Understanding the Curvature Effect on the Structure and Bonding of MoC_y Nanoparticles on Carbon Supports

High Resolution Image Download MS PowerPoint Slide The interaction between molybdenum carbide (MoC y ) nanoparticles and both flat and curved graphene surfaces, serving as models for carbon nanotubes, was investigated by means of density functional theory. A variety of MoC y nanoparticles with different sizes and stoichiometries have been used to explore different adsorption sites and modes across models with different curvature degrees. On flat graphene, off-stoichiometric MoC y featuring more low-coordinated Mo atoms exhibits stronger interaction and increased electron transfers from the carbide to the carbon substrate. This preferentially occurs through support C and Mo atoms leading to the formation of additional Mo–C bonds. Notably, the MoC y adsorption strength increases on concave surfaces and decreases on convex surfaces, showing a strong linear correlation with the surface curvature. This curvature-dependent behavior alters the charge state of the nanoparticles, making them more/less positively charged in concave/convex regions. The present results demonstrate that the interaction strength can be effectively tuned by manipulating the carbide stoichiometry, the substrate curvature, and the local concave/convex environments, providing valuable guidelines for the rational design of MoC y /C-based catalysts.