Tuning surface sites to boost photocatalytic degradation of phenol and ciprofloxacin

One-Pot Synthesis of C@BiOBr for Efficient Photocatalytic Degradation of Phenol

This work describes the synthesis of C@BiOBr using glucose as the carbon precursor by a repeatable one-step hydrothermal method. Characterization studies indicate that the structure of BiOBr did not change after the carbon layer was encapsulated on the surface. The highest activity is achieved at 1.2-C@BiOBr, with 97% of phenol (50 mg·L-1) degrading within 90 min, and the degradation amount of phenol is determined to be 48.5 mg·g-1 with a speed of 0.54 mg·g-1·min-1. The useful species of phenol degradation are studied and assigned to •O2-, 1O2, and h+. The effect of coated carbon layer for photocatalytic degradation of phenol over BiOBr is studied by photoelectrochemical experiments, fluorescence spectra, and density functional theory (DFT) calculations. It is attributed to the good conductivity of carbon, enhanced separation of the photocarriers by carbon coating, and thermodynamically favorable reactive oxygen species (ROS) production on the surface of carbon. This work demonstrates that carbon coating is an effective strategy to improve the photocatalytic activity of BiOBr and reveals the detailed mechanism.

Assembly of Functional Co(II) Metal-Organic Frameworks through a Mixed Ligand Strategy: Structure and Photocatalytic Degradation Properties

Four Co(II)-based metal-organic frameworks (MOFs) were constructed by a mixed ligand strategy under solvothermal conditions. The controllable modification of the bridging groups in the secondary building units was realized by changing the anions in MOFs 1-3. The MOF 4 with 3D framework structure was obtained by regulating the solvent ratio following the synthesis process of MOF 3. Furthermore, the MOFs 1-4 exhibited efficient photocatalytic activity for the degradation of malachite green (MG) dye without any photosensitizer or cocatalyst under a low-energy light source, the decolorization ratio of MG all reached more than 96.0% within 60 min, and maximal degradation was obtained to be 99.4% (MOF 4). The recycling experiments showed that the degradation rate of MG was still higher than 91% after 10 cycles. In the MOF 4 as representation, the photocatalytic process was explored systematically. The possible mechanism of catalytic degradation was discussed, which proved the existence of efficient oxidation active factors (•O2-, •OH, and h+). The possible intermediates and degradation pathways were investigated based on high-performance liquid chromatography tandem mass spectrometry. Additionally, MOFs 1-4 also exhibited excellent photocatalytic activity for the degradation of methylene blue, methyl violet, rhodamine B, and basic red 9.

WSe2/g-C3N4 for an In Situ Photocatalytic Fenton-like System in Phenol Degradation

An in situ photo-Fenton system can continuously generate H₂O₂ by photocatalysis, activating H₂O₂ in situ to form strong oxidizing ·OH radicals and degrading organic pollutants. A WSe₂/g-C₃N₄ composite catalyst with WSe₂ as a co-catalyst was successfully synthesized in this work and used for in situ photo-Fenton oxidation. The WSe₂/g-C₃N₄ composite with 7% loading of WSe₂ (CNW2) has H₂O₂ production of 35.04 μmol/L, which is fourteen times higher than pure g-C₃N₄. The degradation efficiency of CNW2 for phenol reached 67%. By constructing an in situ Fenton-system, the phenol degradation rate could be further enhanced to 90%. WSe₂ can enhance the catalytic activity of CNW2 by increasing electron mobility and inhibiting the recombination of photogenerated electron-hole pairs. Moreover, the addition of Fe²⁺ activates the generated H₂O₂, thus increasing the amount of strong oxidative ·OH radicals for the degradation of phenol. Overall, CNW2 is a promising novel material with a high H₂O₂ yield and can directly degrade organic pollutants using an in situ photo-Fenton reaction.