MnWO_(4)/WO_(3) p-n heterojunction films were fabricated using a one-step method consisting of the plasma electrolytic oxidation(PEO)of titanium in homogeneous electrolytes containing paratungstate ions and stable wat...MnWO_(4)/WO_(3) p-n heterojunction films were fabricated using a one-step method consisting of the plasma electrolytic oxidation(PEO)of titanium in homogeneous electrolytes containing paratungstate ions and stable watersoluble EDTA-chelated manganese.The influences of the formation current density and W:Mn molar ratio of the electrolyte,which was varied from 1:2 to 2:1,on the composition,morphology,and optical and photocatalytic properties of the resulting coatings were studied.X-ray diffraction analysis,scanning electron microscopy,energy dispersive X-ray analysis,Raman spectroscopy,and ultraviolet diffuse reflectance spectroscopy were used to characterize the formed composites.Regardless of the W:Mn ratio of the electrolyte,the coatings contained crystalline t-WO_(3) and m-MnWO_(4).Depending on the formation conditions,the optical band gap energies of the composites varied from 2.63 to 3.01 eV.The largest absorption red shift and lowest band gap energy were observed in the film composite formed in an electrolyte with W:Mn=2:1,at a current density of 0.2 A cm^(−2).Composites obtained in electrolytes with W:Mn ratios of 2:1 and 1:1 exhibited photocatalytic activity in the degradation of rhodamine C and methyl orange dyes in the presence of 10 mmol L^(–1) H_(2)O_(2) under ultraviolet and visible light irradiation.The role of hydrogen peroxide in this dye degradation on PEO-coated composites under light irradiation is discussed.展开更多
The Bi_(2)O_(3)/Bi_(2)SiO_(5) heterostructures were obtained with various samples of silica as a precursor:on the basis of biogenic silica isolated from rice husk and rice straw and the silica of mineral ori-gin.A mix...The Bi_(2)O_(3)/Bi_(2)SiO_(5) heterostructures were obtained with various samples of silica as a precursor:on the basis of biogenic silica isolated from rice husk and rice straw and the silica of mineral ori-gin.A mixture of Bi(NO_(3))_(3) and SiO_(2) with a mass content of 15%was used for synthesizing all the samples.Fourier transform infrared(FT-IR)spectroscopy,scanning electron microscope(SEM),X-ray phase,X-ray fluorescence,and ultraviolet-visible diffused reflectance spectroscopy(UV-vis DRS)were used to systematically characterize as-obtained materials.Photodegradation of methyl orange in neutral aqueous solutions(pH=6.8)under UV irradiation was studied to evaluate their photocatalytic activities.Morphology,bandgaps,the value of the zero charge point,and photo-catalytic activity of the samples depended on the characteristics of the original silica.The degree of methyl orange degradation reached the maximum values(81%−85%)for samples based on precipitated silica from rice husks,straw,and the minimum value(16%)for a composite with thermal silica from rice straw.Composites based on thermal silica from rice husks and reagents from mineral raw materials did not statistically differ from each other in the degree of methyl orange degradation(67%−74%).展开更多
基金supported by the Institute of Chemistry FEB RAS State Order(Project No.FWFN(205)-2022-0001).
文摘MnWO_(4)/WO_(3) p-n heterojunction films were fabricated using a one-step method consisting of the plasma electrolytic oxidation(PEO)of titanium in homogeneous electrolytes containing paratungstate ions and stable watersoluble EDTA-chelated manganese.The influences of the formation current density and W:Mn molar ratio of the electrolyte,which was varied from 1:2 to 2:1,on the composition,morphology,and optical and photocatalytic properties of the resulting coatings were studied.X-ray diffraction analysis,scanning electron microscopy,energy dispersive X-ray analysis,Raman spectroscopy,and ultraviolet diffuse reflectance spectroscopy were used to characterize the formed composites.Regardless of the W:Mn ratio of the electrolyte,the coatings contained crystalline t-WO_(3) and m-MnWO_(4).Depending on the formation conditions,the optical band gap energies of the composites varied from 2.63 to 3.01 eV.The largest absorption red shift and lowest band gap energy were observed in the film composite formed in an electrolyte with W:Mn=2:1,at a current density of 0.2 A cm^(−2).Composites obtained in electrolytes with W:Mn ratios of 2:1 and 1:1 exhibited photocatalytic activity in the degradation of rhodamine C and methyl orange dyes in the presence of 10 mmol L^(–1) H_(2)O_(2) under ultraviolet and visible light irradiation.The role of hydrogen peroxide in this dye degradation on PEO-coated composites under light irradiation is discussed.
基金a part of the State Order of the Institute of Chemistry of the Far Eastern Branch of the Russian Academy of Sciences,project No.FWFN (0205)-2022-0003support of the Russian Science Foundation (grant No.19-73-10017).
文摘The Bi_(2)O_(3)/Bi_(2)SiO_(5) heterostructures were obtained with various samples of silica as a precursor:on the basis of biogenic silica isolated from rice husk and rice straw and the silica of mineral ori-gin.A mixture of Bi(NO_(3))_(3) and SiO_(2) with a mass content of 15%was used for synthesizing all the samples.Fourier transform infrared(FT-IR)spectroscopy,scanning electron microscope(SEM),X-ray phase,X-ray fluorescence,and ultraviolet-visible diffused reflectance spectroscopy(UV-vis DRS)were used to systematically characterize as-obtained materials.Photodegradation of methyl orange in neutral aqueous solutions(pH=6.8)under UV irradiation was studied to evaluate their photocatalytic activities.Morphology,bandgaps,the value of the zero charge point,and photo-catalytic activity of the samples depended on the characteristics of the original silica.The degree of methyl orange degradation reached the maximum values(81%−85%)for samples based on precipitated silica from rice husks,straw,and the minimum value(16%)for a composite with thermal silica from rice straw.Composites based on thermal silica from rice husks and reagents from mineral raw materials did not statistically differ from each other in the degree of methyl orange degradation(67%−74%).
