Post-COVID-19, two big environmental problems stand out: piles of waste medical masks and non-degradable microplastics, with existing methods like incineration being inefficient. Researchers from Zhejiang Normal University found a solution—they turned waste masks into blue-fluorescent carbon quantum dots (MCQDs) via a simple solvothermal process, then doped MCQDs into BiOBr/g-C₃N₄ to build an S-scheme heterojunction photocatalyst to degrade microplastics. DFT calculations confirmed an interfacial electric field in the heterojunction, while radical capture experiments identified ·O₂⁻ and h⁺ as key active species.
The optimized BiOBr/g-C₃N₄/3MCQDs degraded 39.88%±1.04% of PET in seawater—where Cl⁻ enhanced performance by exposing active sites—1.37 times more effective than BiOBr/g-C₃N₄ and better than most reported catalysts. It’s stable (over 90% efficiency after 5 cycles), and PET degradation products (e.g., ethylene glycol, benzoic acid) can be used for polymers or drugs.
The work titled “Waste medical mask-derived carbon quantum dots enhance the photocatalytic degradation of polyethylene terephthalate (PET) over BiOBr/g-C₃N₄ S-scheme heterojunction”, was published on Acta Physico-Chimica Sinica (published on July 25, 2025).
DOI:10.1016/j.actphy.2025.100135