Synthesis, Characterization, And Properties Of Scandium Semiconductor Photocatalyst

In this thesis, a new synthesis method using oxalic acid as reactant and flux wasemployed in the system containing scandium and obtained hydrous scandium carbonate,one novel scandium containing compound and two scandium hydrous oxide. Inaddition, theoxalic acid—thiourea synthesis method has been used to synthesize thesystem containing vanadium and two vanadium hydrous oxide,sulfide and oxide wereobtained. In the end,transition metal niobate were synthesized by hydrothermally.In thisthesis, the photocatalytic properties of the obtained materials were investigated bydegradation of methylene blue and water splitting reaction to producing hydrogen underUV irradiation. The main experiment results are as follows:1.(H3O)Sc(CO3)2and a unknown new compand Sc-New were produced byone-step hydrothermal method.They were not retrievaled in the former literatureproviding the evidence that they possessed new construction. At the same time,theywere the precursors of Sc2O3. Sc2O3could be obtained by calcination at certaintemperature and showed preferable activity for splitting water to producinghydrogen.After UV irradiation1h, the efficiency of photocatalytic hydrogen generationfrom water splitting were30,37umol/g/h by calcination (H3O)Sc(CO3)2at500℃andSc-New at600℃respectively. In addition, α-ScOOH and γ-ScOOH were synthesizedby adjusting the hydrothermal condition.By SEM characterization,we knewthatα-ScOOH were small grains andγ-ScOOH were lamellar structure.2. During the preparation of compounds containing vanadium,α-VOOH andγ-VOOH were obtained hydrothermally with oxalic acid as medium. α-VOOH ownedflower-like construction and was completely different from the sphere-like orurchin-like in the reported literature, whileγ-VOOH presented typical lamellar structure.A novel vanadium containing compound was synthesized by altering the condition, itcontained V,S,N,H by EDS analysis and was also flaked by SEM, but we could notknow the exact molecular formula and further characterization was needed. VS2wasflaked with scale-like surface and had certain ability of photoresponse,under UVirradiation1h, the decolorization rate of methylene blue was19.2%.VS4ownedflower-like morphology. Rod-like V2O5was produced by the hydrolysis of NH4VO3andthat NH4V4O10and NH4V3O8were obtained when ammonium hydroxide as solvent. 3. The powder of MnNb2O6(30.32m2/g) and ZnNb2O6(101.78m2/g) with highsurface area were synthesized by hydrothermal method. The results showed that pH hadgreat impact on the purity of products. As compared with the traditional solid statemethod, the sample synthesized by hydrothermal method has more effectivephotocatalytic activities.And the degradation curve showed a trend of line,conformingwith one stage reaction kinetics.In addition, we attempted the hydrothermal method ofniobate containing cerium and lanthanum, CeNbO4.25and the precursor of LaNbO4were obtained.