ABSTRACT
A polymerized ionic liquid (PIL) provides a platform for the development of a high-performance water-free polyelectrolyte-based electrorheological fluid (ERF) because of the presence of large-size hydrophobic ion pairs. However, the large-size hydrophobic ion pairs also easily result in a low glass-transition temperature of an ordinary linear PIL, and consequently, the PIL-based ERF has to be subject to a high leaking current density and a narrow working temperature range. In this paper, we prepared a kind of core-shell-structured polymerized ionic liquid@doubly polymerized ionic liquid (PIL@D-PIL) microsphere with a linear PIL as the core and a physically cross-linked D-PIL as the shell via an evaporation-assisted dispersion polymerization method. The core-shell structure of the sample was observed by scanning electron microscopy and transmission electron microscopy. The thermal properties of the sample were tested by differential scanning calorimetery and thermogravimetric analysis. The ER effect and dielectric polarization of PIL@D-PIL microspheres when dispersed in an insulating nonpolar liquid were studied by a rheometer and dielectric spectroscopy. It shows that the glass-transition temperature and thermal stability of a PIL increased after coating with the D-PIL shell. Under electric fields, the ERF of the PIL@D-PIL microspheres exhibits a significantly reduced leaking current density and an enhanced operating temperature range compared to the ERF of single-PIL microspheres. The PIL@D-PIL microspheres can still maintain good ER effect even if the temperature is higher than the glass-transition point of the PIL core due to the protection of the D-PIL shell.
ABSTRACT
In this work, different BiOBr powders (without and with Zn doping) were prepared. Their specific properties and photocatalytic performance were studied. Zn doped BiOBr showed higher carrier transportation ability, beneficial to high performance photocatalysis. Further analysis and theoretical calculations unveiled that Zn doping resulted in more dispersive energy band structure with improved oxygen vacancy (OV) generation due to lattice distortion. OV acted as trap centers, playing dominant role in carrier transportation enhancement, which also synergized with more dispersive energy band due to Zn doping, improving carrier separation and transfer. Besides, Zn doping would further strengthen trapping effect under OV existence, stimulating synergistic enhancement to spatial charge separation and transfer with OV. With synergy of Zn doping and OV, Zn doped samples produced 1.75 times higher CH4 generation during gas-solid photocatalytic reduction of CO2 under visible light, testifying successful conducting of Zn doping improved photocatalytic capacity on BiOBr.
ABSTRACT
Crystal facet engineering and nonmetal doping are regarded as effective strategies for improving the separation of charge carriers and photocatalytic activity of semiconductor photocatalysts. In this paper, we developed a facial method for fabricating oxygen-deficient Br-doped BiOCl nanosheets with dominating {001} facets through a traditional hydrothermal reaction and explored the impact of the Br doping and specific facets on carrier separation and photocatalytic performance. The morphologies, structures, and optical and photocatalytic properties of the obtained products were characterized systematically. The BiOCl samples prepared by the hydrothermal reaction exhibited square-like shapes with dominating {001} facets. Photodeposition results indicated that photoinduced electrons preferred to transfer to {001} facets because of the strong internal static electric fields in BiOCl nanosheets with dominating {001} facets. Br doping not only contributed to the formation of impurity energy levels that could promote light absorption but introduced a large number of surface oxygen vacancies (VO) in BiOCl photocatalysts, which was beneficial for photocatalytic performance. Moreover, the photocatalytic activities of these products under visible light were tested by degradation of rhodamine B (RhB). Because of the synergistic effect of the dominating {001} facets, Br doping, and rich VO, oxygen-deficient Br-doped BiOCl nanosheets exhibited improved carrier separation, visible light absorption, and photocatalytic efficiency.
ABSTRACT
BiOCl powders with different morphology were obtained through self-assembling. Their photocatalytic performance was tested through degradation of organic dye and mechanism of photocatalytic for obtained samples were investigated. Relevant characterization demonstrated that facet synergy was a main reason of photocatalytic performance promotion due to changed facet exposure and proportion under self-assembling. Theory and experimental analysis manifested that synergistic facet stimulated Z scheme transition in samples with lower (001) facet proportion, which provided favorable condition of 1O2 generation and simultaneously generated prominent charge separation. This work unveiled the facet synergy dominant photocatalytic performance improvement in self-assembling system of BiOCl and verified decisive role of facet proportion in constructing Z-scheme facet junction, which also prompted possibility of improving 1O2 generation through facet engineering under self-assembling.
