In‐situ isothermal micro‐Raman spectroscopy reveals the activation energy of dehydration in α‐FeOOH

Abstract

A real‐time, isothermal micro‐Raman spectroscopy was developed as a single technique for monitoring the solid state kinetics of dehydration and measuring its activation energy. The technique comprises of acquisition and numerical analysis of a set of isothermal time‐dependent Raman spectra. α‐FeOOH transformation to Fe2O3 in N2 atmosphere was continuously monitored for up to 16 h at three temperatures. Dehydration activation energy of 1.4(1) eV was estimated. The Raman band evolution of two modes with different symmetries (B1g ~ 240 cm−1 and Ag ~ 400 cm−1) and the intensity decay of B1g mode at ~540 cm−1 are analyzed independently utilizing kinetic model‐free approach. The study opens new possibilities for developing versatile solid state chemical and bio‐chemical Raman sensors and advances the field of analytical micro‐Raman spectroscopy. Copyright © 2017 John Wiley & Sons, Ltd.

Microstructural Assessment of Magnetite Nanoparticles (Fe3O4) Obtained by Chemical Precipitation Under Different Synthesis Conditions

“…Analyzing the characteristic peaks of each phase, it can be concluded that magnetite phase occurs in the samples Mag-01 to Mag-04 (Figure 3a) and magnetite and maghemite phases occur in the samples Mag-05 and Mag-06 (Figure 3b). There is good agreement in the reported spectra of goethite [17][18][19] with bands at 92, 164, 203, 243, 297, 384, 478, 546 and 663 cm -1 found in some regions of sample Mag-01 (Figure 3c). Table 2 shows the evaluated synthesis parameters and the obtained crystallite size and crystallinity values for all samples, estimated by Scherrer equation.…”

Unraveling the Evolution of Dynamic Active Sites of LaNixFe1–xO3 Catalysts During OER

“…This indicates the formation of α-FeOOH. 52,53 Unlike LaNi 0.5 Fe 0.5 O 3, the modes corresponding to La are not clearly distinguishable.…”

“…Along with this, very broad and less intense bands appear between 200 and 500 cm –1 . This indicates the formation of α-FeOOH. , Unlike LaNi 0.5 Fe 0.5 O 3, the modes corresponding to La are not clearly distinguishable.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XII

“…Sendova, Hosterman, and Grebe used in‐situ isothermal micro‐Raman spectroscopy to reveal the activation energy of dehydration in α‐FeOOH. Their study opens new possibilities for developing versatile, solid state chemical and bio‐chemical Raman sensors and advances the field of analytical micro‐Raman spectroscopy . Sun et al reported pressure‐induced Fermi resonance between the fundamental modes in 7,7,8,8‐tetracyanoquinodimethane.…”

“…Their study opens new possibilities for developing versatile, solid state chemical and bio-chemical Raman sensors and advances the field of analytical micro-Raman spectroscopy. [214] Sun et al reported pressure-induced Fermi resonance between the fundamental modes in 7,7,8,8-tetracyanoquinodimethane. The relationship of Fermi resonance parameters (intensity ratio, coupling coefficient, frequency separation, and frequency separation of unperturbed transitions) with pressure was discussed.…”