Thermal Behavior, Phase Composition, and Surface Chemistry of a Multiphase Cₓ–NaOₓ–La–O–CeO₂ Hybrid Material

This study reports the synthesis and physicochemical characterization of a hybrid material composed of a carbonaceous matrix modified with lanthanum (La), cerium (Ce), and sodium (Na), designated Sample B. Thermoanalytical techniques, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were combined to examine its thermal behavior, phase composition, and surface chemical environments. The study is limited to material characterization and does not evaluate catalytic, chemical-sensing, electrical, or electrochemical performance.
Thermogravimetric (TG–DTG) and differential thermal analysis (DTA) revealed multistep behavior. Moisture and weakly retained species were removed at low temperature, while a broad exothermic event with a maximum at 469.6 °C was attributed predominantly to oxidation of the carbonaceous matrix, with possible overlapping decomposition and reorganization of the inorganic components. DTA alone does not demonstrate crystallization of CeO₂, La₂O₃, or another specific phase. XRD supported the coexistence of a low-order carbonaceous matrix with crystalline CeO₂ domains; La₂O₃ and Na₂CO₃ were considered probable, whereas La(OH)₃ remained provisional because of reflection overlap.
XPS qualitatively confirmed C, O, Na, La, and Ce at the surface. The corrected C 1s contributions at 284.80, 286.18, and 291.06 eV were compatible with C–C/C=C, overlapping C–O/C–OH/C–O–C environments, and a π–π* shake-up satellite, respectively. The O 1s contribution at 532.73 eV was treated as an overlapping oxygenated envelope, whereas the component at 537.23 eV remained unresolved and was not assigned to a specific species. Na 1s confirmed sodium in oxygen-containing environments without differentiating NaOH, Na₂CO₃, Na₂O-like species, or possible interfacial configurations. La 3d was compatible with La³⁺–O environments, and Ce 3d qualitatively confirmed oxidized cerium; however, the available resolution did not permit reliable differentiation of individual La species, quantification of Ce³⁺/Ce⁴⁺, or determination of oxygen-vacancy concentration.
The combined results support a heterogeneous, multiphase structural model comprising a functionalized low-order carbon matrix, crystalline CeO₂ domains, La–O species, and probably partially carbonated sodium species. These findings establish the material’s thermal, structural, and surface-chemical characteristics. Possible catalytic, adsorption, sensing, or electrochemical behavior remains unverified and requires dedicated functional tests, suitable control materials, quantitative composition analysis, and complementary textural, morphological, spectroscopic, and electrical measurements.

activated carbon; ceria; lanthanum oxide; sodium species; thermal analysis; X-ray diffraction; XPS; hybrid material.

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