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Harnessing the synergistic dual role of lignin-derived blue carbon dots over TiO2 for highly efficient solar photocatalytic degradation of tetracycline
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DOI：10.1039/D6NJ00560H.png)
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Abstract
En 中文
Titanium dioxide (TiO2) possesses a relatively wide bandgap; which limits its light absorption predominantly to the ultraviolet region; leading to low utilization efficiency of the broader solar spectrum. To enhance the solar energy harvesting capability of TiO2; lignin-derived blue carbon dots (BCDs) were employed as bifunctional promoters. The synthesized BCDs exhibit an average diameter of approximately 2.8 nm; abundant surface functional groups; a fluorescence lifetime of 8.56 ns; and a quantum yield of 4.96%. Compared to pristine TiO2; the BCDs/TiO2 composite demonstrates a narrowed bandgap of 2.99 eV and an extended photoresponse into the visible region up to 414 nm. Photoelectrochemical measurements further reveal that the formation of a type-II heterojunction enhances the photocurrent density from 1.0 µA cm−2 to 2.5 µA cm−2; representing a 150% improvement in charge separation efficiency. Photocatalytic evaluation shows superior performance of the composite; achieving a 98.6% degradation rate of tetracycline (TC) within 120 min; with an apparent rate constant (0.0260 min−1) approximately 16 times higher than that of pure TiO2. Furthermore; the composite exhibits excellent stability and reusability; retaining over 85.7% of its initial efficiency after five consecutive cycles. Mechanistic studies based on energy-band structure analysis and active species trapping experiments indicate that the bifunctional BCDs serve as photosensitizers to inject electrons into the conduction band of TiO2; and simultaneously form a type-II heterojunction with TiO2 to facilitate hole transfer. This synergy greatly enhances the separation efficiency of photogenerated charge carriers; with holes (h+) and superoxide radicals (˙O2−) identified as the primary active species in the TC degradation process. Analysis of the multi-pathway degradation process further confirms that the photocatalytic system follows a reactive oxygen species (ROS)-driven advanced oxidation mechanism.
Keywords:
lignin-derived blue carbon dots
TiO2
photocatalysis
tetracycline degradation
type-II heterojunction
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