Local Structure and Redox Properties of Amorphous CeO2-TiO2 Prepared Using the H2O2-Modified Sol-Gel Method

Abstract

Amorphous CeO2-TiO2 nanoparticles synthesized by the H2O2-modified sol-gel method were investigated in terms of the Ce-O-Ce and Ti-O-Ti linkage, local structure, and redox properties. The decrease in the crystallinity of CeO2-TiO2 by H2O2 addition was confirmed. The metal–oxygen linkage analysis showed the difference in size of the metal–oxygen network between crystalline CeO2-TiO2 and amorphous CeO2-TiO2 due to the O22− formed by H2O2. The local structure of CeO2-TiO2 was analyzed with an extended X-ray absorption fine structure (EXAFS), and the oscillation changes in the k space revealed the disordering of CeO2-TiO2. The decrease in Ce-O bond length and the Ce-O peak broadening was attributed to O22− interfering with the formation of the extended metal–oxygen network. The temperature-programmed reduction of the H2 profile of amorphous CeO2-TiO2 exhibited the disappearance of the bulk oxygen reduction peak and a low-temperature shift of the surface oxygen reduction peak. The H2 consumption increased compared to crystalline CeO2-TiO2, which indicated the improvement of redox properties by amorphization.

Heterogeneous Hollow Multi‐Shelled Structures with Amorphous‐Crystalline Outer‐Shells for Sequential Photoreduction of CO2

“…The high‐resolution TEM image of one subunit on the outer‐shell in Figure 2d indicates two distinct regimes: the crystalized CeO 2 phase and the amorphous TiO 2 phase (Figure S5). Corresponding fast Fourier transformation (FFT) patterns of the two regimes further verify the differences in their crystal lattices, which shows the replacement of the sharp scattering patterns with a blurry halo (insets in Figure 2d) [21] . The variations of the electronic structures in A‐TiO 2 are revealed by electron energy loss spectroscopy (EELS) of Ti L 2,3 ‐edge (Figure 2e and Figure S6, S7).…”

“…Six (3E g +2B 1g +A 1g ) Raman‐active modes of anatase TiO 2 disappeared in the CTHoMSs, leaving only E g peak at around 145 cm −1 and F 2g peak at around 465 cm −1 corresponding to the Ti‐O‐Ti and Ce‐O‐Ce vibrations, respectively [24] . The broader E g peak and negligible F 2g peak shown in the Raman spectrum of A‐TiO 2 HSs further evidence the Ce‐doping behavior in the forming of A‐TiO 2 phase [21] . The changes of electronic structures and coordination environments of Ti and Ce central ions in CTHoMSs are further investigated by X‐ray absorption near edge structure (XANES) spectra.…”

“…Corresponding fast Fourier transformation (FFT) patterns of the two regimes further verify the differences in their crystal lattices, which shows the replacement of the sharp scattering patterns with a blurry halo (insets in Figure 2d). [21] The variations of the electronic structures in A-TiO 2 are revealed by electron energy loss spectroscopy (EELS) of Ti L 2,3 -edge (Figure 2e and Figure S6, S7). The featured t 2g -e g split states of Ti-3d orbital in [TiO 6 ] 8À octahedral unit show obvious change, as the intensities of peaks attribute to the t 2g sub- bands significantly decreased.…”

“…[24] The broader E g peak and negligible F 2g peak shown in the Raman spectrum of A-TiO 2 HSs further evidence the Ce-doping behavior in the forming of A-TiO 2 phase. [21] The changes of electronic structures and coordination environments of Ti and Ce central ions in CTHoMSs are further investigated by X-ray absorption near edge structure (XANES) spectra. As shown in Figure 2g, the negative shifts of Ti K-edge are observed for samples containing A-TiO 2 counterparts, indicating lower Ti-O coordination numbers.…”

CeO2 Nanoparticles Modified on Graphite Sheet Electrodes for Photoelectrochemical Tobacco Wastewater Detection, Degradation, and Toxicity Measurement

“…17 The crystalline nature of the CeO 2 NPs was confirmed by the selected area electron diffraction (SAED) pattern with bright circular spots corresponding to (1 1 1), (2 0 0), (2 2 0), (3 1 1), (2 2 2), (4 0 0), (3 3 1), and (4 2 0) planes (Figure 2b). Due to its crystalline imperfections, 18 there were no additional rings visible in the SAED pattern. The energy-dispersive spectrometry (EDX) pattern (Figure 2c) confirmed the atomic weight percentage of the elements Ce and O present in CeO 2 .…”