Tandem CQDs loaded triple metal oxide interface-reinforced built-in electric field for a wide-spectral-responsive photocatalyst

Abstract

Focusing at efficient Cefixime (CEFX) removal, a delicate ultrathin-Bi2WO6 (UBWO) stacked quasi-CoFe2O4 binanosheets (BT) were meticulously designed and integrated with spherical MnWO4 (MWO) and carbon quantum dots (CQDs), forming a n-p-n CQDs@MWO/CFO:UBWO nanohybrid. XRD, XPS, TEM and other systematic analysis demonstrated the vertically aligned layer by layer assembly of UBWO:CFO BT, and a shift in the highly exposed (211) facet of UBWO after nanohybrid formation as well as large surface area (323.33 m2/g) was achieved. UV–vis DRS, PL and EIS proved high separation efficiency, prolonged life time and photogeneration of more charge carriers with absorption of full light spectrum. As expected, the optimized 5 %CQDs@0.25MWO/0.1CFO:UBWO nanohybrid displayed excellent visible light absorption and outstanding CEFX photodegradation whose kinetic constant were 21.11, 12.5, 8.82 folds higher than UBWO, CFO and MWO counterparts. This enhanced photodegradation performance ascribed to the dual strategy as follows: (i) Cascaded charge transfer with the Built-in electric field (BIEF) after n-p-n heterojunction, (ii) the upconverted PL and the electron reservoir properties of CQDs. Degradation efficiency maintained over six consecutive cycles affirming the superior recyclability of the photocatalyst. A possible degradation pathway was proposed based on GC-MS/MS analysis and the end products toxicity were systematically predicted using ECOSAR program. The toxicity of the end product was investigated against bacterial species. The proposed work provides a novel way for the fabrication of efficient photocatalyst with excellent practical applicability.