XAFS and XPS studies on the enhancement of methane adsorption by NiO dispersed ACF with the relevance to structural change of NiO

A remarkable enhancement of methane adsorptivity of activated carbon fiber (ACF) with dispersion of ultra fine NiO particles was observed. The Ni K-edge X-ray adsorption near-edge structures (XANES) and extended X-ray adsorption fine structures (EXAFS) spectra of dispersed NiO on ACF elucidated that the dispersed NiO showing the most remarkable enhancement effect has a specific structure whose nearest-neighbor atomic distance of NiO is larger than that of powdered NiO. The X-ray photoelectron spectroscopy (XPS) spectra suggested that the electrons of the ligand valence band in the dispersed NiO are tightly bound than those of the powdered NiO.