  High-entropy oxides (HEOs), containing at least five principal cations, have
recently emerged as promising photocatalysts for hydrogen production via water
splitting. Despite their high potential, the impact of the cation mixtures on
photocatalytic activity remains poorly understood. This study investigates the
high-entropy photocatalyst TiZrHfNbTaO11 using first-principles calculations
combined with experimental methods to elucidate the effects of various elements
on electronic structure and water splitting performance. The results indicate
that the HEO exhibits a bandgap comparable to TiO2 polymorphs rutile, brookite
and anatase. Cations with lower electronegativity, such as hafnium and
zirconium, provide the strongest water adsorption energy, serving as active
sites for water adsorption. Additionally, the co-presence of highly
electronegative cations like niobium and tantalum adjacent to hafnium and
zirconium enhances charge transfer to water molecules, improving splitting
efficiency. These findings suggest novel strategies for designing high-entropy
photocatalysts by synergistic incorporating cations with different
electronegativities.
