For example, NiFe-LDH has prevalent raman peak. If NiFe-LDH go through surface partial oxidation, would the crystal remain unchanged in XRD and the raman spectrum change similar with oxyhydroxide?
Sungjun Lee
The Raman spectrum is obtained as a result of the interaction of a laser beam with the electron density of covalent bonds where the laser beam penetrates. For crystalline solids, this is usually their surface. The crystal structure is measured by wide-angle X-rays. Therefore, it may be that the characteristic absorption bands change during surface oxidation, but the diffraction pattern does not change during surface oxidation.
XRD is more sensitive to the overall crystal structure and may not detect subtle changes at the surface level.Raman spectroscopy is sensitive to changes in the molecular vibrations and bonding environment, which can be affected by surface oxidation.
If available, Raman mapping is the most appropriate technique, which can provide you both chemical and spatial information of the materials and its surface with the depth from a micron up to a few hundred microns scale, subject to the materials and experimental configuration of Raman system.
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