Effect of Fe oxidation state (+2 versus +3) in precursor on the structure of Fe oxides/carbonates-based composites examined by XPS, FTIR and EXAFS

Green and Efficient Al-Doped LaFexAl1–xO3 Perovskite Oxide for Enhanced Phosphate Adsorption with Creation of Oxygen Vacancies

“…With the increasing Al-doped content, the electron binding energy of La 3d tends to increase (0.3–0.8 eV), which indicates that when the covalent nature of La–O decreases, lattice oxygen may participate in phosphate adsorption. , With increasing Al-doped content, the electron binding energies of Al 2p (Figure c) and Fe 2p (Figure d) tend to increase and decrease, respectively; Al doping may cause a change in the Fe valence state . The XPS spectra of the Fe 2p region can be fitted into peaks at ∼708.7–710.5 and 723–724 eV belonging to Fe 2+ and at 710.5–712.6 and 724.8–725.9 eV belonging to Fe 3+ (Figure d). ,, After doping with Al, the ratio of Fe 2+ /Fe 3+ tends to increase, indicating that additional Fe 3+ is converted to Fe 2+ (Table S2), which may generate oxygen vacancies and adsorb oxygen on the surface because of charge compensation. The O 1s region of LaFe 1– x Al x O 3 was deconvoluted into two peaks at ∼527–529 and 529.5–531 eV, which belong to lattice oxygen and adsorbed oxygen, respectively. , The lattice oxygen (O lat ) is primarily La–O, Fe–O, and Al–O, and the adsorbed oxygen (O ads ) is primarily the oxygen vacancy formed by physically and chemically adsorbed water, hydroxyl oxygen, O lat point defects, line defects, and surface defects (Figure e). , The ratios of adsorbed oxygen to lattice oxygen of LFO, LFAO-1, LFAO-2, LFAO-3, and LFAO-4 are 0.68, 0.84, 1.16, 1.33, and 1.35, respectively (Table S2).…”

“…40 The XPS spectra of the Fe 2p region can be fitted into peaks at ∼708.7−710.5 and 723−724 eV belonging to Fe 2+ and at 710.5−712.6 and 724.8−725.9 eV belonging to Fe 3+ (Figure 3d). 42,50,51 After doping with Al, the ratio of Fe 2+ /Fe 3+ tends to increase, indicating that additional Fe 3+ is converted to Fe 2+ (Table S2), which may generate oxygen vacancies and adsorb oxygen on the surface because of charge compensation. The O 1s region of LaFe 1−x Al x O 3 was deconvoluted into two peaks at ∼527− 529 and 529.5−531 eV, which belong to lattice oxygen and adsorbed oxygen, respectively.…”

LTA and FAU-X Iron-Enriched Zeolites: Use for Phosphate Removal from Aqueous Medium

“…The existence of Fe oxides in the hydrothermally synthetized zeolites was identified in the FTIR spectrum. There were determined changes in the absorption band at 567 cm −1 which represent the vibrations of Fe–O and Fe–O–Fe bonds [ 30 ]. Additionally, there are some bands between 3400 and 3600 cm −1 and the band at 1640 cm −1 , which are assigned to the OH groups of adsorbed and zeolitic water, respectively.…”

Regulation of bulk reconstruction of FeNiMoO4via NH3 treatment for high performance water oxidation

“…3f) could be further ascribed to two kinds of Fe 3+ species, with peaks at 711.2 eV and 713.8 eV for Fe 3+ (A) and Fe 3+ (B), which might originate from different coordination environments. 27,28 Fe 3+ (B) with a higher BE is suggested to intimately coordinate with Ni via the active bridged O, 29,30 the content of which is over 2 times on FeMoNi–N/NF-2h (68.8%) more than that on FeMoNi–O/NF-2h (33.7%). Combined with the above electron microscopy results, the higher portion of Ni 3+ and Fe 3+ (B) could be ascribed to the prominently evolved γ-Ni(Fe)OOH species on FeMoNi–N-2h.…”