Defective high-entropy oxide photocatalyst with high activity for CO₂ conversion

High-entropy oxides (HEOs), as a new family of materials with five or more principal cations, have shown promising properties for various applications. In this work and inspired by inherent defective and strained structure of HEOs, photocatalytic CO₂ conversion is examined on a dual-phase TiZrNbHfTaO₁₁ synthesized by a two-step high-pressure torsion mechanical alloying and high-temperature oxidation. The HEO, which had various structural defects, showed simultaneous photocatalytic activity for CO₂ to CO and H₂O to H₂ conversion without the addition of a co-catalyst. The photocatalytic activity of this HEO for CO₂ conversion was better than conventional photocatalysts such as anatase TiO₂ and BiVO₄ and similar to P25 TiO₂. The high activity of HEO was discussed in terms of lattice defects, lattice strain, light absorbance, band structure, photocurrent generation and charge carrier mobility to activation centers. The current study confirms the high potential of HEOs as a new family of photocatalysts for CO₂ conversion.