| With the rapid economic growth,environmental and energy issues have become increasingly prominent.Most of traditional methods to prepare high value-added chemicals have exacerbated energy and environmental problems because of their high energy consumption inputs.With the development of semiconductor photocatalytic technology,humans have entered a new area in which energy and environmental problems can be solved simultaneously.The use of solar energy to produce high-value chemicals can greatly reduce energy consumption,therefore achieving sustainable development in the future.Peroxydisulfate(S2O82-)and hydrogen peroxide(H2O2)are two kinds of important chemicals,however,there are few studies on the photocatalytic generation of S2O82-and H2O2,which restricts the development of photocatalytic technology in this field.Tungsten oxide(WO3)is a common n-type semiconductor material in photocatalysis.It has the advantages of non-toxicity and harmless,stable under acidic conditions and good response to visible light,making WO3 an important material for photocatalytic production of S2O82-and H2O2.However,the photocatalytic performance of WO3 is still very poor due to easy recombination of photogenerated electron-hole pairs.Therefore,in this thesis,modified WO3 was fabricated to achieve efficiently photocatalytic production of S2O82-and H2O2,and the following studies were carried out;(1)The activity of photocatalytic production of S2O82-and H2O2 was enhanced using platinum(Pt)loaded WO3 via different methods.The results of activity tests showed that the sample loaded using photodeposition(PD)method ahcieved the best activity for S2O82production,which was 2.1 and 4.4 times that of the chemical reduction(CR)method and the impregnation(IM)method,respectively.The sample prepared by IM method achieved the simultaneous production of S2O82-and H2O2 with the ratio reached 1:1.X-ray photoelectron spectroscopy(XPS)analysis showed that the difference in activity might be due to the different chemical states of Pt on WO3 surface.(2)The effect of Pt chemical sate on the activity was further studied.The ratio of metallic Pt(Pt0)to PtOx could be controlled by changing the MeOH concentration during photodeposition.It was found that the Pr0/PtOx ratio gradually decreased with the increasing of MeOH concentration,furthermore,only the chemical states were different among different samples.Based on the results of photoelectric chemical experiments and activity tests,PtOx was proposed to be as an oxidation cocatalyst for accelerating the H2O2 formation,on the other hand,Pt0 is as a reduction cocatalyst to promote the O2 reduction to H2O.The dual cocatalyst accelerated the separation efficiency of electron-hole pairs under irradiation and greatly promoted the photocatalytic activity(3)Inspired by the dual cocatalyst system and to reduce the use of noble metal Pt,dual metals of Pt and Au loaded WO3 were fabricated.Morphological measurement and energy spectrum scanning results showed that Pt and Au form core-shell structure.The presence of the core-shell structure can further enhance the S2O82-activity.After visible light(λ>420 nm)irradiation under 300 W Xe lamp for 3 h,the photocatalytic activity of Pt-Au alloy catalyst to produce S2O82-reached 36 μmol,which was 1.7 times that of a single Pt loading and 35 times that of a single Au loading.In this thesis,the properties of WO3 loaded by Pt and Pt-Au alloy on the photocatalytic production of S2O82-and H2O2 were studied,which provided referential information for the reaction mechanism.This thesis could provide promising methods to produce H2O2 and S2O82-simultaneously using H2O,O2 and H2SO4 with photocatalysts. |
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