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Abstract

Ultra-fine oxygen-deficient ferrites can decompose CO 2 gas, which causes the greenhouse effect, into C and O 2 at a low temperature of about 300 uC. In the present study, two ultra-fine powders of ternary ferrites of composition (Ni,Zn)Fe 2 O 4 , as potential catalysts for CO 2 decomposition, were prepared by hydrothermal synthesis or a coprecipitation method, and their abilities to decompose CO 2 investigated. X-Ray diffraction measurements identified the crystal structure of the ferrites as spinel-type. The Brunauer-Emmett-Teller (BET) surface area of the ferrite prepared by hydrothermal synthesis was above 110 m 2 g 21 and larger than for the sample obtained by the coprecipitation method. Particle sizes were very small, about 5-10 nm, in the both specimens. The CO 2 decomposition efficiency of the reduced oxygen-deficient ternary ferrite prepared by hydrothermal synthesis was better than that of the coprecipitation sample. The difference of the CO 2 decomposition efficiency is discussed in terms of the morphology and crystallinity based on TEM observations.

Characteristics of Nanosize Spinel Ni_xFe_3-xO₄ Prepared by Sol-Gel Method Using Egg White as Emulsifying Agent

“…By comparing the intensities of the absorption bands associated with Lewis and Brønsted-Lowry acid sites, it can be concluded that the acid characteristic of the samples is dominated by Lewis acid, and there is tendency that the Lewis acid strength increases with increased Ni content in the samples. In the fingerprint region of the spectra, the absorption band representing stretching vibration of Fe-O and bending vibration of Ni-O was detected at 617.22 cm -1 [33][34], suggesting the existence of Fe-O-Ni bond which confirms the formation of Ni x Fe 3-x O 4 structure as expected.…”

“…The acid sites identification is of particular importance since the acidity is acknowledged as a very important characteristic which determines the performance of a material as catalyst [32][33]. The FTIR spectra of four samples investigated are shown in Fig.…”

“…4, the spectra are practically similar in terms of the absorption bands, with only some minor differences in relative intensities and positions of some bands, depending on the Ni/Fe ratio. In general, the peaks appeared at the wavelength range of 3500-3000 cm -1 are assigned to O-H stretching vibration, and the absorption bands located at 630-580 cm -1 and at 480-420 cm -1 are assigned to strong and weak stretching vibrations of M-O modes, respectively [33][34][35]. The presence of M-O modes is supported by the vibration band located at the wavelength of 570-560 cm -1 .…”

Catalytic Conversion of CO2/H2 into Alcohol Using Modified Lampung–Zeolite as Catalyst

“…In In the Fe 2 O 3 doped zeolites samples investigated, as can be seen in Fig. 6, the spectra are pratically similar in terms of the absorption bands for acid sites characteristics, with only some minor differences in intensities and wave numbers, 22,23 .…”

CO2 decomposition over freshly reduced nano-crystallite Cu0.5Zn0.5Fe2O4 at 400–600°C

“…Kim et al [8,9] reported that Ni x Zn 1Àx Fe 2 O 4Àd showed a higher CO 2 decomposition efficiency than NiFe 2 O 4Àd . The decomposition of CO 2 on nano-sized Mn-Zn ferrites and MnNi ferrites was investigated [10].…”