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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>⋅</mml:mo> <mml:msubsup><mml:mrow><mml:mi>O</mml:mi></mml:mrow> <mml:mrow><mml:mn>2</mml:mn></mml:mrow> <mml:mrow><mml:mo>-</mml:mo></mml:mrow> </mml:msubsup> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts><mml:mrow><mml:mi>O</mml:mi></mml:mrow> <mml:mrow><mml:mn>2</mml:mn></mml:mrow> <mml:none></mml:none> <mml:mprescripts></mml:mprescripts> <mml:none></mml:none> <mml:mrow><mml:mn>1</mml:mn></mml:mrow> </mml:mmultiscripts> </mml:math> , 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.