A novel contractive effect of KTaO₃ nanocrystals via La³⁺ doping and an enhanced photocatalytic performance

Graphical abstract: The incorporation of La³⁺ ions in KTaO₃ host lattice led to a monotonous lattice contraction and particle size reduction, showing an excellent photocatalytic performance. - Highlights: • La³⁺ incorporation in KTaO₃ led to a lattice contraction, particle size reduction. • Oxidative capacity of the photo-excited carriers increases after La³⁺ ions doping. • Ta⁴⁺ appearance was helpful for the separation of electron-hole pairs. • Photocatalytic performance of K_1−xLa_xTaO₃ optimized by La³⁺ doping. - Abstract: La³⁺-doped cubic potassium tantalate photocatalysts were prepared by a hydrothermal treatment process. It is found that the La³⁺ ions were homogeneously incorporated in the KTaO₃ host lattice, leading to a monotonous lattice contraction and particle size reduction. Meanwhile, the BET surface areas were also enlarged from 4.9 to ∼9.8 m² g⁻¹. Consistently, La³⁺-doped KTaO₃ nanocrystals showed a broadened band gap, which can be well-defined as a consequence of the contractive particle size. DFT calculation predicted a deeper band edge and a dispersive dense state of valance state by La³⁺ ions doping due to the hybridization of O 2p and La 6p orbitals, increasing the oxidative capacity and mobility of photogenerated charge carriers, thus enhance the photocatalytic activity. The mixed state of Ta⁵⁺ and Ta⁴⁺ was found to appear in the K_1−xLa_xTaO₃ nanocrystals, which may suppress the formation of cationic vacancies. The superior photocatalytic performance of K_1−xLa_xTaO₃ nanocrystals was achieved by well-controlled contractive particle size and optimized La³⁺ doping level