One-Dimensional CaNbO ₂ N Single Crystals with Low Defect Densities for Photocatalytic Water Splitting in the Presence of Sacrificial Reagents

A large number of defects and insufficient active sites are two important factors resulting in the poor photocatalytic activity of CaNbO₂N. In this work, we successfully prepared one-dimensional (1D) single-crystal CaNbO₂N (CNON-P) with highly crystallinity based on a chemical vapor deposition-re-evaporation strategy (Bi₂O₃ as the evaporation source). The strategy effectively suppressed the generation of defects, achieved spatial separation of the active facets, and increased active sites, promoting carrier separation and transfer. This strategy unexpectedly enhanced the hydrophilicity as well, facilitating intimate contact between the photocatalyst and water. Compared to the 1D CaNbO₂N without using the chemical vapor deposition-re-evaporation strategy and the conventional CaNbO₂N prepared by thermal ammonolysis of oxide particles, the photocatalytic performance of the CNON-P was significantly enhanced due to the coupling of these favorable factors. Its H₂ and O₂ production rates in the presence of sacrificial reagents reached 55.0 μmol h^-1 and 11.7 μmol h^-1 under visible-light (λ ≥ 420 nm) irradiation, respectively, with the H₂ production rate being the highest reported for CaNbO₂N so far. It is hoped that this work can provide a new pathway for defect control of different perovskite oxynitrides.