A Novel and Reusable RGO/ZnO with Nanosheets/Microparticle Composite Photocatalysts for Efficient Pollutants Degradation

Abstract

In this paper, we designed and synthesized a novel structure ZnO with the nanosheets grown on the surface of dumbbellshape ZnO via a simple hydrothermal route, and exhibits excellent photoelectrochemical performance. The reason is that nanosheets enhance charge generation, separation and transfer. Graphene as a co-catalyst and anti-photocorrosion material were coated on the surface of ZnO and further enhanced the photoelectrochemical properties. In process of photodegradation RhB, the experiments reveal that ZnO with 1.5 wt% RGO displayed highest rate constant of 0.0562 min À 1 , which is about 4 times better than pristine ZnO (heating 9 h) and several times higher than other RGO/ZnO composites. Meanwhile, the recycle experiments of 1.5 wt% RGO/ZnO suggest that it has excellent stability, reusability and excellent photocatalytic activity. The work provides a new strategy that developing nanosheets with high-energy plane grown on the surface of semiconductor particles to enhance photoelectrochemical performance and reusability. Results and discussionThe SEM images and TEM images were used to investigate the morphologies and structures of the ZnO-9, ZnO-10 and the . (a) Degradation efficiency of RhB catalyzed by ZnO and RZ-10 with different RGO contents; (b) pseudo-first-order kinetic plots; (c) the rate constant of samples; (d) Recycling photodegradation of RhB over 1.5 wt% RZ-10 under Xe lamp irradiation. 2 3 4 5 6 7 8

Dual II Heterojunctions Metallic Phase MoS2/ZnS/ZnO Ternary Composite with Superior Photocatalytic Performance for Removing Contaminants

“…The as‐prepared materials were characterized by X‐ray diffraction (XRD), and corresponding crystalline structures of the resultants were displayed in Figure . In the XRD pattern of ZnO (Figure a), the major diffraction peaks are located at 31.84, 34.48, 36.29, 47.60, 56.72, 62.83, 66.46, 67.90, and 69.23°, which can be indexed as the hexagonal wurtzite structure (JCPDS No.36–1451) . The XRD patterns of MZ composites with different molar ratios of Mo and Zn are shown in Figure b.…”

“…The detected elements were present in the corresponding as‐prepared materials, without any impurities. As shown in Figure b, for pure urchin‐like ZnO, two major peaks of Zn 2p, located at 1021.49 and 1044.54 eV, correspond to Zn 2p 3/2 and Zn 2p 1/2 , respectively . When MoS 2 was grown in situ on the ZnO surface, the two Zn 2p peaks were increased.…”

“…In the XRD pattern of ZnO (Figure 3a), the major diffraction peaks are located at 31.84, 34.48, 36.29, 47.60, 56.72, 62.83, 66.46, 67.90, and 69.238, which can be indexed as the hexagonal wurtzite structure (JCPDS No.36-1451). [8] The XRD patterns of MZ composites with different molarr atios of Mo and Zn are shown in Figure 3b.W hen molar ratio of Mo and Zn was 1:2, there were no significant diffractionp eaks of ZnO and the diffraction peaks can be exactly assigned to ZnS (JCPDS No.39-1363). The phenomenon may be due to the excessive (NH 2 ) 2 CS-generated H 2 S under hydrothermal conditions, and subsequentr eaction with ZnO to obtain ZnS;t he strong diffraction peaks of ZnS obscuring the diffraction peak of ZnO.…”

“…Particularly, the merits of large surface area, unidirectional charge migration, and effectively light scattering make urchin‐like ZnO more attractive than one‐dimensional and two‐dimensional nanostructures in photodegrading pollutants . Nevertheless, there are some weaknesses of ZnO that hinder its practical application, such as photocorrosion, large band gap energy, and fast recombination of electron‐hole pairs . Constructing a ZnO/semiconductor heterojunction composite is a promising method to overcome the above‐mentioned defects .…”

“…[7] Nevertheless, there are somew eaknesseso fZ nO that hinder its practical application, such as photocorrosion,l arge band gap energy, and fast recombinationo fe lectron-hole pairs. [8] Constructing aZ nO/ semiconductor heterojunction composite is ap romising method to overcomet he above-mentioned defects. [9] For instance, aZ -Scheme heterojunction was constructed by self-assembly using graphene film and ZnO quantumd ots, which obviously increases the charge separation efficiency.…”