Fuel cell stacks as the automotive power source can be severely poisoned by a trace amount of NOx in atmosphere,which makes it necessary to provide clean air for fuel cell vehicles.In this work,activating commercial a...Fuel cell stacks as the automotive power source can be severely poisoned by a trace amount of NOx in atmosphere,which makes it necessary to provide clean air for fuel cell vehicles.In this work,activating commercial activated carbons with K2CO3 for the large enhancement of NO capture was studied.K2CO3 modified activated carbons(K2CO3 ACs)were prepared by impregnating activate carbons in K2CO3 solution under ultrasound treatment,followed by temperature programmed baking at 800 oC.The dynamic NO flow tests on K2CO3 ACs at room temperature indicated that NO adsorption capacity reached the maximum(96 mg/g)when K2CO3 loading was 19.5 wt%,which corresponded to a specific surface area of 1196.1 m2/g and total pore volume of 0.70 cm3/g.The ten-fold enhancement of NO adsorption on K2CO3 ACs compared to the unimpregnated activated carbon was mainly attributed to the formation of potassium nitrite,which was confirmed by FTIR and temperature programmed desorption measurements.Regeneration tests of NO adsorption on the optimum sample revealed that 76%of the NO adsorption capacity could be remained after the fourth cycle.展开更多
Study of physisorbed and chemisorbed carbon dioxide (CO<sub>2</sub>) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca<sup>2+</sup> and Ba<s...Study of physisorbed and chemisorbed carbon dioxide (CO<sub>2</sub>) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca<sup>2+</sup> and Ba<sup>2+</sup>) by temperature-programmed desorption of CO<sub>2</sub> (CO<sub>2</sub>-TPD). Others results were obtained by infrared to complete the study. The results of this research showed, in the physisorption region (213 - 473 K), that the cationic exchanges on NaX zeolite with bivalent cations increase slightly the interactions of CO<sub>2</sub> molecule with adsorbents and/or cationic site. Indeed, the desorption energies of physisorbed CO<sub>2</sub> obtained on the reference zeolite NaX (13.5 kJ·mol<sup>-1</sup>) are lower than that of exchanged zeolites E-CaX and E-BaX (15.77 and 15.17 kJ·mol<sup>-1</sup> respectively). In the chemisorbed CO<sub>2</sub> region (573 - 873 K), the desorption energies related to desorbed species (bidentate carbonates: CO<sub>3</sub>2-</sup>) on the exchanged zeolites E-CaX and E-BaX are about 81 kJ·mol<sup>-1</sup>, higher than the desorbed species (bicarbonates: HCO<sub>3</sub>2-</sup>) on the reference R-NaX (62 kJ·mol<sup>-1</sup>). In addition, the exchanged E-BaX zeolite develops the secondary adsorption sites corresponding to bicarbonates species with desorption energies of 35 kJ·mol<sup>-1</sup> lower to desorption energies of bicarbonates noted on the reference zeolite NaX.展开更多
The activity and adsorption behavior of oxygen on rutile TiO_(2)(110)(RTiO_(2)(110))were investigated using the temperature programmed desorption(TPD)method with methanol(CH_(3)OH)as the probe molecule.By controlling ...The activity and adsorption behavior of oxygen on rutile TiO_(2)(110)(RTiO_(2)(110))were investigated using the temperature programmed desorption(TPD)method with methanol(CH_(3)OH)as the probe molecule.By controlling the coverage of molecular O_(2)on the surface via increasing or decreasing O_(2)exposure,two chemisorbed O_(2)species on the surface are confirmed,one at the bridging oxygen vacancy(Ov)site(O_(2)^(2-)/Ov)and the other at the five-fold coordinated titanium(Ti_(5c))site(O^(2-)/Ti_(5c)).At low O_(2)exposure,O^(2-)/Ov is the main species on the surface,which only leads to the O-H bond cleavage of CH_(3)OH,producing methoxy groups(CHgO).However,after the Ov sites are nearly filled by O_(2)at about 0.1 L O_(2)exposure,O_(2)/Tisc species begins to appear on R-TiO_(2)(110)surface,resulting in the formation of formaldehyde(CH_(2)O)via the reaction of O_(2)/Tisc species with CH_(3)OH or CH3O to break the C-H bond at low surface temperature.Moreover,the yield of CH_(2)O increases linearly with that of H_(2)O.In addition,when the 1 L O_(2)covered surface is irradiated with 355 nm UV irradiation to desorb and dissociate O_(2)/Ti_(5c)species,the yield of CH_(2)O decreases linearly with that of H_(2)O.Further analysis suggests that the charge state of O_(2)/Ti_(5c)may not change as the exposure of O_(2)changes on the R-TiO_(2)(110)surface,and O_(2)is most likely to adsorb on the Ti_(5c)sites in the form of O_(2)^(2-),not O_(2)^(-),The result not only advances our understanding on the adsorption state of O_(2)on TiO_(2),but also provides clues for low temperature C-H bond activation with O_(2)on TiO_(2).展开更多
Pt Sn/MgAl 2O 4 catalysts prepared by co impregnation with nominal 0 35% platinum and varying content of tin (0～2 5%) were characterized by temperature programmed reduction (TPR) and temperature programmed desorption...Pt Sn/MgAl 2O 4 catalysts prepared by co impregnation with nominal 0 35% platinum and varying content of tin (0～2 5%) were characterized by temperature programmed reduction (TPR) and temperature programmed desorption of hydrogen (H 2 TPD). TPR results showed that platinum catalyzed the reduction of tin. However, the average oxidation state of tin after reduction depended upon the concentration of tin on the catalysts. H 2 TPD data indicated that tin addition inhibited the inactivated adsorption of hydrogen but promoted the activated adsorption, implying that tin modified both the ensembles of platinum and metal support interface, thus increasing hydrogen mobility and promoting hydrogen spillover.展开更多
基金Project(2018YFB0105303)supported by the Ministry of Science and Technology of ChinaProject(17DZ1200702)supported by the Shanghai Science and Technology Committee,China
文摘Fuel cell stacks as the automotive power source can be severely poisoned by a trace amount of NOx in atmosphere,which makes it necessary to provide clean air for fuel cell vehicles.In this work,activating commercial activated carbons with K2CO3 for the large enhancement of NO capture was studied.K2CO3 modified activated carbons(K2CO3 ACs)were prepared by impregnating activate carbons in K2CO3 solution under ultrasound treatment,followed by temperature programmed baking at 800 oC.The dynamic NO flow tests on K2CO3 ACs at room temperature indicated that NO adsorption capacity reached the maximum(96 mg/g)when K2CO3 loading was 19.5 wt%,which corresponded to a specific surface area of 1196.1 m2/g and total pore volume of 0.70 cm3/g.The ten-fold enhancement of NO adsorption on K2CO3 ACs compared to the unimpregnated activated carbon was mainly attributed to the formation of potassium nitrite,which was confirmed by FTIR and temperature programmed desorption measurements.Regeneration tests of NO adsorption on the optimum sample revealed that 76%of the NO adsorption capacity could be remained after the fourth cycle.
文摘Study of physisorbed and chemisorbed carbon dioxide (CO<sub>2</sub>) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca<sup>2+</sup> and Ba<sup>2+</sup>) by temperature-programmed desorption of CO<sub>2</sub> (CO<sub>2</sub>-TPD). Others results were obtained by infrared to complete the study. The results of this research showed, in the physisorption region (213 - 473 K), that the cationic exchanges on NaX zeolite with bivalent cations increase slightly the interactions of CO<sub>2</sub> molecule with adsorbents and/or cationic site. Indeed, the desorption energies of physisorbed CO<sub>2</sub> obtained on the reference zeolite NaX (13.5 kJ·mol<sup>-1</sup>) are lower than that of exchanged zeolites E-CaX and E-BaX (15.77 and 15.17 kJ·mol<sup>-1</sup> respectively). In the chemisorbed CO<sub>2</sub> region (573 - 873 K), the desorption energies related to desorbed species (bidentate carbonates: CO<sub>3</sub>2-</sup>) on the exchanged zeolites E-CaX and E-BaX are about 81 kJ·mol<sup>-1</sup>, higher than the desorbed species (bicarbonates: HCO<sub>3</sub>2-</sup>) on the reference R-NaX (62 kJ·mol<sup>-1</sup>). In addition, the exchanged E-BaX zeolite develops the secondary adsorption sites corresponding to bicarbonates species with desorption energies of 35 kJ·mol<sup>-1</sup> lower to desorption energies of bicarbonates noted on the reference zeolite NaX.
基金This work was supported by the National Natural Science Foundation of China(No.21973010)Liaoning Revitalization Talents Program(No.XLYC1907032)The authors thank Qing Guo at Southern University of Science and Technolog for many insightful discussions。
文摘The activity and adsorption behavior of oxygen on rutile TiO_(2)(110)(RTiO_(2)(110))were investigated using the temperature programmed desorption(TPD)method with methanol(CH_(3)OH)as the probe molecule.By controlling the coverage of molecular O_(2)on the surface via increasing or decreasing O_(2)exposure,two chemisorbed O_(2)species on the surface are confirmed,one at the bridging oxygen vacancy(Ov)site(O_(2)^(2-)/Ov)and the other at the five-fold coordinated titanium(Ti_(5c))site(O^(2-)/Ti_(5c)).At low O_(2)exposure,O^(2-)/Ov is the main species on the surface,which only leads to the O-H bond cleavage of CH_(3)OH,producing methoxy groups(CHgO).However,after the Ov sites are nearly filled by O_(2)at about 0.1 L O_(2)exposure,O_(2)/Tisc species begins to appear on R-TiO_(2)(110)surface,resulting in the formation of formaldehyde(CH_(2)O)via the reaction of O_(2)/Tisc species with CH_(3)OH or CH3O to break the C-H bond at low surface temperature.Moreover,the yield of CH_(2)O increases linearly with that of H_(2)O.In addition,when the 1 L O_(2)covered surface is irradiated with 355 nm UV irradiation to desorb and dissociate O_(2)/Ti_(5c)species,the yield of CH_(2)O decreases linearly with that of H_(2)O.Further analysis suggests that the charge state of O_(2)/Ti_(5c)may not change as the exposure of O_(2)changes on the R-TiO_(2)(110)surface,and O_(2)is most likely to adsorb on the Ti_(5c)sites in the form of O_(2)^(2-),not O_(2)^(-),The result not only advances our understanding on the adsorption state of O_(2)on TiO_(2),but also provides clues for low temperature C-H bond activation with O_(2)on TiO_(2).
文摘Pt Sn/MgAl 2O 4 catalysts prepared by co impregnation with nominal 0 35% platinum and varying content of tin (0～2 5%) were characterized by temperature programmed reduction (TPR) and temperature programmed desorption of hydrogen (H 2 TPD). TPR results showed that platinum catalyzed the reduction of tin. However, the average oxidation state of tin after reduction depended upon the concentration of tin on the catalysts. H 2 TPD data indicated that tin addition inhibited the inactivated adsorption of hydrogen but promoted the activated adsorption, implying that tin modified both the ensembles of platinum and metal support interface, thus increasing hydrogen mobility and promoting hydrogen spillover.
