Hybrid d0 and d10 electronic configurations promote photocatalytic activity of high-entropy oxides for CO2 conversion and water splitting

Abstract

Photocatalysis offers a sustainable solution for essential reactions such as CO₂ conversion and water splitting, but constraints in catalyst properties like bandgap and active site availability often limit its efficiency. High-entropy oxides (HEOs), which incorporate five or more different cations, present significant potential for this application due to their elemental diversity. This study explores active HEO development for photocatalytic applications by integrating cations with d⁰ and d¹⁰ electronic configurations. A single-phase HEO with a monoclinic structure was successfully synthesized, comprising elements with d⁰ (titanium, zirconium, niobium and tantalum) and d¹⁰ (zinc) electronic configurations. Comprehensive analyses of its microstructure, chemical composition, optical properties and photocatalytic activity were conducted. The resulting TiZrNbTaZnO₁₀ exhibited superior UV and visible light absorption, a low bandgap of 2.5 eV, minimal radiative electron–hole recombination and high stability under photocatalytic conditions. Remarkably, TiZrNbTaZnO₁₀ outperformed the TiZrHfNbTaO₁₁ photocatalyst which contains solely d⁰ electronic configuration. This enhanced performance is attributed to the mixed electronic configurations fostering heterogeneous chemical environments, which facilitate efficient charge carrier separation and transfer.