Oxygen Vacancy-Driven Dual-Site Pd-TiO₂ Sonocatalyst for Amplified Reactive Oxygen Species Generation and...

Ultrasound (US)-triggered reactive oxygen species (ROS) generation by nano-sonocatalysts is vital for sonocatalytic therapy. However, the therapeutic effect is hindered by the low ROS generation yield owing to sluggish charge transfer and elusive active sites. Herein, in situ oxygen vacancies (Vo)-engineered Pd-TiO₂ sonocatalysts with spatially separated dual reactive sites are developed, which optimize charge kinetics and amplify ROS generation. Mechanism studies revealed that US-induced Vo serves as an electron pump, activating the Pd-O-Ti transport channel, lowering interfacial barriers and steering electron migration from TiO₂ to Pd. This ordered charge redistribution tunes the d-band center of Pd, designating electron-rich Pd sites as the primary active center for O₂ adsorption and activation to produce singlet oxygen (¹O₂). Concurrently, Vo-mediated reconstruction of Ti 3d states strengthens orbital coupling with H₂O at the Pd-O-Ti interface, dominating the activation of H₂O to promote the generation of hydroxyl radical (•OH). This dual-site configuration effectively lowers the activation energy barriers, which increases the rate constants of ¹O₂ and •OH generation by 5.0-fold and 2.7-fold, respectively, and ultimately achieving an 87.5% tumor inhibition efficiency. This work provides molecular insights into the charge transfer cascade and critical active centers in US-activated Pd-TiO₂, offering a rational paradigm for designing high-performance sonocatalysts.