Tailoring Surface Charges of Bi ₄ Ti ₃ O ₁₂ via Bi ⁰ /Oxygen Vacancy Synergy for Enhanced Photocatalysis

The selective removal of trace cationic pollutants from wastewater remains a formidable challenge for conventional photocatalysts, primarily due to insufficient adsorption specificity and rapid charge carrier recombination. Herein, we report a rational surface charge engineering strategy through the synergistic implantation of metallic Bi⁰ and oxygen vacancies (Vo) into Bi₄Ti₃O₁₂ (BTO) via a molten salt method. This Bi⁰/Vos dual-site synergy profoundly enhances photocatalytic performance by concurrently broadening visible light absorption, suppressing charge recombination (9-fold increased photocurrent and prolonged carrier lifetime), and creating a selectively negative surface charge. The optimized photocatalyst Bi⁰/Vos-BTO exhibits exceptional visible light activity and remarkable selectivity for cationic dye degradation, achieving a 28-fold enhancement in the reaction rate constant and a 29-fold higher apparent degradation rate compared to pristine BTO. Mechanism investigations demonstrate that the engineered negative surface enables strong electrostatic attraction toward cationic dyes, elucidating the origin of the selectivity. Furthermore, radical trapping and spectroscopic analyses reveal that the Bi⁰/Vos synergy serves as an efficient electron reservoir and activation site, boosting O₂ activation to generate multiple reactive oxygen species (ROS). This work not only provides fundamental insights into how synergistic defects modulate surface charge distribution to govern photocatalytic selectivity but also establishes a versatile electrostatic-programmable strategy for the targeted degradation of pollutants in complex aqueous environments.