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

Abstract

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 °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.