HIGH-ENTROPY OXIDES - PROMISING MULTIFUNCTIONAL MATERIALS

Abstract

A new class of materials with enhanced physical and chemical properties and high potential application are multi-component oxides or high-entropy oxides (HEOs). These entropy-stabilized oxides mostly comprise five or more elemental components in an equimolar ratio, incorporated within a single-phase system. The thermodynamic contribution of configurational entropy in the system of minimally five different components is sufficient to overcome the enthalpy of formation and reduce the Gibbs free energy. In this talk, I will present the potential of nanostructured high–entropy oxides (HEOs) for photocatalytic CO₂ hydrogenation, a process with significant implications for environmental sustainability and energy production. Several cerium–oxide–based rare–earth HEOs with fluorite structures were prepared for UV–light driven photocatalytic CO₂ hydrogenation towards valuable fuels and petrochemical precursors. The cationic composition profoundly influences the selectivity and activity of the HEOs, where the Ce_0.2Zr_0.2La_0.2Nd_0.2Sm_0.2O_2–δ catalyst showed outstanding CO₂ activation (14.4 mol CO kgcat⁻¹ h⁻¹ and 1.27 mol CH₃OH kgcat⁻¹h⁻¹) and high methanol and CO selectivity (7.84 % CH₃OH and 89.26 % CO) at ambient conditions with 4–times better performance in comparison to pristine CeO₂. The observed formate–routed mechanism and a surface with high affinity to CO₂ reduction offer insights into the photocatalytic enhancement (Šarić et al. 2025; Tatar et al. 2024).