| Semiconductor photocatalyst is used to drive a series of photoredox reaction with theutilize of sunlight, it can convert solar energy into chemical energy or direct degradationand mineralization of organic pollutants. Therefore, it is regarded as a significantapplication prospect in solving the problem of energy shortage and environmentalpollution. In recent years, polymeric graphitic carbon nitride (g-C3N4) as a metal-freevisible-light-driven photocatalyst, has been attracted much attention for the light catalyticconversion of solar energy owning to its appealing electronic structure, excellent chemicalstability, thermal stability and capable of harvesting light with suitable band gap energy of2.7eV. Its development and utilization have been a research hotspot. Generally, g-C3N4was used in water splitting for hydrogen and oxygen evolution, degradation of pollutionsand so on.However, the traditional g-C3N4has many disadvantages, such as small specificsurface area, fast recombination and low catalytic activity, many efforts are therefore stillneeded to overcome the limitation in order to improve the photocatalytic performance.Herein, via the use of urea and dicyandiamide as precursor, the porous graphitic carbonnitride material has been prepared by pyrolysis of dicyandiamide in air using urea asbubble template. Afterwards, different content of MoS2were introduced on porousg-C3N4to construct heterostructures with a facile solvothermal method using ethyleneglycol as solvent. Thus a series of MoS2-g-C3N4composite materials were prepared. Themorphology, crystalline phases, structure and optical properties of the samples werecharacterized by Transmission electron microscopy(TEM) and mapping analysis, X-raydiffraction(XRD), Fouriertransform infrared spectroscopy(FT-IR),Brunauer-Emmett-Teller method(N2-BET), EA element analysis, Inductively coupledplasma-atomic emission spectroscopy(ICP-AES) measurement, X-ray photoelectronspectroscopy(XPS), Ultraviolet-visible diffuse reflection spectroscopy(UV-Vis) andPhoto-luminescence spectra(PL). Moreover, we have evaluated its photocatalyticperformance with the help of hydrogen generation from water splitting under visible lightirradiation and surveyed the co-catalyst MoS2, calcinations temperature on the propertiesof samples, further investigate the influence factors and mechanism of the photocatalytic performance.The main research results of this paper as follows:(1) With urea and dicyandiamide as raw materials, this paper prepared the porousg-C3N4. The MoS2-g-C3N4resultant composite was synthesized by a facile solvothermalmethod using ethylene glycol as solvent. The result of photocatalysis shows that theresultant composite exhibits enhanced photocatalytic hydrogen-evolution activity undervisible-light irradiation with a rate of43.64umolh-1. It also figures that the ratio ofcocatalyst MoS2, calcination temperature exist the best value. The catalysis experimentshows when g-C3N4synthetise in the condition of600℃at5℃/min heating rate, thenloaded with4wt%MoS2, the obtained composite exhibited the highest activity undervisible light irradiation. Moreover, via the circulation experiment, the MoS2-g-C3N4composite reveal a goodstability for hydrogen evolution under the visiblelight irradiation.(2) The characterization results shows that the intimate heterostructure betweeng-C3N4and MoS2was formed, the crystallinity, surface area, pore volume and band gapwas enlarged after solvent thermal process.(3) A possible mechanism for the hydrogen evolution over MoS2-g-C3N4is proposed.The activity enhancement of MoS2-g-C3N4composite can be ascribed to the synergisticcontributions of intimate heterostructure. Also, MoS2as an electronic collector can absorbphotoelectron, thus improve the separation of photogenerated electron-hole pairs andefficiently suppresse charge recombination rate of photo-generated. This study may createa new and easy method for designing and synthesis of heterogeneous photocatalyst withhighly catalytic acticity and provide certain reference for practical environment function. |
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