Single-Atom Photocatalyst as Floatable Artificial Leaf for Upcycling Oceanic Plastic Waste

Over ∼8 billion tons of plastic have been produced to date, with ∼80% of them ended up in landfills/oceans. Among them, polypropylene (PP) possesses the lowest global recycling rate (< 1%). To resolve this, Ru single atoms (SAs) loaded photocatalysts (ZnIn₂S₄/Ru SAs) in the forms of powder/floatable artificial leaf (AL) were prepared for direct conversion of raw PP plastic into valuable chemicals. The optimized photocatalyst exhibits exceptional performance with a total formic/acetic acid production of 1022.5 µmol g⁻¹. In situ X-ray photoelectron spectroscopy, in situ atomic force microscopy-kelvin probe force microscopy, and in situ electron paramagnetic resonance (EPR) reveal efficient electron extraction from ZnIn₂S₄ nanosheets to Ru SAs, with subsequent electron capture by O₂ molecules in air. Additionally, in situ transient-state photoluminescence spectroscopy, transient photovoltage measurement, and in situ EPR unveil the electrolyte-assisted polarization (induced by cations/anions in seawater) significantly enhancing charge separation/transfer. Finally, in situ EPR, in situ infrared (IR) spectroscopy, and quenching experiments corroborate the pivotal roles of reactive oxygen species (·O₂⁻/·OH) for upcycling PP into valuable chemicals. These results highlight the transformative potential of floatable AL concept for converting plastic waste into high-value chemicals, offering a sustainable solution to plastic contamination.