Search

Hydrogen peroxide (H2O2) photoproduction in seawater with metal-free photocatalysts derived from biomass materials is a green, sustainable, and ultra environmentally friendly way. However, most photocatalysts are always corroded or poisoned in seawater, resulting in a significantly reduced catalytic performance. Here, we report the metal-free photocatalysts (RUT-1 to RUT-5) with in-situ generated carbon dots (CDs) from biomass materials (Rutin) by a simple microwave-assisted pyrolysis method. Under visible light (λ ≥ 420 nm, 81.6 mW/cm2), the optimized catalyst of RUT-4 is stable and can achieve a high H2O2 yield of 330.36 µmol/L in seawater, 1.78 times higher than that in normal water. New transient potential scanning (TPS) tests are developed and operated to in-situ study the H2O2 photoproduction of RUT-4 under operation condition. RUT-4 has strong oxygen (O2) absorption capacity, and the O2 reduction rate in seawater is higher than that in water. Metal cations in seawater further promote the photo-charge separation and facilitate the photo-reduction reaction. For RUT-4, the conduction band level under operating conditions only satisfies the requirement of O2 reduction but not for hydrogen (H2) evolution. This work provides new insights for the in-situ study of photocatalyst under operation condition, and gives a green and sustainable path for the H2O2 photoproduction with metal-free catalysts in seawater. [ABSTRACT FROM AUTHOR]

Cerium‐based Metal‐Organic frameworks (Ce‐MOFs) are attracting increasing interest due to their similar structural features to zirconium MOFs. The redox behavior of Ce(III/IV) adds a range of properties to the compounds. Recently, perfluorinated linkers have been used in the synthesis of MOFs to introduce new characteristic into the structure. We report the synthesis and structural characterization of Ce(IV)‐based MOFs constructed using two perfluorinated alkyl linkers. Their structure, based on hexanuclear Ce6O4(OH)412+ clusters linked to each other by the dicarboxylate ions, has been solved ab‐initio from X‐ray powder diffraction data and refined by the Rietveld method. The crystallization kinetics and the MOF formation mechanism was also invesitigated by Synchrotron radiation with XAS spectroscopies (EXAFS and XANES). The MOFs present the same fcu cubic topology as observed in MOF‐801 and UiO‐66, and they showed good stability in water at different pH conditions. The electronic structure of these MOFs has been studied by DFT calculations in order to obtain insights into the density of states structure of the reported compounds, resulting in band gaps in the range of 2.8–3.1 eV. Their catalytic properties were tested both thermally and under visible light irradiation for the degradation of methyl orange (MO) dye. [ABSTRACT FROM AUTHOR]

Large-scale green tides in the Yellow Sea occurred for 13 consecutive years since 2007. The unusual co-occurrence of green tides and golden tides occurred in the Yellow Sea in 2017. The causative species are Ulva prolifera and/or Sargassum horneri. Previous studies on physiological response characteristics of U. prolifera and S. horneri are done in the laboratory mainly, and there is no in-situ comparative study in this regard. In this study, the in-situ physiological response characteristics of both species were measured. The results indicated that cyclic electron flow and antioxidant system play more important roles in protecting U. prolifera, while non-photochemical quenching is more important for adapting to the environment in S. horneri. U. prolifera has a stronger ability to utilize nutrients to rapidly increase its biomass under a suitable condition compared to S. horneri. [ABSTRACT FROM AUTHOR]

Understanding the structure‐activity relationship of catalytic reactions at a molecular level still remains a great challenge. Herein, shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) is employed to in‐situ study the catalytic hydrogenation of para‐nitrothiophenol (pNTP) on Pt‐based nanocatalysts with different size and composition. The nanocatalysts are assembled on pinhole‐free shell‐isolate nanoparticles (SHINs), which work as Raman amplifiers to enhance the Raman signals of species on the catalysts, allowing the in‐situ monitoring of catalytic reactions carried out on the catalysts. Using this strategy, we find that the catalytic activity of the Pt nanocatalysts shows a volcanic trend with the Pt size, and that PtM (M=Ni or Cu) bimetallic nanocatalysts display much higher performance compared with Pt due to better activation of the nitro group. This work demonstrates that SHINERS is a promising technique for in‐situ study of nanocatalysis thus can deepen the understanding of the behaviors of different catalysts. [ABSTRACT FROM AUTHOR]

Airflow disorder in inlet shafts and related crossheadings, caused by local natural ventilation pressure, is a complicated thermodynamic phenomenon. The conception of local natural ventilation pressure is proposed based on a simplified ventilation system. Airflow disorder principle is analyzed theoretically and verified by similar simulation experiment and in-situ study. Research results show that local natural ventilation pressure will form when average temperature difference or density difference of air-column exists among inlet shafts in an underground mine with exhaust ventilation. When changing in a large range, local natural ventilation pressure will cause airflow disorder in inlet shafts or related crossheadings. The research results have guiding significance for promoting the stability of ventilation system and improving the working environment of underground mines. [ABSTRACT FROM AUTHOR]