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In recent years, many efforts have been devoted to boost molecular oxygen activation in semiconductor. This is because the reactive oxygen species (ROS) induced by molecular oxygen activation have been confirmed to play a great role in environmental remediation. Herein, we proposed a self-assembled plasmonic p-n heterojunction of WO3/Ag@Ag2O with enhanced molecular oxygen activation ability under visible and near-infrared (NIR) light irradiation. The prepared p-n heterojunction is favorable for the migration and separation of photo-generated hot charge carriers, which can promote the transformation of molecular oxygen to ROS with enhanced photocatalytic performance for norfloxacin (NOR) decomposition. The trapping experiments and Electron spin response (ESR) spectra demonstrate that both superoxide ( O2−) and singlet oxygen (1O2) are the main functional ROS for NOR degradation. The yield amount of O2− in the prepared hybrid catalyst is higher than that of pristine catalyst from nitrotetrazolium blue chloride (NBT) degradation. The sustainable generation of 1O2 is mainly ascribed to the charge transfer and energy transfer. Fluorescence spectra method is employed to confirm the generation of hydrogen peroxide (H2O2). The intermediates of NOR degradation are identified by LC/MS, and the possible degradation pathway is proposed in detail. A reasonable charge transfer pathway for the ultra-high hot charge carrier separation is studied. In addition, the as-prepared hybrid composite shows excellent photocatalytic performance for the degradation of rhodamine B (RhB) and ciprofloxacin (CIP). This study provides a promising avenue for fabrication of semiconductor with boosting molecular oxygen activation.

2,2′,4,4′-Tetrabrominateddiphenyl ether (BDE-47), as one of polybrominated diphenyl ethers (PBDEs), has been proven to be global contaminant owing to widespread utilization as flame retardant. Herein, a novel visible-light-driven (VLD) artificial indirect Z-scheme system of Ag@Ag3PO4/g-C3N4/rGO is finely designed for BDE-47 removal assisted with abundant solar energy. The novel hybrid composite exhibits an enhanced reductive debromination activity with removal efficiency of 93.4% under visible light irradiation (λ > 420 nm) for 120 min, which is 173.65 times higher than pristine g-C3N4 catalyst. A series of experiments in terms of the environmental effects of initial concentration, pH, solvent and light source are performed to optimize the photocatalytic performance. The presence of rGO as an excellent storing and shuttling medium, can further facilitate the charge carrier separation in the indirect Z-scheme system for the enhanced photo-reduction debromination performance. The accumulated electrons on the solid catalyst can attack the ortho-Br of BDE-47 to formation of BDE-28, and then so on. The protons (H+) can be reduced to atomic hydrogen (H°), which can greatly weaken para-Br of BDE-47 to generation of BDE-17. Furthermore, the remaining holes can react with CH3OH to generate CH2OH radical, and then further directly produce electron for debromination process. A possible debromination pathway for BDE-47 was proposed. This work provides a green and promising strategy utilizing solar energy to remove BDE-47 in the liquid medium by virtue of VLD composite.

To achieve complete removal of persistent organic pollutant from water system, an efficient, stable, magnetic and low-energy sulfate radical-based advanced oxidation process (SR-AOPs) is in desirable to be established. In this work, magnetic trimetallic oxides Co3MnFeO6 nanoparticles were successfully synthesized and utilized as novel heterogeneous catalysts to activate peroxymonosulfate (PMS) for the degradation of carbamazepine (CBZ), a recalcitrant organic pollutant. In the degradation tests, Co3MnFeO6/PMS system showed excellent performance that 99.2% of CBZ could be removed at a relative shorter time (30 min) and in a wider pH range from 3 to 10. More in-depth investigation found that synergistic effects between Co, Mn and Fe in Co3MnFeO6 catalyst were responsible for the efficient generation of sulfate radical from PMS activation. And the roles of Co, Mn and Fe in synergistic effect were identified as: the redox cycles of Co and Mn mainly worked for the activation of PMS, and Fe mainly provided magnetism for Co3MnFeO6 catalyst as well as the adsorption site for PMS and CBZ. Moreover, it was found that Co3MnFeO6 catalyst maintained high activity and robust magnetism during repeated batch experiments. Even in real wastewater samples (municipal wastewater, tap and river water), Co3MnFeO6/PMS system was capable of high activity for CBZ removal, indicating that Co3MnFeO6/PMS system possessed promising potential in practical applications. The possible CBZ degradation pathways were also proposed based on the detected intermediates. This Co3MnFeO6/PMS system may provide some new inspirations for the construction of multiple metal-based catalysts in AOPs.

Among several factors that influence the effectiveness of a semiconductor mediated photocatalysis, efficient charge separation and broadened light absorption are regarded as two of the most important parameters. Herein, a series of plasmonic p-n heterojunction Ag/Ag2O/PbBiO2Br photocatalysts with wide spectrum responses were successfully fabricated through a facile precipitation-calcination method. The obtained samples display exceptional photocatalytic performance for the degradation of tetracycline (TC), and the results reveal that the 10 wt% Ag/Ag2O/PbBiO2Br exhibits the optimal activity, which can efficiently decompose 84.4% of TC after 90 min of visible light irradiation. While under NIR light irradiation, the TC removal ratio can still reach 50.9% with 240 min. Besides, no significant deterioration in the degradation performance is observed even after four cycling runs. The photoactivity enhancement of Ag/Ag2O/PbBiO2Br can be credited to the synergistic effect between the local surface plasmon resonance (LSPR) effect of metallic Ag and the p-n heterojunction of Ag2O/PbBiO2Br, which not only greatly broadens the light utilization, but also remarkably accelerates the charge separation. The radical trapping experiments and the ESR measurements ascertains that O2−, h+ and OH play a critical role in the degradation of TC under visible light irradiation, while O2− and h+ become the major reactive species in NIR light-driven reaction. According to the experimental results, the plausible reaction mechanisms for TC degradation over Ag/Ag2O/PbBiO2Br composite are proposed under both visible and NIR light irradiation. This work provides some guidance for rational construction of novel plasmonic p-n heterojunction photocatalysts to meet ever-increasing environmental requirements.

The heterointerface between different components of composite photocatalyst, which acts as the channel of charge transfer, is of crucial importance to photocatalytic performance. In this study, a series of tightly connected CdS/SnO2 heterojunction photocatalysts were prepared via simple hydrothermal process containing CdSnO3·3H2O as templates and thiourea as sulfur source. The crystal phase, morphology, interface structure, and composition of the obtained samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy. It was found that the size and morphology of CdS/SnO2 composites can be conveniently controlled by using different CdSnO3·3H2O templates. The results of UV-vis diffuse reflectance spectrum (DRS), electrochemical impedance spectroscopy (EIS) and photoluminescence spectra (PL) demonstrated that the formation of ultrasmall CdS/SnO2 heterostructure remarkable enhance visible light absorption and effectively promote the separation of photogenerated charge carriers. Moreover, the formed intimate heterointerface can maximize the superior electron conductivity of SnO2 and thus, greatly speed up the transfer of photo-generated electron. Compared to the single CdS, the CdS/SnO2 composites exhibited excellent photocatalytic performance towards Cr(VI) reduction and tetracycline (TC) degradation under visible light irradiation, which was ascribed to the enhanced visible light absorption and rapid separation of electrons and holes. The trapping experiments and ESR proved that ·O2– and h+ are the primary reactive species involved in the photocatalytic degradation of TC. 3D EEMs results indicated that the CdS/SnO2 heterojuction photocatalysts owned strong mineralization ability on the TC molecules degradation. The energy band alignments of CdS/SnO2 heterostructure were determined by combining DRS and XPS results. Ultimately, a possible photocatalytic mechanism was proposed.

Developing green and highly efficient water disinfection technique is of great importance to public health. Herein, a near-infrared (NIR) light-triggerable thermo-sensitive defective molybdenum oxide-nitrogen doped carbon (MoO3-x/NCNs) composite was fabricated and applied to water disinfection. With the synergy of photodynamic and photothermal effects, the MoO3-x/NCNs achieve a rapid and effective inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as compared to photocatalytic treatment or thermal catalytic alone. Particularly, MONC-3 with optimal ratio can completely inactivate 7.6 log of E. coli and S. aureus within 60 min and 100 min, respectively. The MONC-3 hybrid exhibits efficient charge separation and migration ability due to the formation of Schottky heterojunction, resulting in the highly enhanced O2− (11.34 × 10−10 M) generation activity. Meanwhile, excellent NIR light absorption and photothermal conversion efficiency (52.6%) of MONC-3 can generate local high temperature to promote photocatalytic reaction rate and destruct the bacterial integrity. The monitoring of cell damage process confirmed the irreversible death of bacteria. Based on density functional theory (DFT) calculation, the antibacterial mechanism and Schottky effect were clarified. This work provides new insights for constructing a water disinfection strategy based on plasma-induced photothermal synergy catalysis.