In situ observation of oscillatory redox dynamics of copper
Jing Cao, Ali Rinaldi, Milivoj Plodinec, Xing Huang, Elena Willinger, Adnan Hammud, Stefan Werner Hieke, Sebastian Beeg, Luca Gregoratti, Claudiu Colbea, Robert Schlögl, Markus Antonietti, Mark Greiner, Marc‐Georg Willinger
Abstract
How a catalyst behaves microscopically under reaction conditions, and what kinds of active sites transiently exist on its surface, is still very much a mystery to the scientific community. Here we present an in situ study on the red-ox behaviour of copper in the model reaction of hydrogen oxidation. Direct imaging combined with on-line mass spectroscopy shows that activity emerges near a phase boundary, where complex spatio-temporal dynamics are induced by the competing action of simultaneously present oxidizing and reducing agents. Using a combination of in situ imaging with in situ X-ray absorption spectroscopy and scanning photoemission microscopy, we reveal the relation between chemical and morphological dynamics and demonstrate that a static picture of active sites is insufficient to describe catalytic function of redox-active metal catalysts. The observed oscillatory redox dynamics provide a unique insight on phase-cooperation and a convenient and general mechanism for constant re-generation of transient active sites.