Nanoparticulate gold catalysts supported on niobium oxides （Nb2O5） were prepared by different deposition methods. The deposition precipitation （DP） method, DP method with urea, deposition reduction （DR） method a...Nanoparticulate gold catalysts supported on niobium oxides （Nb2O5） were prepared by different deposition methods. The deposition precipitation （DP） method, DP method with urea, deposition reduction （DR） method and one‐pot method were used to prepare a 1 wt%Au/Nb2O5 catalyst. Lay‐ered‐type Nb2O5 synthesized by a hydrothermal method （Nb2O5（HT）） was the most suitable as a support among various types of Nb2O5 including commercially available Nb2O5 samples. It appeared that the large BET surface area of Nb2O5（HT） enabled the dispersion of gold as nanoparticles （NPs）. Gold NPs with a mean diameter of about 5 nm were deposited by both the DP method and DR method on Nb2O5（HT） under an optimized condition. The temperature for 50%CO conversion for Au/Nb2O5（HT） prepared by the DR method was 73 ＆#176;C. Without deposition of gold, Nb2O5（HT） showed no catalytic activity for CO oxidation even at 250 ＆#176;C. Therefore, the enhancement of the activity by deposition of gold was remarkable. This simple Au/Nb2O5 catalyst will expand the types of gold catalysts to acidic supports, giving rise to new applications.展开更多
Oxygen reduction reactions(ORRs)with one-or two-electron-transfer pathways are the essential process for aprotic metal-oxygen batteries,in which the stability of superoxide intermediates/products(O_(2)^(-),LiO_(2),NaO...Oxygen reduction reactions(ORRs)with one-or two-electron-transfer pathways are the essential process for aprotic metal-oxygen batteries,in which the stability of superoxide intermediates/products(O_(2)^(-),LiO_(2),NaO_(2),etc.)mainly dominates the ORR activity/stability and battery performance.However,little success in regulating the stability of the superoxides has been achieved due to their highly reactive characteristics.Herein,we identified and modulated the stability of superoxides by introducing anthraquinone derivatives as cocatalysts which functioned as superoxide trapper adsorbing the superoxides generated via surface-mediated ORR and then transferring them from the solid catalyst surface into electrolyte.Among the studied trappers,1,4-difluoroanthraquinone(DFAQ)with electron-withdrawing groups showed the highest adsorption towards superoxides and could efficiently stabilize LiO_(2)in electrolyte,which greatly promoted the surface-mediated ORR rate and stability.This highlighted the magnitude of adsorption between the trapper and LiO_(2)on the ORR activity/stability.Using an aprotic Li-O_(2)battery as a model metal-O_(2)battery,the overall performance of the cell with DFAQ was substantially improved in terms of cell capacity,rate capability and cyclic stability.These results represent a significant advance in the understanding of ORR mechanisms and promoting the performance of metal-O_(2)batteries.展开更多
文摘Nanoparticulate gold catalysts supported on niobium oxides （Nb2O5） were prepared by different deposition methods. The deposition precipitation （DP） method, DP method with urea, deposition reduction （DR） method and one‐pot method were used to prepare a 1 wt%Au/Nb2O5 catalyst. Lay‐ered‐type Nb2O5 synthesized by a hydrothermal method （Nb2O5（HT）） was the most suitable as a support among various types of Nb2O5 including commercially available Nb2O5 samples. It appeared that the large BET surface area of Nb2O5（HT） enabled the dispersion of gold as nanoparticles （NPs）. Gold NPs with a mean diameter of about 5 nm were deposited by both the DP method and DR method on Nb2O5（HT） under an optimized condition. The temperature for 50%CO conversion for Au/Nb2O5（HT） prepared by the DR method was 73 ＆#176;C. Without deposition of gold, Nb2O5（HT） showed no catalytic activity for CO oxidation even at 250 ＆#176;C. Therefore, the enhancement of the activity by deposition of gold was remarkable. This simple Au/Nb2O5 catalyst will expand the types of gold catalysts to acidic supports, giving rise to new applications.
基金the National Natural Science Foundation of China(21773055,U1604122,51702086,21203055and 21805070)the Program for Science&Technology Innovation Talents in Universities of Henan Province(18HASTIT004)China Postdoctoral Science Foundation(2020M672201)。
文摘Oxygen reduction reactions(ORRs)with one-or two-electron-transfer pathways are the essential process for aprotic metal-oxygen batteries,in which the stability of superoxide intermediates/products(O_(2)^(-),LiO_(2),NaO_(2),etc.)mainly dominates the ORR activity/stability and battery performance.However,little success in regulating the stability of the superoxides has been achieved due to their highly reactive characteristics.Herein,we identified and modulated the stability of superoxides by introducing anthraquinone derivatives as cocatalysts which functioned as superoxide trapper adsorbing the superoxides generated via surface-mediated ORR and then transferring them from the solid catalyst surface into electrolyte.Among the studied trappers,1,4-difluoroanthraquinone(DFAQ)with electron-withdrawing groups showed the highest adsorption towards superoxides and could efficiently stabilize LiO_(2)in electrolyte,which greatly promoted the surface-mediated ORR rate and stability.This highlighted the magnitude of adsorption between the trapper and LiO_(2)on the ORR activity/stability.Using an aprotic Li-O_(2)battery as a model metal-O_(2)battery,the overall performance of the cell with DFAQ was substantially improved in terms of cell capacity,rate capability and cyclic stability.These results represent a significant advance in the understanding of ORR mechanisms and promoting the performance of metal-O_(2)batteries.
