Ceria−Zirconia Solid Solutions (Ce_(1−x)Zr_xO_(2−δ), x ≤ 0.2) for Solar Thermochemical Water Splitting: A Thermodynamic Study

The redox behavior of ceria–zirconia solid solutions (or Zr-substituted ceria, ZSC) with a Zr content of up to 20 mol % is studied by thermogravimetry (TG) between 600 °C and 1490 °C under controlled atmospheres. Thermodynamic properties, specifically standard oxidation enthalpy, ΔH_(oxd)^⊖, and entropy, ΔS_(oxd)^⊖, are derived from TG data. The raw TG results show that the extent of reduction is significantly increased (compared with undoped ceria), even at a low Zr substitution level of 5 mol %. Concomitantly, the magnitude of the thermodynamic functions dramatically decreases as a function of Zr content, particularly at low values of oxygen non-stoichiometry, δ (