Oxygen Vacancy-Engineered Cd_1-x Ag _x O_1-y Nanostructures for Visible-Light-Driven Hazardous Dye Remediation

Addressing the intertwined challenges of sustainable wastewater remediation and the development of efficient heterogeneous photocatalysts for visible-light applications remains a pivotal objective in environmental nanotechnology. This study presents the rational design and development of oxygen-vacancy-engineered Cd_1-x Ag _x O_1-y nanostructures as next-generation visible-light-active photocatalysts for environmental remediation. The incorporation of Ag dopants in a CdO matrix not only modulates the lattice architecture but also promotes the formation of electronically active oxygen vacancies, thereby enhancing the material's optoelectronic properties. Detailed structural and spectroscopic investigations confirm that 3 wt % Ag doping induces lattice strain, narrows the bandgap, and introduces midgap states conducive to visible-light absorption and prolonged charge carrier lifetimes. These tailored features culminate in superior photocatalytic degradation of Amido Black 10B dye, achieving 91% removal within 24 min under 450 nm LED illumination, adhering to zero-order kinetics and yielding a high apparent quantum yield of 27.5%. Mechanistic insights derived from scavenger assays and ESR spectroscopy reveal that superoxide radicals (O₂ ^•-) are the principal reactive species driving oxidative degradation. Electrochemical analyses, including Mott-Schottky profiling and impedance spectroscopy, further substantiate the enhanced charge separation, elevated carrier density, and favorable energy band alignment induced by Ag doping and oxygen vacancy generation. The photocatalyst exhibits robust operational durability over five cycles without structural compromise or significant metal leaching. Phytotoxicity evaluation via chickpea (Cicer arietinum L.) germination assays confirms the nontoxic nature of the treated effluent, underscoring its environmental compatibility. Collectively, this work advances Cd_1-x Ag _x O_1-y as a high-efficiency, defect-engineered photocatalyst with significant promise for sustainable, real-world wastewater remediation under ambient visible-light conditions.