Several 2D nanosheets of porphyrin MOFs with various transition-metal clusters as metal nodes were prepared via a simple solvothermal method to apply in the photocatalytic hydrogen evolution,in which the hydrogen prod...Several 2D nanosheets of porphyrin MOFs with various transition-metal clusters as metal nodes were prepared via a simple solvothermal method to apply in the photocatalytic hydrogen evolution,in which the hydrogen production rate of the optimal NS-Cu was as high as 15.39 mmol g^(-1)h^(-1).A series of experimental technologies especially cyclic voltammetry(CV)and Mott-Schottky(M-S)had been adopted to investigate the charge-transfer property of photo-generated electron-hole pairs,it was found that the uniformly dispersed Cu-clusters nodes in the original 2D MOFs played a key role in the electron transfer process,that was,the photo-generated electron transferred from excited state eosin-Y to the Cu-clusters nodes for the efficient hydrogen evolution.The excellent photocatalytic performance could be attributed to the reversible oxidation-–reduction process of Cu^(Ⅱ)/Cu^(Ⅰ),which had excellent electron-receiving and electron-outputting capabilities.Our results provided a novel avenue to adapt the uniformly dispersed metal nodes in the original MOFs as cost-effective noble-metal-free cocatalysts with very high atomutilization efficiency to improve the photocatalytic hydrogen evolution performance in dye-sensitized system.展开更多
Structure,crystallization behavior,and magnetic properties of as-quenched and annealed Fe_(81.3)Si_(4)O_(13)Cu_(1.7)(Cu1.7)alloy ribbons and effects of Nb alloying have been studied.Three-dimensional atom probe and tr...Structure,crystallization behavior,and magnetic properties of as-quenched and annealed Fe_(81.3)Si_(4)O_(13)Cu_(1.7)(Cu1.7)alloy ribbons and effects of Nb alloying have been studied.Three-dimensional atom probe and transmission electron microscopy analyses reveal that high-number-density Cu-clusters and Pre-existing Nano-sized a-Fe Particles(PN-a-Fe)are coexistence in the melt-spun Cu1.7 amorphous matrix,and the PN-α-Fe form by manners of one-direction adjoining and enveloping the Cu-clusters.Two-step crystallization behavior associated with growth of the PN-a-Fe and subsequent nucleation and growth of newly-formedα-Fe is found in the primary crystallization stage of the Cu1.7 alloy.The number densities of the Cu-clusters and PN-a-Fe in melt-spun Fe8_(1.3-x)Si_(4)B_(13)Cu_(1.7)Nb_(x)alloys are gradually reduced with enriching of Nb,and a fully amorphous structure forms at 4 at.%Nb,although smaller Cu-clusters still exist.After annealing,2 at.%Nb coarsens the average size(D_(α-F)e)of theα-Fe grains from 14.0 nm of the Nb-free alloy to 21.6 nm,and 4 at.%Nb refines the D_(α-Fe)to 8.9 nm.The mechanisms of theα-Fe nucleation and growth during quenching and annealing for the alloys with large quantities of PN-α-Fe as well as after Nb alloying have been discussed,and an annealing-induced oc-Fe growth mechanism in term of the barrier co-contributed by competitive growth among the PN-a-Fe and diffusion-suppression effect of Nb atoms has been proposed.A coercivity(HC)αDα-Fe^(3)correlation has been found for the nanocrystalline alloys,and the permeability is inverse with the H_(C).展开更多
基金the National Natural Science Foundation of China(Nos.21502012,22001026)the Youth Project of Science and Technology Research Program of Chongqing Education Commission of China(Nos.KJQN201900838,KJQN201800836,KJQN201900842)+1 种基金the Chongqing Science and Technology Commission(Nos.cstc2018jcyj AX0531,cstc2017jcyj AX0404,cstc2020jcyjmsxm X0830)Student Science and Technology Innovation Fund Project of Chongqing Technology and Business University(No.20328)。
文摘Several 2D nanosheets of porphyrin MOFs with various transition-metal clusters as metal nodes were prepared via a simple solvothermal method to apply in the photocatalytic hydrogen evolution,in which the hydrogen production rate of the optimal NS-Cu was as high as 15.39 mmol g^(-1)h^(-1).A series of experimental technologies especially cyclic voltammetry(CV)and Mott-Schottky(M-S)had been adopted to investigate the charge-transfer property of photo-generated electron-hole pairs,it was found that the uniformly dispersed Cu-clusters nodes in the original 2D MOFs played a key role in the electron transfer process,that was,the photo-generated electron transferred from excited state eosin-Y to the Cu-clusters nodes for the efficient hydrogen evolution.The excellent photocatalytic performance could be attributed to the reversible oxidation-–reduction process of Cu^(Ⅱ)/Cu^(Ⅰ),which had excellent electron-receiving and electron-outputting capabilities.Our results provided a novel avenue to adapt the uniformly dispersed metal nodes in the original MOFs as cost-effective noble-metal-free cocatalysts with very high atomutilization efficiency to improve the photocatalytic hydrogen evolution performance in dye-sensitized system.
基金financially supported by the National Natural Science Foundation of China(Nos.51571047,5177103951871039)the National Key Research and Development Program of China(No.2017YFB0903903)。
文摘Structure,crystallization behavior,and magnetic properties of as-quenched and annealed Fe_(81.3)Si_(4)O_(13)Cu_(1.7)(Cu1.7)alloy ribbons and effects of Nb alloying have been studied.Three-dimensional atom probe and transmission electron microscopy analyses reveal that high-number-density Cu-clusters and Pre-existing Nano-sized a-Fe Particles(PN-a-Fe)are coexistence in the melt-spun Cu1.7 amorphous matrix,and the PN-α-Fe form by manners of one-direction adjoining and enveloping the Cu-clusters.Two-step crystallization behavior associated with growth of the PN-a-Fe and subsequent nucleation and growth of newly-formedα-Fe is found in the primary crystallization stage of the Cu1.7 alloy.The number densities of the Cu-clusters and PN-a-Fe in melt-spun Fe8_(1.3-x)Si_(4)B_(13)Cu_(1.7)Nb_(x)alloys are gradually reduced with enriching of Nb,and a fully amorphous structure forms at 4 at.%Nb,although smaller Cu-clusters still exist.After annealing,2 at.%Nb coarsens the average size(D_(α-F)e)of theα-Fe grains from 14.0 nm of the Nb-free alloy to 21.6 nm,and 4 at.%Nb refines the D_(α-Fe)to 8.9 nm.The mechanisms of theα-Fe nucleation and growth during quenching and annealing for the alloys with large quantities of PN-α-Fe as well as after Nb alloying have been discussed,and an annealing-induced oc-Fe growth mechanism in term of the barrier co-contributed by competitive growth among the PN-a-Fe and diffusion-suppression effect of Nb atoms has been proposed.A coercivity(HC)αDα-Fe^(3)correlation has been found for the nanocrystalline alloys,and the permeability is inverse with the H_(C).
