Promoting photo-Fenton catalytic performance of MnFeO3-type perovskite via creation of type-II heterojunction with superior charge separator boron nitride quantum dots

Facile fabrication of Ag decorated MnFeO3 catalyst: Comparative analysis of visible light driven antibiotic reduction and antibacterial performance

Photocatalysis is an effective method with the potential to eliminate pharmaceutical compounds from water sources. Manganese ferrite (MnFeO3), a type of multiferroic perovskite catalyst, has attracted significant attention due to its small band gap, however its application was limited due to its high recombination rate and low quantum efficiency. It was therefore aimed to improve the properties of MnFeO3 by doping silver (Ag)-particles. In this study, Ag-MnFeO3 photocatalysts with different Ag content (1-3 mmol%) were synthesized by performing a facile hydrothermal method. The as-prepared samples were characterized using x-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectroscopy (DRS), photoluminescence spectroscopy (PL), electrochemical impedance spectroscopy (EIS) and Brunauer-Emmett-Teller (BET) method, showing successful addition of Ag-particles with the MnFeO3 structure. Then, the as-synthesized materials were investigated as: (i) photocatalysts for degradation tetracycline (TC) antibiotic and (ii) antibacterial agents for bacteria. The Ag-MnFeO3 catalyst demonstrated superior catalytic performance (95.7%), which was 1.6 times higher than that of pristine MnFeO3 (59.7%). The positive effect was ascribed to oxygen vacancies, enhanced light absorption ability, and lower recombination rate. The Ag-MnFeO3 catalyst also showed satisfactory removal performances in real water matrices. Furthermore, radical trapping tests depicted that the superoxide radicals played a dominant role in the photodegradation system. In addition, Box-Behnken design (BBD) was performed to determine the optimum conditions, which were determined as catalyst dosage of 0.45 g/L, initial TC concentration of 5.10 mg/L, and initial solution pH value of 3.69. In terms of antibacterial tests, the incorporation of Ag into the MnFeO3 structure greatly increased the antimicrobial resistance against bacteria. Our findings disclose that the incorporation of Ag into the MnFeO3 structure can be regarded as a feasible and promising approach to improve both photocatalytic degradation and antibacterial performances.

Developing boron carbon nitride/boron carbon nitride-citric acid quantum dot metal-free photocatalyst and evaluating the degradation performance difference of photo-induced species for tetracycline via theoretical and experimental study

For opening a way to synthesize novel metal-free catalysts and clarifying the photodegradation performance difference of photoactive species (such as ·O₂^-, h⁺), a series of metal-free photocatalysts have been synthesized by using different existing forms of the same materials (boron carbon nitride (BCN) and boron carbon nitride-citric acid quantum dot (BCQD)) as precursors via calcinating their mixture at 350 °C. BCQD has good fluorescence and up-conversion fluorescence performance. BCN/BCQD-350 has the highest removal efficiency (90%, including adsorption 60% and photodegradation 30%) for tetracycline (TC) among all samples under visible light irradiation. TC adsorption by BCN/BCQD-350 conforms to pseudo-second-order kinetic and Langmuir isotherm models. TC photodegradation by BCN/BCQD-350 conforms to type II heterojunction mechanism. Photoactive species capture experiments suggest that·O₂^- makes a higher contribution for TC photodegradation, followed by h⁺, ·OH, ¹O₂ and e^-. From LC-MS results, TC photodegradation is initiated by the dehydration step. TC dehydration activated by ·O₂^- has the lowest barrier (43.4 kcal/mol) than that (50.1 kcal/mol) activated by h⁺, that (64.8 kcal/mol) without the activation by photoactive species. TC removal rate of BCN/BCQD-350 (0.01563 min^-1) is higher than that of g-C₃N₄, P25 (TiO₂), BNPA, BCNPA, etc. Furthermore, BCN/BCQD-350 can also photodegrade TC under infrared light irradiation (λ > 800 nm).