Investigation of a high-entropy oxide photocatalyst for hydrogen generation by first-principles calculations coupled with experiments: Significance of electronegativity

Abstract: 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.