Unveiling the nucleation and evolution of twinned intermetallic nanocrystals for CO-tolerant selective hydrogenation

Revealing the nucleation and dynamic evolution of nanocrystals is of great importance for their application as catalytic materials. For intermetallic nanocrystals, the catalytic performance is closely related to the unique geometrical and electronic structures with ordered atomic arrangements. However, there is a lack of atomic-level understanding of how intermetallic nanocrystals nucleate and the interface structure dynamically evolved under harsh synthesis conditions. Here, we developed a strategy to prepare twinned Pt2Mo intermetallic nanocrystals via regulating the nucleation and growth processes, in which the heating rate and annealing time play principal roles in forming a twinned interface. The results demonstrated that rapid heating rates at the nucleation stage and the short annealing time at 1000 degrees C were favorable for the formation of a twin boundary in Pt2Mo nanocrystals. In situ aberration-corrected scanning transmission electron microscopy unveiled that long-term annealing is unfavorable for twinned nanoparticles due to the melting-assisted transformation of twinned nanoparticles into untwinned Pt2Mo nanoparticles. The twinned Pt2Mo/C constitutes a promising CO tolerant catalyst for the highly selective hydrogenation of nitroarenes. The electron transfer from Mo to Pt increases upon increasing the content of twinned Pt2Mo nanocrystals, thus favoring resistance to a higher concentration of CO. A deep understanding of the dynamic evolution of nanocrystals will help to precisely design the catalyst interface structure down to the atomic level.

Automated summary

Studying the nucleation and dynamic evolution of nanocrystals is crucial for their use as catalytic materials. For intermetallic nanocrystals, their catalytic performance is closely related to their unique geometrical and electronic structures. However, there is currently a lack of understanding about how intermetallic nanocrystals nucleate and evolve under harsh synthesis conditions. In this study, by regulating the nucleation and growth processes, twinned Pt2Mo intermetallic nanocrystals were successfully prepared. The results showed that the heating rate and annealing time played key roles in the formation of twinned interfaces. Furthermore, the study also revealed the unfavorable effect of long-term annealing on twinned nanoparticles, as they transformed into untwinned Pt2Mo nanoparticles. These findings are important for designing catalyst interface structures at the atomic level.