Mesoporous zirconia-ceria for anodes of SOFC and catalyzer

Full text: The ceria (CeO₂) and zirconia (ZrO₂) based materials are present in several technological applications, mainly as Solid Oxide Fuel Cells (SOFC) anodes and catalysts, for hydrogen production and automotive converter (Three-Way Catalysis). The solid solution Zr_xCe_1-xO_2-δ has attracted special attention, since it shows better thermal stability and higher oxygen storage capacity (OSC), if compared to the non-doped oxides. The mesoporous materials (pores of 2 to 50 nm) show high surface area and gas permeability, important properties for SOFCs and catalysts efficiency. In this work, mesoporous ceria-zirconia (Zr_0.1Ce_0.9O_2-δ) was synthesized by a sol-gel route using inorganic chlorides (ZrCl₄ e CeCl_3.7H₂O) as precursors, block copolymer P123 (PEO₂₀PPO₇₀PEO₂₀) as template and TIPB (triisopropyl- benzene) as swelling agent. The solution was submitted to hydrothermal treatment for 48h at 80°C and calcined at 400°C to remove the template, resulting in the crystallized oxide. The characterization was performed by X-ray diffraction at high angles (XRD), small angle X-ray scattering (SAXS), nitrogen adsorption isotherms (NAI) and transmission and scanning electron microscopy (TEM and SEM). The results showed that the material has high surface area (≈ 110 m²g^-1), a wide pore size distribution with mean values around 30 nm, predominant cubic phase Fm3m and, in less quantity, tetragonal P4₂/nmc. The micrographs revealed that the oxide is totally nano-crystallized, having pores with slit shape and a secondary smaller mesoporosity with a narrow size distribution. The amount of P123 in the synthesis was also varied in order to produce pores with different shapes. Four samples were produced with different TIPB/P123 mass rate (0, 1, 2, 4), therefore was possible to verify the pore size expansion due to the swelling addition. The structural and morphological properties remained unchanged, even with different quantities of TIPB. (author)