Preparation,Characterization And Applications In Photoelectrochemistry Of WO_x And MoO_x Materials

In the modern society,human beings are facing the both challenges of environmental pollution and energy shortage.Therefore,the photocatalytic technology based on semiconductor and the dye-sensitized solar cell?DSSC?are the effective routes to solve the environmental and energy crises.However,the traditional TiO2 photocatalyst due to wide band gap and low photocatalytic activity and the DSSC due to employ noble metal Pt as counter electrode make the developments of photocatalytic technology and DSSC hindered.Nonstoichiometric W₁₈O₄₉ has a monoclinic structure with a narrow band gap,good response to sunlight,and excellent electrical conductivity.It can be applied in semiconductor photocatalysis and other fields.That the nonstoichiometric molybdenum oxides have multivalence states and the transformation between the several valence states in the application process make it have good chemical activity and electron transport property.In particular,Mo₄O₁₁ has a lower resistivity of 10-4 ?·cm and a better transporting property,which make it become an ideal photocatalyst and photocathode material.In this thesis,the surface property of three-dimensional ordered macroporous?3DOM?WO,materials was first analyzed,and MoO_x materials with high Mo₄O₁₁ content were,for the first time,prepared.The following works were finished in detail:?1?Monodisperse PMMA microspheres with different particle sizes were synthesized by non-emulsion polymerization process and assembled into colloidal crystal templates by centrifugation or constant-temperature water bath method.The hydrofluoric acid solution of WO3 was used to soak the PMMA colloidal crystal template.After drying and calcining the colloidal crystal template filled with WO3,WO_x three-dimensional ordered macroporous?3DOM?structure was obtained.The samples were characterized by SEM,XRD,XPS,Raman and UV-Vis spectra.?2?The W₁₈O₄₉ nanomaterials with different morphologies?nanowires,spindle,sea urchin?were synthesized using solvothermal process.The samples were characterized by SEM and XRD.The prepared W₁₈O₄₉ nanomaterials were used as photocatalyst to degrade methyl orange?MO?under UV and visible light irradiation.The results show that the W₁₈O₄₉ nanowires and spindle have excellent degradation efficiencies of 94%and almost 100%,respectively,for MO.?3?The MoO_x materials were prepared using different process and the effect of process conditions on the phase composition and content was studied.?The ammonium molybdate was directly reduced in 5 vol%H₂/Ar atmosphere,and the MoO_x with as high as 84.8%Mo₄O₁₁ content was obtained at 600? for 2h.?First MoO3 was synthesized through hydrothermal method,then MoO3 was reduced in 5vol%H₂/Ar atmosphere,obtaining as high as 92%Mo₄O₁₁ content at 600 C for 2h.?MoO3 was first obtained by calcining ammonium molybdate in the air at 650 C,then MoO3 was reduced at 5 vol%H₂/Ar atmosphere,obtaining the highest Mo₄O₁₁ content of 98.5%at 600? for 2h.MoO_x samples were characterized using SEM,XRD,XPS,Raman and UV-vis spectra.The results show that the MoO_x with 98.5%Mo₄O₁₁ content has the degradation efficiency of as high as 97%.DSSC with Mo₄O₁₁ as counter electrode was preliminarily explored.