  High-entropy oxides (HEOs), as multi-component ceramics with high
configurational entropy, have been of recent interest due to their attractive
properties including photocatalytic activity for H2 production and CO2
conversion. However, the photocatalytic activity of HEOs is still limited to
ultraviolet light. In this study, to achieve visible-light-driven
photocatalysis, 10 different heterojunctions were simultaneously introduced in
the Ti-Zr-Nb-Ta-W-O system. The oxide, which was synthesized by a high-pressure
torsion method and oxidation, successfully produced oxygen from water under
visible light without co-catalyst addition. The photocatalytic performance was
attributed to high visible-light absorption, narrow bandgap, appropriate band
structure, presence of multiple heterojunctions and accordingly easy
electron-hole separation and slow recombination. These results not only show
the potential of high-entropy oxides as new visible-light-active
photocatalysts, but also introduce the multiple-heterojunction introduction as
a strategy to achieve photocatalysis under visible light.
