What question did this study set out to answer?

To explore how different cation ratios in Co/Fe layered double hydroxides affect their synthesis and properties.

February 26, 2026Open Access

Fine Characterization of Co/Fe-Based Materials: Insights into the Influence of Cation Ratios Between 2/2 and 10/2 on Obtaining Layered Double Hydroxides

Key Points

To explore how different cation ratios in Co/Fe layered double hydroxides affect their synthesis and properties.
Synthesis of Co/Fe LDH materials with cation ratios from 2/2 to 10/2 under controlled pH conditions (8 or 11.5)
Characterization using multiscale techniques like FTIR, SEM, TEM-EELS, XRD, and TGA
Assessment of mineralogical phases and chemical composition through local analyses like EDX.
Synthesis yielded well-crystallized LDHs for ratios 4/2 and 6/2, with purity of 95–98% for certain phases
pH 8.0 resulted in quasi-hexagonal particles sized 200 to 500 nm
For 2/2 ratios, 97% mass fraction of products was achieved, while 10/2 ratio showed partial Co precipitation.

Abstract

Co/Fe layered double hydroxides (LDHs) are among the most promising materials for advanced industrial and energy applications. Controlling the synthesis conditions of LDH materials is thus crucial to precisely tailoring cation composition and distribution, thereby regulating surface charge, ion sorption, and electron transfer required for optimal chemical and electrochemical performance. Therefore, characterizing Co/Fe precipitates (chemical composition, purity, morphology, and crystallinity) is also required to further exploit their controlled properties. Thus, solids with Co/Fe cation ratios between 2/2 and 10/2 were synthesized under an air atmosphere, at pH 8 or 11.5. For the first time, multiscale physicochemical techniques (FTIR, TEM-EELS, SEM, AAS, TGA, CHN elemental analysis, and XRD complemented by Rietveld refinement) were used to provide a fully documented characterization of the structure, texture, purity, chemical composition, and thermal properties of Co/Fe LDH-based materials. The combined interpretation of data from these complementary techniques enabled the precise identification and chemical characterization of the mineralogical phases formed. Both acid–base and redox reactions govern the overall CoII/FeIII LDH formation process. Well-crystallized LDHs were synthesized, except for the 2/2 ratio at pH 11.5, which led to the formation of α-Co(OH)2, γ-Fe2O3, and Co3O4 byproducts. A pH value of 8.0 provides valuable LDH materials made of quasi-hexagonal particles with diagonal lengths between 200 and 500 nm. Rietveld refining showed the presence of LDH phases in the range of 95–98%. Multiple local chemical analyses using EDX on chosen particles demonstrated pure 4/2 and 6/2 LDHs. For the 2/2 ratio, the cumulative mass fraction of two LDH-type products consistently reached 97%, distributed between Co/Fe 1.5/2 (71%) and Co/Fe 4/2 (29%). For the 10/2 ratio, only partial Co precipitation was observed, forming 95% Co/Fe LDH phases distributed between Co/Fe 10/2 (72%) and 7/2 (28%).

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Cite This Study

Khalil et al. (Tue,) studied this question.

synapsesocial.com/papers/699fe35995ddcd3a253e72ef https://doi.org/https://doi.org/10.3390/ma19050838

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