Novel B-site substituted KCuTa3-xNbxO9 solid solution photocatalysts with modulated band structure for visible-light-driven hydrogen evolution

Perovskite-like metal oxides (PLMOs), featuring unique structural and optical properties, exhibit great potential in photocatalytic water splitting field. However, the wide bandgap and strong carrier recombination severely suppress their photocatalytic hydrogen production activity. Thus, design and development of novel PLMO photocatalyst with extended photo-response range and enhanced photo-generated charge separation/transport efficiency remains an ongoing challenge. Herein, a series of novel B-site substituted KCuTa3-xNbxO9 solid solution photocatalysts were synthesized via a simple solid-state reaction method. With an increased content of Nb, a distinct red-shifted of the optical absorption edge of KCuTa3-xNbxO9 solid solution was observed, leading to a decreased bandgap (from 2.69 to 1.91 eV), and a positive shift of the conduction band bottom (from −0.54 to −0.49 eV vs RHE). All of the Nb-substituted KCuTa3O9 solid solutions exhibit enhanced separation efficiency of photoinduced charge carriers, which leads to increased hydrogen evolution activity, among which KCuTa0.75Nb2.25O9 exhibits the highest hydrogen evolution rate of 2.16 μmol h−1 under the visible light irradiation (λ > 420 nm), which is approximately 7-fold higher than that of the pure KCuTa3O9. This study demonstrates the potential of modulating band structure through constructing solid solutions for efficient perovskite-like metal oxides photocatalysis.