Effects of Ni vacancies and crystallite size on the O 1s and Ni 2p x-ray absorption spectra of nanocrystalline NiO

Abstract

We have studied the electronic structure of nanocrystalline NiO thin films, grown by radio-frequency magnetron sputtering under different experimental conditions, using x-ray absorption spectroscopy. The O 1s and Ni 2p spectra showed distinct changes as a function of O2 content in the plasma, which were reproduced with cluster model calculations. These changes are attributed to the incrementing of the surface contribution due to a decrease of the crystallite size as the O2 content in the plasma increases, and to the presence of induced nickel vacancies. Thus, the changes in the electronic structure can be related to the modification of structural and transport properties of these nanocrystalline films.

Degradation of High‐Nickel‐Layered Oxide Cathodes from Surface to Bulk: A Comprehensive Structural, Chemical, and Electrical Analysis

“…In addition, the first peak (a‐peak) of the O K‐edge has a higher intensity for LiNiO 2 than for NiO due to the difference in Ni 3d corresponding to the contribution of the O 2p orbital. [ 54,55 ] Thus, as shown in Figure 6m,n, which depicts the intensity ratio maps of the a‐ and d‐peaks at the O K‐edge, we can obtain results similar to those of the ELNES Ni L 2,3 analysis shown in Figure 6i,j. This finding demonstrates that our analyses of the electronic structures of the Ni L 2,3 ‐edge and O K‐edge in NiO and LiNiO 2 are consistent because the NiO and LiNiO 2 phases show similar distributions in the pristine case and after 500 cycles.…”

Interfacial spin glass mediated spontaneous exchange bias effect in self-assembled La0.7Sr0.3MnO3:NiO nanocomposite thin films

“…9(b), we observe a clear splitting in Ni L2-edge, revealing the Ni 2+ valance state of Ni ion, as expected for NiO, under the octahedral environment. 55 To further substantiate the 2+ state of Ni, we simulated the L2-edge spectra for Ni 3+ and Ni 2+ states using CTM4XAS code 56 and compare them with the experimental data as shown in the inset of Fig. 9(b).…”

Operando observation of nickel/ceria electrode surfaces during intermediate temperature steam electrolysis

“…However, close inspection of the NEXAFS spectra and in particular of the L2-edge (see inset of figure S2), reveals a marginal increase of the peak feature around 872 eV in case of Ni/GDC. In previous works [45], [46] the increase of the peak at 872 eV was attributed to the appearance of Ni 3+ species.…”