The reactor-STM:A real-space probe for operando nanocatalysis

"Looking" on the other side of the pressure gap in heterogeneous catalysis is an essential step in identifying and understanding differences and similarities between the behavior of catalysts under actual operation conditions (operando) and under the near-vacuum conditions of traditional laboratory experiments. In this article, we demonstrate that real-space, atomic-scale imaging of active catalyst surfaces is possible under realistic or semirealistic reaction conditions with the reactor-STM, a scanning tunneling microscope that is fully integrated with a miniature flow reactor and housed inside an ultrahigh-vacuum system. This special-purpose instrument combines the merits of standard surface-science methods with operando STM observations of model catalysts in action. We illustrate the strength of this microscope with examples of CO oxidation on platinum surfaces.