Catalytic reduction of nitrate over bimetallic catalysts has emerged as a technology for sustainable treatment of nitrate-containing groundwater.However,the structure of bimetallic has been much less investigated for ...Catalytic reduction of nitrate over bimetallic catalysts has emerged as a technology for sustainable treatment of nitrate-containing groundwater.However,the structure of bimetallic has been much less investigated for catalyst optimization.Herein,two main types of Pd-Cu bimetallic nanocrystal structures,heterostructure and intermetallic,were prepared and characterized using high-resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The results show that two individual Pd and Cu nanocrystals with a mixed interface exist in the heterostructure nanocrystals,while Pd and Cu atoms are uniformly distributed across the intermetallic Pd-Cu nanocrystals.The catalytic nitrate reduction experiments were carried out in a semibatch reactor under constant hydrogen flow.The nitrate conversion rate of the heterostructure Pd-Cu nanocrystals supported onα-Al_(2)O_(3),γ-Al_(2)O_(3),SBA-15,and XC-72R exhibited 3.82-,6.76-,4.28-,2.44-fold enhancements relative to the intermetallic nanocrystals,and the nitrogen and nitrite were the main products for the heterostructure and intermetallic Pd-Cu nanocrystals,respectively.This indicates that the catalytic nitrate reduction over Pd-Cu catalyst is sensitive to the bimetallic structures of the catalysts,and heterostructure bimetallic nanocrystals exhibit better catalytic performances on both the activity and selectivity,which may provide new insights into the design and optimization of catalysts to improve catalytic activity and selectivity for nitrate reduction in water.展开更多
Nano-particle Pd/?-Al2O3 monometallic and Pd-Cu/?-Al2O3 bimetall ic catalysts were prepared by solvated metal atom impregnation (SMAI) method. Th e results of XRD measurement indicated that Pd- Cu alloy was formed in ...Nano-particle Pd/?-Al2O3 monometallic and Pd-Cu/?-Al2O3 bimetall ic catalysts were prepared by solvated metal atom impregnation (SMAI) method. Th e results of XRD measurement indicated that Pd- Cu alloy was formed in the bim etallic catalysts and the crystalline particle size of the alloy increased as Cu contents increased with average diameters < 6.0nm for all the samples. XPS and Auger spectra showed that Pd was in zero- valent state, Cu existed mainly in z ero- valent state and partially in monovalent state Cu+. The Pd/?-Al2O3 and Pd-Cu/?-Al2O3 catalysts exhibited higher activity for CO oxidation at low temperature. The activity of Pd-Cu/?-Al2O3 bimetallic catalyst was hig her than that of Pd/?-Al2O3 monometallic catalyst. The Pd-Cu/?-Al2O3 c atalyst with Pd/Cu atomic ratio of 1∶1 showed the highest activity.展开更多
基金support from the National Natural Science Foundation of China(Nos.52370100,52000146,and 51978098)China Postdoctoral Science Foundation(No.2020M673351).
文摘Catalytic reduction of nitrate over bimetallic catalysts has emerged as a technology for sustainable treatment of nitrate-containing groundwater.However,the structure of bimetallic has been much less investigated for catalyst optimization.Herein,two main types of Pd-Cu bimetallic nanocrystal structures,heterostructure and intermetallic,were prepared and characterized using high-resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The results show that two individual Pd and Cu nanocrystals with a mixed interface exist in the heterostructure nanocrystals,while Pd and Cu atoms are uniformly distributed across the intermetallic Pd-Cu nanocrystals.The catalytic nitrate reduction experiments were carried out in a semibatch reactor under constant hydrogen flow.The nitrate conversion rate of the heterostructure Pd-Cu nanocrystals supported onα-Al_(2)O_(3),γ-Al_(2)O_(3),SBA-15,and XC-72R exhibited 3.82-,6.76-,4.28-,2.44-fold enhancements relative to the intermetallic nanocrystals,and the nitrogen and nitrite were the main products for the heterostructure and intermetallic Pd-Cu nanocrystals,respectively.This indicates that the catalytic nitrate reduction over Pd-Cu catalyst is sensitive to the bimetallic structures of the catalysts,and heterostructure bimetallic nanocrystals exhibit better catalytic performances on both the activity and selectivity,which may provide new insights into the design and optimization of catalysts to improve catalytic activity and selectivity for nitrate reduction in water.
文摘Nano-particle Pd/?-Al2O3 monometallic and Pd-Cu/?-Al2O3 bimetall ic catalysts were prepared by solvated metal atom impregnation (SMAI) method. Th e results of XRD measurement indicated that Pd- Cu alloy was formed in the bim etallic catalysts and the crystalline particle size of the alloy increased as Cu contents increased with average diameters < 6.0nm for all the samples. XPS and Auger spectra showed that Pd was in zero- valent state, Cu existed mainly in z ero- valent state and partially in monovalent state Cu+. The Pd/?-Al2O3 and Pd-Cu/?-Al2O3 catalysts exhibited higher activity for CO oxidation at low temperature. The activity of Pd-Cu/?-Al2O3 bimetallic catalyst was hig her than that of Pd/?-Al2O3 monometallic catalyst. The Pd-Cu/?-Al2O3 c atalyst with Pd/Cu atomic ratio of 1∶1 showed the highest activity.
