Correlative in situ microscopy of hydrogen oxidation on rhodium: from the meso- to the nanoscale

Abstract

Catalytic surface reactions, such as CO oxidation, may produce a variety of spatio-temporal effects on the catalyst surface. To reveal the mechanisms behind such spatio-temporal effects, it is advantageous to apply multiple techniques to the same samples, particularly at different length scales. In other research areas than catalysis this idea has led to the correlative microscopy approach. In catalysis, this approach is, if at all, used for sample characterization, often in two separate setups. In the present contribution, the correlative microscopy approach has been applied in situ to the catalytic hydrogen oxidation on rhodium to reveal the mechanism of multifrequential kinetic oscillations, a novel effect recently detected in this reaction. Such oscillations were first observed on a polycrystalline Rh foil, where the reaction oscillated in a self-sustained way between the states of high and low activity (a known behavior), but with different frequencies on adjacent domains (a new and unexpected behavior). Later on, such an effect was also observed on the nanofacets of a Rh tip modeling a single catalytic particle. Such behavior contradicts previous observations and expectations based on the known spatial coupling mechanisms and was never observed before, for any surface reaction.