X-ray Diffraction and X-ray Spectroscopy Studies of Cobalt-Doped Anatase TiO₂:Co Nanopowders

Abstract

Co-doped TiO2 is one of the most extensively studied oxides for applying as dilute magnetic semiconductors due to its room temperature magnetism. Here we present results of the studies of Ti0.97Co0.03O2 nanopowders synthesized by microwave-assisted hydrothermal method by means of X-ray diffraction, soft X-ray absorption spectroscopy (Ti L2,3 and Co L2,3 spectra), hard X-ray absorption spectroscopy (Co K spectra), and 1s3p resonant inelastic X-ray scattering at the Co K edge. According to X-ray diffraction data and Ti L2,3 X-ray absorption spectra, all the samples before the thermal treatment exhibit anatase structure with substantial amount of amorphous phase. After annealing the Ti0.97Co0.03O2 samples in vacuum or hydrogen at 700 °C, the anatase structure persists while amorphous phase contribution is eliminated. Surface-sensitive soft X-ray absorption Co L2,3 spectroscopy revealed only Co2+ ions tetrahedrally coordinated by oxygen ions and no sign of metallic Co. Co2+ tetrahedral sites (instead of typical octahedral ones) are an additional evidence for Co2+ localization at the distorted TiO2 particle surface. Bulk-sensitive X-ray diffraction, Co K X-ray absorption spectroscopy, and 1s3p resonant inelastic X-ray scattering at the Co K edge revealed clustering of metallic cobalt inside of the large agglomerates formed by TiO2 nanoparticles in annealed TiO2:Co nanopowders.

UV/Vis Light Induced Degradation of Oxytetracycline Hydrochloride Mediated by Co-TiO2 Nanoparticles

“…Among various transition metals (i.e., Pt, Ag, Au, Ru, and Pd) [28][29][30][31] and transition metal oxides (i.e., Cu 2 O, α-Fe 2 O 3 ) [32][33][34], cobalt [35,36] and cobalt oxides [37][38][39][40] as an interesting low-cost and earth-abundant mineral have attracted tremendous attention for the development of visible light active TiO 2 materials. Cobalt-doped TiO 2 photocatalysts have been synthesized by various methods, such as the sol/gel technique [36,[41][42][43][44][45][46][47][48][49][50], hydrothermal treatment [51][52][53][54], impregnation method [55,56], precipitation process [57] for the photocatalytic degradation of methylene blue [57,58], rhodamine B [58], methylene orange [57], phenol [41], 2-chlorophenol [41], and so on.…”

Direct observation of the evolving metal–support interaction of individual cobalt nanoparticles at the titania and silica interface

“…2a-d) and are assigned to L I 3 -L III 3 which can be used to distinguish between the oxidation and local coordination state of Co-containing compounds. [43][44][45][46] Notably, the presence of two prominent features (L I 3 and L III 3 ) in both samples indicates that Co is present primarily as high spin Co 2+ species with octahedral (O h ) coordination (i.e. CoO).…”

Magnetic Properties, Electron Paramagnetic Resonance, and Photoelectron Spectroscopy Studies of Nanocrystalline TiO2 Co‐Doped with Al and Fe

“…Agglomeration of :Co nanoparticles after hydrogen or vacuum annealing was discussed in ref. [17].…”