Preparation?Characterization And Applications In Nitrogen Fixation And Organic Photosynthesis Of Metal Sulfides

In this thesis,metal sulfide photocatalytic materials with good structureswere prepared and theiractivity testswereevaluated by photocatalytic nitrogen fixation and photocatalytic oxidation of benzyl alcohol to benzaldehyde and generate hydrogen under visible light.Finally,based on a series of characterizations,a possible photocatalytic reaction mechanismwas proposed.The first part,Cd0.5Zn0.5S photocatalyst was synthesizedby a simple hydrothermal methodusing water as a solvent and cadmium nitrate tetrahydrate,zinc nitrate hexahydrate,L-cysteine as precursors.The composition and microstructure,texture and optical properties of the as-synthesized samples were characterized by X-ray diffractometer(XRD),X-ray photoelectron spectroscopy(XPS),scanning and transmission electron microscopy(SEM and TEM),specific surface area(BET),UV-vis diffuse reflectometer(UV-Vis DRS).The photocatalytic performance of the as-synthesized sampleswas evaluated by photocatalytic reduction of N2 to NH4+.The experimental results indicate that when the hydrothermal temperature is 200?,the photocatalytic activity of the as-synthesized Cd0.5Zn0.5S sample is the besttoward the photocatalytic reduction of N2 to NH4+.That's,the ammonia production could reach 2.93 mmol/L under visible light(??420 nm)irradiation for 2 hours.The possible reaction mechanism of photocatalytic nitrogen fixation was speculated using an electrochemical workstation and an electron paramagnetic resonance spectrometer(EPR).The second part,Zn3In2S6and Ni/Zn3In2S6photocatalystswere synthesized by simple hydrothermal and in-situ photodeposition methods.The experimental results show that the photocatalytic activities of the synthesized Ni/Zn3In2S6 composites have been greatly improved in the system of photocatalytic oxidation of benzyl alcohol to benzaldehyde and generating H2.Among them,the photocatalytic performance of 0.5%Ni/Zn3In2S6 composite is the best.The yields of benzaldehyde and hydrogen are 1595.69 and 1236.62 ?mol,which is approximately 4.85 and 4.08 times higher that that of monomer Zn3In2S6sample.Meanwhile,it is proved by the control experiments of the trapping agents(triethanolamine and CC14)that photogenerated electrons and holes play very important rolesduring the photocatalytic reaction process.Finally,a possible reaction mechanism of photocatalytic oxidation of benzyl alcohol to benzaldehyde and hydrogen evolutionwas proposedthrough a series of characterizations of samples(such as XRD,BET,TEM and PL).