particles are used to catalyze various industrially important chemical processes. To effectively utilize the desired, often expensive, precious metal, one usually disperses them onto high-surface-area supports with sizes ranging from a few nanometers down to subnanometers. The presence of a large number of low-coordination sites on small particles is thought to be responsible for the enhanced catalytic activity. To fully understand the structure-reactivity relationship of small particles or clusters, however, requires detailed knowledge of the active sites at the atomic level, which are often not available. Alternatively, metal species atomically dispersed onto oxide supports provide a well-defined system and have demonstrated excellent catalytic performance. Moreover, such systems can provide a new platform to mimic homogeneous catalysis under heterogeneous environment. Due to the recent advances of atomic resolution and in-situ characterization techniques, there are increasing interests on studying atomically dispersed catalysts. Furthermore, it is found that the active centers, responsible for the low temperature activity of water-gas-shift reaction and CO oxidation, can be attributed to the function of individual precious atoms strongly anchored onto the surfaces of oxide supports. Although the atomically dispersed catalysts may open a new and probably an efficient way to design novel classes of heterogeneous catalysts, it remains a challenge to fully uncover the nature of the active sites, to significantly improve their performance, and to develop strategies to prolong the stability of single-atom catalysts.