First Principles study of enhanced stability of Au@Pt nanoparticles on MoS₂ support through alloying kinetics

Two-dimensional MoS₂ supported Pt and Au@Pt nanoparticles (NPs) have received great attention for various catalysis applications. Deep understanding on the NPs migration and coalescence under different service conditions is crucial to enhance their stability. Herein, we employ first-principles density functional theory calculations to study the stabilities and diffusion kinetics of supported Au@Pt NPs at room temperature up to 400 °C in atmospheric hydrogen and vacuum environments. We show that Pt at the bottom layer of the NP interacts strongly with the MoS₂ substrate resulting in a strong adhesion energy. However, the adhesion energy is reduced in hydrogen environment due to strong Pt-H interactions. Further, we show that smaller NPs are more favored in alloy form rather than core/shell due to the facile diffusion kinetics at the edges. Our results are validated using transmission electron microscopy, showing that small size Au@Pt alloy NPs are more stable than the larger ones with the Au core in contact with MoS₂ substrate and Pt shell in contact with hydrogen. The present work gives insights to the degradation mechanisms of the NPs supported on substrates and offers strategies to enhance their stability.