Dynamics of palladium single-atoms on graphitic carbon nitride during ethylene hydrogenation

Single-atoms on carbon-nitrogen supports are considered catalysts for a multitude of reactions. However, doubts remain whether really these species or subnanometer clusters formed under reaction conditions are the active species. In this work, we investigate the dynamics of palladium single-atoms on graphitic carbon nitride during ethylene hydrogenation and H2-D2 exchange. By employing aberration-corrected scanning transmission electron microscopy, x-ray photoelectron spectroscopy and x-ray absorption spectroscopy, we will show that palladium, originally present as single-atoms, agglom-erates to clusters at 100 degrees C in a gas atmosphere that contains both ethylene and hydrogen. This agglom-eration goes in hand with the emergence of catalytic activity in both ethylene hydrogenation and H2-D2 exchange, suggesting that clusters, rather than single-atoms, are the active species. The results presented herein highlight the potential of analytics over the course of reaction to identify the active species and provide new insights into the influence of gas atmosphere on metal speciation.(c) 2023 Elsevier Inc. All rights reserved.

Automated summary

Single-atoms on carbon-nitrogen supports are considered catalysts for various reactions, but it's uncertain if these species or subnanometer clusters formed during reactions are the active species. This study investigates the behavior of palladium single-atoms on graphitic carbon nitride during ethylene hydrogenation and H2-D2 exchange. The results suggest that palladium aggregates to clusters at 100 degrees C in the presence of ethylene and hydrogen, and these clusters are the active species in catalytic reactions. This research highlights the importance of analyzing the dynamics of catalysts during reactions to identify the active species and understand the influence of gas atmosphere on metal speciation.