Preparation of phosphorus-modified BiO_x as versatile catalyst for enhanced photo-reduction of Cr(VI) and oxidation of organic dyes

The high-performance photocatalysts have received considerable attention in the field of environmental remediation. Herein, the synthesis of multi-phase BiO_x nanocrystals decorated by phosphorus dopant is reported through a facile one-pot solvothermal method. The resulting P_0.15BiO_x photocatalyst exhibited an optimal Cr (VI) reduction and RhB oxidation rates of 84% and 96% under visible light irradiation, being nearly 2 times higher than that of pristine BiO_x sample. The improved photocatalytic performance could be ascribed to the synergetic effects of well-matched band positions via formation of new electron evolution pathway, efficient charge carrier mobility and introducing electronic defects by insertion of P⁵⁺ ions into the structure. Furthermore, DFT presented formation of mid-gap hybrid of p states, which enhanced the light absorption capacity. The photocatalytic mechanism revealed the photogenerated holes were dominant. Moreover, the P_0.15BiO_x had quite stable crystal structure and recycling ability. In this work, we obtained a single metal oxide with polycrystalline nature which obtains better charge separation compared to the pure phases, leading to capability of the photocatalyst for both photo-oxidation and photo-reduction processes. The present study provides new insights into the design of atomic-level structural defects in the photocatalysts by a facile method, for efficient removal of heavy metal ions and dyes from the wastewater.