Region-specific defect engineering of Bi2W1-xO6-γ induces nanoscale electric fields and surface active-sites for enhanced visible-light oxidation of salt-lake flotation agents.

Breaking the limitations of conventional defect engineering, this work pioneers region-specific dual-defect engineering in Bi2WO6. By precisely tailoring tungsten (W) and oxygen (O) vacancies at nanoscale spatial domains-W vacancies at the edges and O vacancies at the center-a spatially asymmetric defect configuration is achieved. This configuration induces a synergistic "defect dipole" effect, amplifying the internal electric field by 2.74 times while simultaneously enriching surface-active sites. As a result, the photocatalytic efficiency is dramatically enhanced, achieving complete oxidation of recalcitrant flotation agents-octadecylamine (ODA) and 4-dodecylmorpholine (DMP)-within just 2 h of visible light irradiation, which is 3.6 times faster than that of pristine Bi2WO6. Additionally, the generation of reactive species ( ⋅ O 2 - , O 2 1 , and h⁺) is significantly boosted by factors of 8.98, 5.55, and 20.02, respectively, highlighting the material's remarkable reactivity. Photoelectrochemical analyses reveal a remarkable 290% increase in charge separation efficiency. This enhancement is further supported by an improved O2 adsorption capacity, which promotes the formation of reactive oxygen species involved in the degradation process. Impressively, the engineered Bi₂W₁₋ₓO₆₋ᵧ exhibits outstanding performance in real-world industrial wastewater treatment under solar irradiation, demonstrating its practical viability. Overall, this work establishes a new paradigm in photocatalysis by integrating precise nanoscale defect engineering with enhanced electrostatic modulation.