| With the increasingly severe environmental degradation of the world, people gradually focus on the environmental pollution problem. Based on photocatalysts,solar energy can be converted into the energy that human can directly utilize, so as to solve the problems such as the depletion of the Earth’s resources and the deterioration of living environments. The graphitic carbon nitride(g-C3N4) as a new environmental protection and pollution-free photoelectric material, the broad space for research and application prospect are worth we tried to pay for it. Herein, the typical synthesis procedure for ternary nanocomposites g-C3N4/MoS2/Ag is via thermal condensation method and g-C3N4/Mo S2/GO using a facile sonochemical method. The morphology,structure, chemical composition and optical properties of the resulting materials were characterized by us. The photoelectrochemical performances of the samples were measured by transient photocurrent test and electrochemical impedance spectroscopy, and photocatalytic activities were evaluated by the degradation of Rhodamine B. The mechanism involving electron–hole separation, transport and photocatalytic were also proposed and discussed. Our results provide insights to the design and large-scale production of semiconductor photocatalysts by interface engineering of the heterojunction and in situ coupling with a co-catalyst. The main content and conclusions are summarized as follows:(1) A proof of concept integrating binary p–n heterojunctions into a semiconductor hybrid photocatalyst is demonstrated by non-covalent doping of g-C3N4 with ultrathin GO and MoS2 nanosheets using a facile sonochemical method.In this unique ternary hybrid, the layered MoS2 and GO nanosheets with a large surface area enhance light absorption to generate more photoelectrons. On account of the coupling between MoS2 and GO with g-C3N4, the ternary hybrid possesses binary p–n heterojunctions at the g-C3N4/MoS2 and g-C3N4/GO interfaces. The space charge layers created by the p–n heterojunctions not only enhance photogeneration, but also promote charge separation and transfer of electron–hole pairs. In addition, the ultrathin MoS2 and GO with high mobility act as electron mediators to facilitate separation of photogenerated electron–hole pairs at eachp–nheterojunction. The highest transient photocurrent density and Rh B degradation rate can be obtained from the g-C3N4/Mo S2/GO, which are about 1.8 and 2.3 times that of the g-C3N4,respectively. As a result, the ternary hybrid photocatalyst exhibits improved photoelectrochemical and photocatalytic activity under visible light irradiation compared to other reference materials.(2) A novel mesoporous ternary photocatalyst consisting of g-C3N4 nanosheets,metallic silver and Mo S2 nanosheets is prepared using AgNO3 as a multifunctional modifier during thermal polymerization of melamine and few-layer MoS2 in a simple one-pot process. The gas bubbles from AgNO3 form an extra soft templates to in situ alter the polymerization behavior of melamine, creating thin g-C3N4 nanosheets and large porous structure that exhibit enhanced light absorption. The solution-based, soft-chemical synthesis enables homogeneous inclusion of metallic silver in the g-C3N4 nanosheets and high dispersibility of ultrathin MoS2 nanosheets in the obtained nanocomposite. In situ coupling between metallic silver and g-C3N4 nanosheets produces nanoscale Mott–Schottky effect, provides an effective channel for charge separation and transfer, and tunes energy band of the latter. More importantly, modulated energy band of g-C3N4 nanosheets synergistically expedites the separation and transfer of photogenerated electron–hole pairs at the interface of two-dimensional g-C3N4/Mo S2 heterojunction. The highest transient photocurrent density and Rh B degradation rate can be obtained from the g-C3N4/MoS2/Ag, which are about 3 and 3.8 times that of the g-C3N4, respectively. As a result, the ternary nanocomposite exhibits improved photoelectrochemical performance and photocatalytic activity. |
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