Dark Photocatalysis via Long-Term Storage of Photoinduced Electrons in Black-TiO x /Ag 0 Heterojunctions

Dark photocatalysts allow storage of photogenerated electrons and their post-irradiation use under no-light conditions. This requires the development of materials able to perform photogeneration of electrons, long-term in situ charge storage, and controlled transfer to acceptors on demand. Herein, we present Black-TiOx/Ag0 nanohybrids consisting of Black-TiOx decorated with plasmonic Ag0 nanoparticles produced by flame spray pyrolysis (FSP). A library of Black-TiOx/Ag0 nanocomposites was engineered, with precise control over Ag0 loading and Black-TiOx particle size. Under dark photocatalysis conditions, pre-irradiated Black-TiOx/Ag0 exhibits significant capacity to store and transfer electrons to Cr6+ or Cu2+ ions under dark conditions. Specifically, pre-irradiated Black-TiOx/Ag0 provides 0. 6 × and 2. 3 × 1021 electrons g−1 of Black-TiOx/Ag0 to Cr6+ ions and Cu2+ ions, respectively, for at least 120 min. Operando electron paramagnetic resonance (EPR) spectroscopy reveals that Magnéli -TiOx surface sites on Black-TiOx/Ag0 act as efficient trap/store units of the photoexcited electrons. The interfacial Magnéli islands introduce sub-gap energy states in TiO2, drastically improving both electron storage and visible-light activity compared to conventional TiO2/Ag0. Photoluminescence and photoelectrochemical analyses show that Black-TiOx/Ag0 exhibits high electron mobility and low hole/electron recombination rates. This analysis reveals that the interfacial Magnéli islands in contact with Ag0 act i as efficient electron storage pools of surface electrons under sunlight and ii as long-lived electron donors in the dark. This work provides a first proof-of-concept for Black-TiOx/Ag0 nanocomposites as photochargeable battery-like materials, enabling decoupled dark redox chemistry, while highlighting FSP as a versatile and scalable route for their synthesis.