Foam-like Ce–Fe–O-based nanocomposites as catalytic platforms for efficient hydrogen oxidation in air

Foam-like nanocomposites of the Ce–Fe–O system with two (c-CeO₂, am-F₂O₃), three (c-CeO₂, o-CeFeO₃, α-F₂O₃), or four phases (c-CeO₂, o-CeFeO₃, α-F₂O₃, am-Fe₂O₃) were synthesized using the RedOx reaction of glycine-nitrate combustion. The glycine/nitrate ratio (G/N) varied from deficient (0.2, 0.4) and stoichiometric (0.6) to excess ratios of glycine (0.8, 1.0, 1.2, 1.4). PXRD, ⁵⁷Fe Mössbauer spectroscopy, N₂-physisorption, TEM, H₂-TPD, O₂-TPD, and H₂-TPR were used to examine the characteristics of the obtained samples. The average crystallite size of the obtained composites was in the range of 1.3–31.3 nm, 33.4–50.7 nm, and 10.1–33.9 nm for c-CeO₂, o-CeFeO₃, and α-Fe₂O₃, respectively. The lowest S_BET (1.5 m²/g) belonged to the case of stoichiometric G/N, while the highest value (49.2 m²/g) was found in the case of the highest amount of glycine (G/N = 1.4); the latter case also had the largest total pore volume (V_p = 0.182 cm³/g) when compared to the others. Moreover, the advanced catalytic performance of foamy Ce–Fe–O-based nanocomposites toward H₂ combustion in air was found with t₁₀ = 275 °C, t₅₀ = 345 °C, and E_a = 76.9 kJ/mol for sample G/N = 1.2. The higher activity of sample G/N = 1.2 in catalysis was attributed to different properties of the composite, including an appropriate component phase ratio, the smaller size of crystallites, higher specific surface area, higher reducibility,oxygen capacity, etc. The findings make it possible to carry out the directed synthesis of catalysts based on the Ce–Fe–O system with specific phases, dispersion, and morphological composition for efficient hydrogen oxidation at moderate temperatures.