Appropriate oxygen vacancies and Mo-N bond synergistically modulate charge transfer dynamics of MoO3-x/S-CN for superior photocatalytic disinfection: Unveiling synergistic effects and disinfection mechanism.

Highly efficient charge transfer is a critical factor to modulate the photocatalytic activity. However, the conscious modulation of charge transfer efficiency is still a great challenge. Herein, a novel interfacial Mo-N bond and appropriate oxygen vacancies (OVs) modulated S-scheme MoO3-x/S-CN heterojunction was rationally fabricated for efficient photocatalytic disinfection. The results of characterizations and density functional theory (DFT) calculations suggested that the enhanced charge transfer dynamics is ascribed to the optimizing oxygen vacancies density and forming interfacial Mo-N bond. It can improve charge transfer efficiency from 36.4% (MoO3-x) to 52.5% (MoO3-x/S-CN) and produce more reactive oxygen species (ROS), achieving entirely inactivate of 7.60-log E. coli and S. aureus within 50 min and 75 min. Besides, MoO3-x/S-CN can well resist the disturbance from the coexisting substances, and can be applied in a wide pH range, and even authentic water bodies. Monitoring of bacterial antioxidant systems and membrane integrity revealed that bacterial inactivation begins with the oxidation of cell membrane and dies from leakage of intracellular substances and destruction of cell structure. This work provides an inspiration on consciously modulating S-scheme charge transfer efficiency by optimizing oxygen vacancies density and atomic-level interface control for promoting the photocatalytic antibacterial activity.

Insights into the role of reactive oxygen species in photocatalytic H2O2 generation and OTC removal over a novel BN/Zn3In2S6 heterojunction.

Developing photocatalysts with superior performance to generate hydrogen peroxide (H2O2) and degrade oxytetracycline (OTC) is an effective strategy for the treatment of energy crisis and water purification. Herein, BN nanosheets were anchored onto the Zn3In2S6 microspheres for the research. Experimental and density functional theory (DFT) results demonstrate that due to different work functions and unique 2D/2D contact, the electron is spatially separated in BN/Zn3In2S6 nanocomposite, which increases the electron transfer efficiency from 43.7% (Zn3In2S6) to 55.6% (BN/ZIS-4). As a result, BN/ZIS-4 with optimal ratio of BN and Zn3In2S6 exhibits the highest OTC degradation efficiency (84.5%) and H2O2 generation rate (115.5 µmol L-1) under visible light illumination, which is 2.2 and 2.9 times than that of pristine Zn3In2S6. H2O2 generation is dominated by two pathways: two-step single-electron process (O2 → ∙O2- → H2O2) and another way (O2 → ∙O2- → 1O2 → H2O2). In the process of degrading OTC, ∙O2-, 1O2 and ∙OH are regarded as the main active species. This work offers a new insight for designing efficient, stable and reusable photocatalysts to solve current environmental conundrums.

2D/2D Heterojunction systems for the removal of organic pollutants: A review.

Photocatalysis is considered to be an effective way to remove organic pollutants, but the key to photocatalysis is finding a high-efficiency and stable photocatalyst. 2D materials-based heterojunction has aroused widespread concerns in photocatalysis because of its merits in more active sites, adjustable band gaps and shorter charge transfer distance. Among various 2D heterojunction systems, 2D/2D heterojunction with a face-to-face contact interface is regarded as a highly promising photocatalyst. Due to the strong coupling interface in 2D/2D heterojunction, the separation and migration of photoexcited electron-hole pairs are facilitated, which enhances the photocatalytic performance. Thus, the design of 2D/2D heterojunction can become a potential model for expanding the application of photocatalysis in the removal of organic pollutants. Herein, in this review, we first summarize the fundamental principles, classification, and strategies for elevating photocatalytic performance. Then, the synthesis and application of the 2D/2D heterojunction system for the removal of organic pollutants are discussed. Finally, the challenges and perspectives in 2D/2D heterojunction photocatalysts and their application for removing organic pollutants are presented.

Response of nitritation performance and microbial community structure in sequencing biofilm batch reactors filled with different zeolite and alkalinity ratio.

Ammonium (NH4+-N) adsorption capacity of zeolite varies from place to place, a unique attempt to use different zeolite as adsorbent media in sequencing biofilm batch reactor (SBBR) for maintaining appropriate free ammonia (FA) range to achieve partial nitritation. SBR filled with synthetic zeolite (SSBBR) and natural zeolite (NSBBR) were applied to evaluate the NH4+-N adsorption capacity impacts on nitrogen transformation and microbial characteristics. Significant differences in nitrite production rate (NPR) were both observed in two reactors during 4 different alkalinity ratios. The highest NPR in SSBBR and NSBBR were both obtained when the alkalinity ratio was 5:1 with the values of 1.11 and 0.90 kg N/(m3·d), respectively. According to Haldane model with inhibition by FA, the kinetics of the reaction were analyzed. High-throughput sequencing analysis results further presented that SSBBR had higher relative abundance average of nitrosobacteria in genus level, which was in favor of better partial nitritation.