Comprehensive study to design advanced metal-carbide@garaphene and metal-carbide@iron oxide nanoparticles with tunable structure by the laser ablation in liquid

Abstract

Core-shell nanoparticles represent a class of materials that exhibit a variety of properties. By rationally tuning the cores and the shells in such nanoparticles (NPs), a range of materials with tailorable properties can be produced which are of interest for a wide variety of applications. Herein, experimental and theoretical approaches have been combined to show the structural transformation of NPs resulting to the formation of either NiFe_xC_y encapsulated in ultra-thin graphene layer (NiFe@UTG) or Ni₃C/Fe_xC_y@FeO_x NPs with the universal one-step pulse laser ablation in liquid (PLAL) method. Analysis suggests that carbon in Ni₃C is the source for the carbon shell formation, whereas the final carbon-shell thickness in the NPs originates from the difference between Ni₃C and Fe_xC_y phases stability at room temperature. The ternary Ni-Fe-C phase diagram calculations reveal the competition between carbon solubility in the studied metals (Ni and Fe) and their tendency toward oxidation as the key properties to produce controlled core-shell NP materials. As an application example, the electrocatalytic hydrogen evolution current on the different NPs is measured. The electrochemical analysis of the NPs reveals that NiFe@UTG has the best performance amongst the NPs in this study in both alkaline and acidic media.

Keywords: Carbon-shell formation; Core-shell nanoparticles; Hydrogen evolution reaction; Metal-carbide; Nickel-iron-carbon ternary phase diagram; Pulse laser ablation in liquid.