In situ genesis of selective adsorption sites by complex catalytic redox dynamics

Abstract Several in situ studies have revealed spatiotemporal dynamics on heterogeneous catalysts surfaces under chemical stimuli1-4, which presumably control the activity, selectivity, and productivity5-11. However, operando validations of sufficient spacetime resolution12 are often missing, and hence, the effect of these dynamics on catalytic performance may not be entirely clear. Here, using dry reforming of methane over Ni as an example, we demonstrate the relevance of catalytic redox dynamics for reaction performance and determine their genesis from adaptive chemistry and continual catalytic cycling. By combining operando scanning electron microscopy and near-ambient-pressure X-ray photoelectron spectroscopy, we found that activation sites for methane and carbon dioxide differed but continually transformed into each other during the reaction. This behavior enabled a self-sustained oscillating regime evincing the sequential formation of active sites. We also found that not all spatiotemporal dynamics accounted for the catalytic function. We highlight the importance of oscillating reactions for mechanistic studies and propose that the generation of mechanical strain at the catalyst during redox cycling acted as a feedback element for the oscillations. These observations lead to deeper understanding of fundamental catalysis and open new opportunities for tuning catalytic performances.