The hydrogen reduction of tungsten oxides WO_(2.90),W_(20)O_(58) and WO_3 were directly studied using high temperature X-ray diffraction analysis.The differences between tetragonal WO_(2.90) and monoclinic W_(20)O_(58...The hydrogen reduction of tungsten oxides WO_(2.90),W_(20)O_(58) and WO_3 were directly studied using high temperature X-ray diffraction analysis.The differences between tetragonal WO_(2.90) and monoclinic W_(20)O_(58) were discussed.Pure β-W was obtained from oxide WO_(2.90),while there appears small amount of WO_2 during the reduction of W_(20)O_(58) to β-W.展开更多
The hydrogen reduction of tungsten oxides WO_(272)and WO_2 were studied directly using high-temperature X-ray diffraction analysis,The pure β-W was obtained from the reduction of WO_(272)The transformation of β-W to...The hydrogen reduction of tungsten oxides WO_(272)and WO_2 were studied directly using high-temperature X-ray diffraction analysis,The pure β-W was obtained from the reduction of WO_(272)The transformation of β-W to x-W was also studied in both hydrogen and nitrogen.The forming condition of β-W from WO_2 was discussed.Finally.a complete schematic diagram of reduction of tungsten oxides was given in this paper.展开更多
The WO_3/C composite was successfully prepared by calcination of a mixture of WO_3 and g-C_3N_4 at 520 ℃. The as-synthesized samples were analyzed by X-ray diffraction(XRD), electronic differential system(EDS), scann...The WO_3/C composite was successfully prepared by calcination of a mixture of WO_3 and g-C_3N_4 at 520 ℃. The as-synthesized samples were analyzed by X-ray diffraction(XRD), electronic differential system(EDS), scanning electron microscopy(SEM), infrared spectrometry(IR) and the Brunner-Emmet-Teller(BET) techniques. The WO_3/C composite, in comparison with the WO_3 and C_3N_4, features smaller particle size, bigger surface area and higher desulphurization performance. The influence of the reaction temperature, the catalyst dosage, the reaction time, the oxidant dosage, the sulfide type and the extractant dose on desulfurization reaction was studied. The results showed that the WO_3/C composite revealed a higher desulfurization activity than the WO_3. The desulfurization rate could reach up to 95.8% under optimal conditions covering a catalyst dosage of 0.02 g, a H_2O_2 amount of 0.2 mL, a 1-ethyl-3-methylimidazolium ethyl sulfate(EMIES) amount of 1.0 mL, a reaction temperature of 70 ℃ and a reaction time of 180 min. After five recycles, the desulfurization activity of catalyst did not significantly decline.展开更多
Normal photocatalysts cannot effectively remove low-concentration NO because of the high recombination rate of the photogenerated carriers.To overcome this problem,S-scheme composites have been developed to fabricate ...Normal photocatalysts cannot effectively remove low-concentration NO because of the high recombination rate of the photogenerated carriers.To overcome this problem,S-scheme composites have been developed to fabricate photocatalysts.Herein,a novel S-scheme Sb2WO6/g-C3N4 nanocomposite was fabricated by an ultrasound-assisted method,which exhibited excellent performance for photocatalytic ppb-level NO removal.Compared with the pure constituents of the nanocomposite,the as-prepared 15%-Sb2WO6/g-C3N4 photocatalyst could remove more than 68%continuous-flowing NO(initial concentration:400 ppb)under visible-light irradiation in 30 min.The findings of the trapping experiments confirmed that•O2^–and h+were the important active species in the NO oxidation reaction.Meanwhile,the transient photocurrent response and PL spectroscopy analyses proved that the unique S-scheme structure of the samples could enhance the charge separation efficiency.In situ DRIFTS revealed that the photocatalytic reaction pathway of NO removal over the Sb2WO6/g-C3N4 nanocomposite occurred via an oxygen-induced route.The present work proposes a new concept for fabricating efficient photocatalysts for photocatalytic ppb-level NO oxidation and provides deeper insights into the mechanism of photocatalytic NO oxidation.展开更多
Photocatalysis is considered a promising technique for removal of pollutants from indoor air.However,the low selectivity and limited recyclability of photocatalysts in powder form currently limit their practical appli...Photocatalysis is considered a promising technique for removal of pollutants from indoor air.However,the low selectivity and limited recyclability of photocatalysts in powder form currently limit their practical application.In this work,we reported the successful preparation of a monolithic tungsten oxide(WO3)/graphene oxide(GO)aerogel photocatalyst through a cost‐effective freeze‐drying method.GO not only acts as a macroscopic support,but also increases the catalyst surface area from 46 to 57 m2/g,enhances the light absorption in the visible‐light region,and raises the separation efficiency of photogenerated electron‐hole pairs.The Obtained WO3/GO aerogel exhibited an outstanding visible‐light photocatalytic degradation rate of nitric oxide of 51%,which was 3.3 times that of pristine WO3 powder.In addition,the aerogel displayed excellent selectivity,with a generation fraction of toxic nitrogen dioxide of as low as 0.5%.This work presents a facile synthesis route to fabricate a monolithic WO3/GO aerogel photocatalyst with great promise for air purification.展开更多
Z-scheme semiconductors are a promising class of photocatalysts for hydrogen generation.In this work,Z-scheme semiconductors composed of WO3-x quantum dots supported on TiO2（WO3-xQDS/TiO2） were fabricated by solvoth...Z-scheme semiconductors are a promising class of photocatalysts for hydrogen generation.In this work,Z-scheme semiconductors composed of WO3-x quantum dots supported on TiO2（WO3-xQDS/TiO2） were fabricated by solvothermal and hydrogen-reduction methods.Characterization by transmission electron microscopy and X-ray diffraction indicated that the amount and size of the WO3-x QDs could be tuned by modulating the addition of the W precursor.Evidence from X-ray photoelectron spectroscopy and photoluminescence spectroscopy suggested that the hydrogen reduction of the composite induced the formation of oxygen vacancy（W^5＋/Vo） defects in WO3.These defects led to ohmic contact between WO3-x and TiO2,which altered the charge-transfer pathway from type Ⅱ heterojunction to Z-scheme,and maintained the highly reductive and oxidative ability of TiO2 and WO3-x,respectively.Therefore,the Z-scheme sample showed 1.3-fold higher photoactivity than pure TiO2 in hydrogen generation.These results suggest that the formation of W^5＋/Vo defects at the interface is highly beneficial for the fabrication of Z-scheme photocatalysts.展开更多
The polycrystalline phase WO_3/g-C_3N_4 was synthesized under stirring using tungstenic acid(H_2WO_4) and graphitic carbon nitride(g-C_3N_4) as raw materials. The catalyst was characterized by X-ray diffraction(XRD), ...The polycrystalline phase WO_3/g-C_3N_4 was synthesized under stirring using tungstenic acid(H_2WO_4) and graphitic carbon nitride(g-C_3N_4) as raw materials. The catalyst was characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),the Fourier transform infrared spectroscopy(FT-IR),and the Brunauer-Emmett-Teller analysis(BET). The polycrystalline phase WO_3/g-C_3N_4 was determined by XRD technique. The oxidative desulfurization process was investigated using WO_3/g-C_3N_4 as the catalyst, 30% hydrogen peroxide(H202) as the oxidant, and 1-butyl-3-methylimidazolium tetrafluoroborate([bmim]BF4) ionic liquids(ILs) as the extractant. The operating conditions, including H_2WO_4 amount, IL dose, H_2 O_2 volume, temperature, catalyst dosage, and types of sulfur compounds,were systematically researched. The desulfurization rate could reach 98.46% for removing dibenzothiophene(DBT) from the model oil under optimal reaction conditions. In addition, the catalytic activity was slightly decreased after five recycles of catalysts. The reaction kinetics analysis shows that the oxidative desulfurization system was in accord with the first-order reaction kinetics equation. The mechanism of oxidative desulfurization was proposed.展开更多
文摘The hydrogen reduction of tungsten oxides WO_(2.90),W_(20)O_(58) and WO_3 were directly studied using high temperature X-ray diffraction analysis.The differences between tetragonal WO_(2.90) and monoclinic W_(20)O_(58) were discussed.Pure β-W was obtained from oxide WO_(2.90),while there appears small amount of WO_2 during the reduction of W_(20)O_(58) to β-W.
文摘The hydrogen reduction of tungsten oxides WO_(272)and WO_2 were studied directly using high-temperature X-ray diffraction analysis,The pure β-W was obtained from the reduction of WO_(272)The transformation of β-W to x-W was also studied in both hydrogen and nitrogen.The forming condition of β-W from WO_2 was discussed.Finally.a complete schematic diagram of reduction of tungsten oxides was given in this paper.
基金the financial support of the Natural Science Foundation of China (Project No. 21003069)the Liaoning Province Doctoral Fund (Project No.201501105)
文摘The WO_3/C composite was successfully prepared by calcination of a mixture of WO_3 and g-C_3N_4 at 520 ℃. The as-synthesized samples were analyzed by X-ray diffraction(XRD), electronic differential system(EDS), scanning electron microscopy(SEM), infrared spectrometry(IR) and the Brunner-Emmet-Teller(BET) techniques. The WO_3/C composite, in comparison with the WO_3 and C_3N_4, features smaller particle size, bigger surface area and higher desulphurization performance. The influence of the reaction temperature, the catalyst dosage, the reaction time, the oxidant dosage, the sulfide type and the extractant dose on desulfurization reaction was studied. The results showed that the WO_3/C composite revealed a higher desulfurization activity than the WO_3. The desulfurization rate could reach up to 95.8% under optimal conditions covering a catalyst dosage of 0.02 g, a H_2O_2 amount of 0.2 mL, a 1-ethyl-3-methylimidazolium ethyl sulfate(EMIES) amount of 1.0 mL, a reaction temperature of 70 ℃ and a reaction time of 180 min. After five recycles, the desulfurization activity of catalyst did not significantly decline.
文摘Normal photocatalysts cannot effectively remove low-concentration NO because of the high recombination rate of the photogenerated carriers.To overcome this problem,S-scheme composites have been developed to fabricate photocatalysts.Herein,a novel S-scheme Sb2WO6/g-C3N4 nanocomposite was fabricated by an ultrasound-assisted method,which exhibited excellent performance for photocatalytic ppb-level NO removal.Compared with the pure constituents of the nanocomposite,the as-prepared 15%-Sb2WO6/g-C3N4 photocatalyst could remove more than 68%continuous-flowing NO(initial concentration:400 ppb)under visible-light irradiation in 30 min.The findings of the trapping experiments confirmed that•O2^–and h+were the important active species in the NO oxidation reaction.Meanwhile,the transient photocurrent response and PL spectroscopy analyses proved that the unique S-scheme structure of the samples could enhance the charge separation efficiency.In situ DRIFTS revealed that the photocatalytic reaction pathway of NO removal over the Sb2WO6/g-C3N4 nanocomposite occurred via an oxygen-induced route.The present work proposes a new concept for fabricating efficient photocatalysts for photocatalytic ppb-level NO oxidation and provides deeper insights into the mechanism of photocatalytic NO oxidation.
文摘Photocatalysis is considered a promising technique for removal of pollutants from indoor air.However,the low selectivity and limited recyclability of photocatalysts in powder form currently limit their practical application.In this work,we reported the successful preparation of a monolithic tungsten oxide(WO3)/graphene oxide(GO)aerogel photocatalyst through a cost‐effective freeze‐drying method.GO not only acts as a macroscopic support,but also increases the catalyst surface area from 46 to 57 m2/g,enhances the light absorption in the visible‐light region,and raises the separation efficiency of photogenerated electron‐hole pairs.The Obtained WO3/GO aerogel exhibited an outstanding visible‐light photocatalytic degradation rate of nitric oxide of 51%,which was 3.3 times that of pristine WO3 powder.In addition,the aerogel displayed excellent selectivity,with a generation fraction of toxic nitrogen dioxide of as low as 0.5%.This work presents a facile synthesis route to fabricate a monolithic WO3/GO aerogel photocatalyst with great promise for air purification.
基金supported by the National Natural Science Foundation of China (21506156, 21676193)the Tianjin Municipal Natural Science Foundation (15JCZDJC37300, 16JCQNJC05200)~~
文摘Z-scheme semiconductors are a promising class of photocatalysts for hydrogen generation.In this work,Z-scheme semiconductors composed of WO3-x quantum dots supported on TiO2（WO3-xQDS/TiO2） were fabricated by solvothermal and hydrogen-reduction methods.Characterization by transmission electron microscopy and X-ray diffraction indicated that the amount and size of the WO3-x QDs could be tuned by modulating the addition of the W precursor.Evidence from X-ray photoelectron spectroscopy and photoluminescence spectroscopy suggested that the hydrogen reduction of the composite induced the formation of oxygen vacancy（W^5＋/Vo） defects in WO3.These defects led to ohmic contact between WO3-x and TiO2,which altered the charge-transfer pathway from type Ⅱ heterojunction to Z-scheme,and maintained the highly reductive and oxidative ability of TiO2 and WO3-x,respectively.Therefore,the Z-scheme sample showed 1.3-fold higher photoactivity than pure TiO2 in hydrogen generation.These results suggest that the formation of W^5＋/Vo defects at the interface is highly beneficial for the fabrication of Z-scheme photocatalysts.
基金the financial support of the Doctoral Fund of Liaoning Province (201501105)
文摘The polycrystalline phase WO_3/g-C_3N_4 was synthesized under stirring using tungstenic acid(H_2WO_4) and graphitic carbon nitride(g-C_3N_4) as raw materials. The catalyst was characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),the Fourier transform infrared spectroscopy(FT-IR),and the Brunauer-Emmett-Teller analysis(BET). The polycrystalline phase WO_3/g-C_3N_4 was determined by XRD technique. The oxidative desulfurization process was investigated using WO_3/g-C_3N_4 as the catalyst, 30% hydrogen peroxide(H202) as the oxidant, and 1-butyl-3-methylimidazolium tetrafluoroborate([bmim]BF4) ionic liquids(ILs) as the extractant. The operating conditions, including H_2WO_4 amount, IL dose, H_2 O_2 volume, temperature, catalyst dosage, and types of sulfur compounds,were systematically researched. The desulfurization rate could reach 98.46% for removing dibenzothiophene(DBT) from the model oil under optimal reaction conditions. In addition, the catalytic activity was slightly decreased after five recycles of catalysts. The reaction kinetics analysis shows that the oxidative desulfurization system was in accord with the first-order reaction kinetics equation. The mechanism of oxidative desulfurization was proposed.
