X-ray Absorption and Photoelectron Characterization of Carbon Shell Extracted from Ni@C Nanoparticles

Abstract

Ni@C nanocomposites and the carbon shells extracted by etching Ni@C in nitric acid have been characterized by means of soft X-ray absorption and X-ray photoelectron spectroscopies. It was found on the base of Ni 2p X-ray absorption spectra and atomic multiplet calculations that Ni traces in the carbon-shell sample are in the Ni2+ state formed probably by nickel nitrate hexahydrate, Ni(NO3)(2)6H(2)O. Second derivatives of C 1s of X-ray absorption spectra and C 1s X-ray photoelectron spectra were used for characterization of functional groups linked to carbon shells of nanocomposites. The application of second derivatives of C 1s of X-ray absorption spectra allowed to confirm AA stacking of carbon layers for highly oriented pyrolytic graphite. The low-energy features in C 1s XAS spectra of Ni@C and carbon-shell samples are found to be of a different nature. Most likely, the low-energy C 1s XAS feature of the carbon-shell sample is formed due to hydrogenation of carbon atom.