The evolution of the S'precipitate in Al−Cu−Mg alloy was investigated using transmission electron microscopy(TEM),high-angle annular dark-field scanning transmission electron microscopy(HAADF−STEM),molecular dynam...The evolution of the S'precipitate in Al−Cu−Mg alloy was investigated using transmission electron microscopy(TEM),high-angle annular dark-field scanning transmission electron microscopy(HAADF−STEM),molecular dynamics(MD)simulations,and other analytical techniques.The precipitation behavior during different aging stages of the supersaturated solid solution formed after rapid cold punching was focused,which induces rapid dissolution of precipitates.The findings reveal that the precipitation sequence is significantly influenced by aging temperature.At higher aging temperatures,which mitigate lattice distortion in the matrix,the precipitation sequence follows the conventional path.Conversely,at lower aging temperatures,where lattice distortion persists,the sequence deviates,suppressing the formation of Guinier−Preston−Bagaryatsky(GPB)zones.MD simulations confirm that the variations in solute atom diffusion rates at different aging temperatures lead to the differences in the S'phase precipitation sequence.展开更多
Reverse water-gas shift(RWGS) reaction-aided sustainable CO_(2) conversion has emerged as one promising and effective approach for simultaneously mitigating climate change and solidifying energy security.Molybdenum ca...Reverse water-gas shift(RWGS) reaction-aided sustainable CO_(2) conversion has emerged as one promising and effective approach for simultaneously mitigating climate change and solidifying energy security.Molybdenum carbide-based catalysts demonstrate excellent selectivity for sustainably transforming CO_(2) into CO product,but harsh carburization syntheses and insufficient catalytic activity and stability significantly hinder their related commercial applications.Herein,a facile "insideout" synthesis strategy was proposed to fabricate dispersed Cu clusters on sub-2 nm α-MoC nanoislands confined in pyridinic nitrogen-doped carbon(Cu-MoC/NC).This catalyst achieves the highest CO_(2) conversion rate of 2583.4 mmol_(CO_(2)) g_(cat)^(-1) h^(-1)compared to those of all reported Mo-based catalysts,and maintains excellent catalytic stability for 500 h under a low H_(2) partial pressure.Combined with X-ray absorption spectroscopy(XAS) and density functional theory(DFT) calculations,the electronegativity of pyridinic nitrogen intensifies the electron deficiency of α-MoC and strengthens the chemisorption of Cu clusters on α-MoC nanoislands surface,facilitating the electronic interaction and stability of Cu-MoC interface.This pyridinic nitrogenmodified Cu-MoC interface promotes the CO_(2) bridged adsorption at the interface and thus boosts C=O bond scissoring,inducing the transition of rate-limiting step and energy barrier reduction of the key intermediates.This interfacial engineering provides a sustainable and efficient strategy for improving both catalytic activity and stability of RWGS reaction to transform CO_(2) into value-added fuels and chemicals.展开更多
基金supported by the China Scholarship Council (CSC) Local Cooperation Program (No. 202308430176)the National Natural Science Foundation of China (No. 52271177)the Hunan Provincial Natural Science Foundation Regional Joint Fund, China (No. 2023JJ50173)。
文摘The evolution of the S'precipitate in Al−Cu−Mg alloy was investigated using transmission electron microscopy(TEM),high-angle annular dark-field scanning transmission electron microscopy(HAADF−STEM),molecular dynamics(MD)simulations,and other analytical techniques.The precipitation behavior during different aging stages of the supersaturated solid solution formed after rapid cold punching was focused,which induces rapid dissolution of precipitates.The findings reveal that the precipitation sequence is significantly influenced by aging temperature.At higher aging temperatures,which mitigate lattice distortion in the matrix,the precipitation sequence follows the conventional path.Conversely,at lower aging temperatures,where lattice distortion persists,the sequence deviates,suppressing the formation of Guinier−Preston−Bagaryatsky(GPB)zones.MD simulations confirm that the variations in solute atom diffusion rates at different aging temperatures lead to the differences in the S'phase precipitation sequence.
基金National Natural Science Foundation of China,Grant/Award Number:42377249,52476183National Key Research and Development Program of China,Grant/Award Number:2023YFD2201605。
文摘Reverse water-gas shift(RWGS) reaction-aided sustainable CO_(2) conversion has emerged as one promising and effective approach for simultaneously mitigating climate change and solidifying energy security.Molybdenum carbide-based catalysts demonstrate excellent selectivity for sustainably transforming CO_(2) into CO product,but harsh carburization syntheses and insufficient catalytic activity and stability significantly hinder their related commercial applications.Herein,a facile "insideout" synthesis strategy was proposed to fabricate dispersed Cu clusters on sub-2 nm α-MoC nanoislands confined in pyridinic nitrogen-doped carbon(Cu-MoC/NC).This catalyst achieves the highest CO_(2) conversion rate of 2583.4 mmol_(CO_(2)) g_(cat)^(-1) h^(-1)compared to those of all reported Mo-based catalysts,and maintains excellent catalytic stability for 500 h under a low H_(2) partial pressure.Combined with X-ray absorption spectroscopy(XAS) and density functional theory(DFT) calculations,the electronegativity of pyridinic nitrogen intensifies the electron deficiency of α-MoC and strengthens the chemisorption of Cu clusters on α-MoC nanoislands surface,facilitating the electronic interaction and stability of Cu-MoC interface.This pyridinic nitrogenmodified Cu-MoC interface promotes the CO_(2) bridged adsorption at the interface and thus boosts C=O bond scissoring,inducing the transition of rate-limiting step and energy barrier reduction of the key intermediates.This interfacial engineering provides a sustainable and efficient strategy for improving both catalytic activity and stability of RWGS reaction to transform CO_(2) into value-added fuels and chemicals.
