Ultraviolet photoelectron spectra (UPS) of lithium nickel oxide (LixNi2−xO2, 0 < x ≤ 1.0) solid solution were measured using a synchrotron radiation light source. The upper valence UPS are confirmed to consist of five structures for Eb < 15 eV. The electronic density of two O2p states changed as the compositional ratio of Li and Ni. After a contact reaction of LiNiO2 and methane gas, the peak intensity of one of two O2p states decreased remarkably. It was found that the surface oxygen at the lower binding energy was selectively contributed to dissociate σ-bond between carbon and hydrogen of methane.
Lithium nickel oxides Ultraviolet photoemission spectroscopy Valence band structure Oxidative coupling of methane Selective oxidation
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The authors acknowledge the staff of the UVSOR Facility of the Institute for Molecular Science and the Photon Factory for their helpful advice and technical support. The present study has been performed under the approval of the Photon Factory Advisory Committee (PF PAC No. 2009G615).