Pt/ZrO2catalysts promoted with MoO3and Nb2O5were tested for the combustion of short-chain alkanes(namely,methane,ethane,propane,and n-hexane).For short-chain alkane combustion,the inhibition of MoO3(for...Pt/ZrO2catalysts promoted with MoO3and Nb2O5were tested for the combustion of short-chain alkanes(namely,methane,ethane,propane,and n-hexane).For short-chain alkane combustion,the inhibition of MoO3(for the methane reaction)dramatically transformed to promotion(for the ethane,propane,and n-hexane reactions)as the carbon chain length increased,whereas the remarkable promotion of Nb2O5gradually weakened with an increase in the carbon chain length.Based on a detailed study of the oxidation reactions of methane and propane over the catalysts,the different roles of the promoters in the reactions were ascribed to differences in the acidic properties of the surface and the oxidation or reduction states of the Pt species.The MoO3promoter could decorate the surface of the Pt species for a Pt-Mo/ZrO2catalyst,whereas the Nb2O5promoter on the support could be partially covered by Pt particles for a Pt-Nb/ZrO2catalyst.The formation of accessible Pt-MoO3interfacial sites,a high concentration of metallic Pt species,and a high surface acidity in Pt-Mo/ZrO2were responsible for the enhanced activity for catalytic propane combustion.The lack of enough accessible Pt-Nb2O5interfacial sites but an enhanced surface acid sites in Pt-Nb/ZrO2explained the slight improvement in activity for catalytic propane combustion.However,the stabilized Ptn+species in Pt-Nb/ZrO2were responsible for the much-improved activity for methane combustion,whereas the Ptn+species in Pt-Mo/ZrO2could be reduced during the oxidation reaction,and the fewer exposed surface Pt species because of MoO3decoration accounted for the inhibited activity for methane combustion.In addition,it can be concluded that MoO3promotion is favorable for the activation of C-C bonds,whereas Nb2O5promotion is more beneficial for the activation of C-H bonds with high energy.展开更多
The surface plasmonic resonance(SPR)effect of Bi can effectively improve the light absorption abilities and photogenerated charge carrier separation rate.In this study,a novel ternary heterojunction of g-C3N4/Bi2MoO6/...The surface plasmonic resonance(SPR)effect of Bi can effectively improve the light absorption abilities and photogenerated charge carrier separation rate.In this study,a novel ternary heterojunction of g-C3N4/Bi2MoO6/Bi(CN/BMO/Bi)hollow microsphere was successfully fabricated through solvothermal and in situ reduction methods.The results revealed that the optimal ternary 0.4 CN/BMO/9 Bi photocatalyst exhibited the highest photocatalytic efficiency toward rhodamine B(RhB)degradation with nine times that of pure BMO.The DRS and valence band of the X-ray photoelectron spectroscopy spectrum demonstrate that the band structure of 0.4 CN/BMO/9 Bi is a z-scheme structure.Quenching experiments also provided solid evidence that the·O^2-(at-0.33 eV)is the main species during dye degradation,and the conduction band of g-C3N4 is only the reaction site,demonstrating that the transfer of photogenerated charge carriers of g-C3N4/Bi2 MoO 6/Bi is through an indirect z-scheme structure.Thus,the enhanced photocatalytic performance was mainly ascribed to the synergetic effect of heterojunction structures between g-C3N4 and Bi2MoO6 and the SPR effect of Bi doping,resulting in better optical absorption ability and a lower combination rate of photogenerated charge carriers.The findings in this work provide insight into the synergism of heterostructures and the SPR absorption ability in wastewater treatment.展开更多
In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) st...In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.展开更多
In this paper, methane coupling at ambient temperature, under atmospheric pressure and in the presence of hydrogen was firstly investigated by using pulse corona plasma and Pt/g-Al2O3 catalyst. Experimental results sh...In this paper, methane coupling at ambient temperature, under atmospheric pressure and in the presence of hydrogen was firstly investigated by using pulse corona plasma and Pt/g-Al2O3 catalyst. Experimental results showed that Pt/g-Al2O3 catalyst has catalytic activity for methane coupling to C2H4. Over sixty percent of outcomes of C2 hydrocarbons were detected to be ethylene.展开更多
摘要Pt/ZrO2catalysts promoted with MoO3and Nb2O5were tested for the combustion of short-chain alkanes(namely,methane,ethane,propane,and n-hexane).For short-chain alkane combustion,the inhibition of MoO3(for the methane reaction)dramatically transformed to promotion(for the ethane,propane,and n-hexane reactions)as the carbon chain length increased,whereas the remarkable promotion of Nb2O5gradually weakened with an increase in the carbon chain length.Based on a detailed study of the oxidation reactions of methane and propane over the catalysts,the different roles of the promoters in the reactions were ascribed to differences in the acidic properties of the surface and the oxidation or reduction states of the Pt species.The MoO3promoter could decorate the surface of the Pt species for a Pt-Mo/ZrO2catalyst,whereas the Nb2O5promoter on the support could be partially covered by Pt particles for a Pt-Nb/ZrO2catalyst.The formation of accessible Pt-MoO3interfacial sites,a high concentration of metallic Pt species,and a high surface acidity in Pt-Mo/ZrO2were responsible for the enhanced activity for catalytic propane combustion.The lack of enough accessible Pt-Nb2O5interfacial sites but an enhanced surface acid sites in Pt-Nb/ZrO2explained the slight improvement in activity for catalytic propane combustion.However,the stabilized Ptn+species in Pt-Nb/ZrO2were responsible for the much-improved activity for methane combustion,whereas the Ptn+species in Pt-Mo/ZrO2could be reduced during the oxidation reaction,and the fewer exposed surface Pt species because of MoO3decoration accounted for the inhibited activity for methane combustion.In addition,it can be concluded that MoO3promotion is favorable for the activation of C-C bonds,whereas Nb2O5promotion is more beneficial for the activation of C-H bonds with high energy.
基金financially supported by the Science Foundation of China University of Petroleum,Beijing(2462017YJRC048,2462018BJC005)the National Natural Science Foundation of China(51802351)~~
摘要The surface plasmonic resonance(SPR)effect of Bi can effectively improve the light absorption abilities and photogenerated charge carrier separation rate.In this study,a novel ternary heterojunction of g-C3N4/Bi2MoO6/Bi(CN/BMO/Bi)hollow microsphere was successfully fabricated through solvothermal and in situ reduction methods.The results revealed that the optimal ternary 0.4 CN/BMO/9 Bi photocatalyst exhibited the highest photocatalytic efficiency toward rhodamine B(RhB)degradation with nine times that of pure BMO.The DRS and valence band of the X-ray photoelectron spectroscopy spectrum demonstrate that the band structure of 0.4 CN/BMO/9 Bi is a z-scheme structure.Quenching experiments also provided solid evidence that the·O^2-(at-0.33 eV)is the main species during dye degradation,and the conduction band of g-C3N4 is only the reaction site,demonstrating that the transfer of photogenerated charge carriers of g-C3N4/Bi2 MoO 6/Bi is through an indirect z-scheme structure.Thus,the enhanced photocatalytic performance was mainly ascribed to the synergetic effect of heterojunction structures between g-C3N4 and Bi2MoO6 and the SPR effect of Bi doping,resulting in better optical absorption ability and a lower combination rate of photogenerated charge carriers.The findings in this work provide insight into the synergism of heterostructures and the SPR absorption ability in wastewater treatment.
基金the National Natural Science Foundation of China (51676090)the Natural Science Foundation of Jiangsu Province (BK20150513), and the Six Talent Peaks Project in Jiangsu Province.
摘要In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.
摘要In this paper, methane coupling at ambient temperature, under atmospheric pressure and in the presence of hydrogen was firstly investigated by using pulse corona plasma and Pt/g-Al2O3 catalyst. Experimental results showed that Pt/g-Al2O3 catalyst has catalytic activity for methane coupling to C2H4. Over sixty percent of outcomes of C2 hydrocarbons were detected to be ethylene.