Ni 2p X-ray photoelectron spectroscopy study of nanostructured nickel oxide

Herein the detailed analysis of the Ni 2p X-ray photoelectron spectra of nanostructured nickel oxide samples with three different average crystallite sizes is reported. The observed main line broadening and the increase in the relative intensity of the ∼1.5 eV satellite structure are discussed taking into account the large surface to volume ratio, high concentration of Ni2+ vacancies and enhancement in the Ni 3d–O 2p hybridization. The influence of these factors on the possible local and non-local screening mechanisms accompanying the photoemission of Ni 2p core level electron is analyzed on the basis of the Ni7O36 cluster calculations.