Unravelling charge carrier separation mechanism in Ag/β-BaTi ₂ O ₅ heterostructures for high-efficiency photocatalysis: a synergistic study combining Kelvin probe force microscopy and density functional theory

The sustainable treatment of industrial organic wastewater remains challenging due to the stabilization and aromatic structures against conventional degradation pathways. Herein, we report a facile solvothermal synthesis of Ag/β-BaTi₂O₅ heterostructures and systematically investigate, for the first time, the impact of Ag loading on the properties of the novel β-BaTi₂O₅ photocatalyst. Experimental and theoretical analyses reveal that Ag nanoparticles act as electron traps, forming a Schottky barrier at the β-BaTi₂O₅ interface, which significantly suppresses charge recombination and narrows the band gap (from 3.20 eV to 2.77 eV). The optimized 5-Ag/β-BaTi₂O₅ sample achieves 98% degradation of methylene blue under ultraviolet light within 80 min, exhibiting a kinetic constant (0.0415 min^-1) 2.3 times higher than that of pristine β-BaTi₂O₅ nanorods. Kelvin probe force microscopy and density functional theory calculations verify the interfacial electron transfer from β-BaTi₂O₅ nanorods to Ag nanoparticles driven by the built-in electric field under illumination. The catalyst also demonstrates excellent cycling stability (∼86% efficiency after 6 cycles) and degradation versatility towards Rhodamine B, tetracycline, and levofloxacin. This work provides in-depth mechanistic insights for sustainable wastewater treatment using noble metal-modified Ba-Ti-based photocatalysts.