Composites of SmCo5-FeNi and SmCo5-FeCo, hard-soft magnetic materials, have been synthesized via electroless plating of magnetically hard SmCo5 powder particles with magnetically soft FeNi and FeCo, respectively. The ...Composites of SmCo5-FeNi and SmCo5-FeCo, hard-soft magnetic materials, have been synthesized via electroless plating of magnetically hard SmCo5 powder particles with magnetically soft FeNi and FeCo, respectively. The influence of coating thickness of soft magnetic layers on the structure and magnetic properties of the composite has been studied. Overall FeNi coating was found to be less dense compared to FeCo for the same plating duration. Structurally the coat ing was found to be nodular in morphology. These coating have dramatic effect on the overall magnetic property of the composite. As compared to FeNi coated SmCo5 composite, two-fold increase in the saturation magnetization has been observed upon coating SmCo5 (Ms^28 emu/g) with FeCo to a value 56 emu/g. The coercivity of composite powder was found to decrease with increasing the coating layer thickness. The absence of exchange spring behavior in the hard-soft composite is attributed to magnetically soft layer thickness exceeding the theoretical length limit for exchange-spring coupling.展开更多
In ZnIn_(2)S_(4)-based photocatalytic systems,structural optimization and compositional regulation are crucial for significantly enhancing hydrogen production performance.Atom doping and heterostructure formation have...In ZnIn_(2)S_(4)-based photocatalytic systems,structural optimization and compositional regulation are crucial for significantly enhancing hydrogen production performance.Atom doping and heterostructure formation have been shown to improve solar energy conversion efficiency,thereby boosting photocatalytic performance.However,to date,no one-step synthesis method has been reported that simultaneously constructs hollow heterostructures and introduces heteroatom doping into ZnIn_(2)S_(4)photocatalysts,primarily due to the absence of suitable templates or synthesis strategies.In this study,we propose a novel one-step,coordination-selective strategy based on the hard-soft acid-base theory,using MOF(Ti)as a structure-directing template.By incorporating Ce^(3+),Zn^(2+),In^(3+),and S^(2-),the MOF(Ti)is successfully converted into a hollow MOF(Ce)structure,while Ce-doped ZnIn_(2)S_(4)nanosheets nucleates on its surface.This process yields a highly active 2D/3D hollow core-shell heterojunction photocatalyst,Ce-ZnIn_(2)S_(4)/MOF(Ce).Both theoretical and experimental results demonstrate that this unique structure significantly enhances charge separation and extends the charge carrier's lifetime,leading to markedly improved photocatalytic hydrogen evolution performance.This work offers an innovative and controllable approach for synthesizing MOF-derived hollow core-shell heterojunctions,paving the way for a highly efficient water-splitting system.展开更多
The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these c...The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these catalysts were buried in the carbon matrix,resulting in a low metal utilization and inaccessibility for adsorption of reactants during the catalytic process.Herein,we reported a facile synthesis based on the hard-soft acid-base(HSAB)theory to fabricate Co single-atom catalysts with highly exposed metal atoms ligated to the external pyridinic-N sites of a nitrogen-doped carbon support.Benefiting from the highly accessible Co active sites,the prepared Co−N−C SAC exhibited a superior oxygen reduction reactivity comparable to that of the commercial Pt/C catalyst,showing a high turnover frequency(TOF)of 0.93 e^(−)·s^(-1)·site^(-1)at 0.85 V vs.RHE,far exceeding those of some representative SACs with a ultra-high metal content.This work provides a rational strategy to design and prepare M−N−C single-atom catalysts featured with high site-accessibility and site-density.展开更多
文摘Composites of SmCo5-FeNi and SmCo5-FeCo, hard-soft magnetic materials, have been synthesized via electroless plating of magnetically hard SmCo5 powder particles with magnetically soft FeNi and FeCo, respectively. The influence of coating thickness of soft magnetic layers on the structure and magnetic properties of the composite has been studied. Overall FeNi coating was found to be less dense compared to FeCo for the same plating duration. Structurally the coat ing was found to be nodular in morphology. These coating have dramatic effect on the overall magnetic property of the composite. As compared to FeNi coated SmCo5 composite, two-fold increase in the saturation magnetization has been observed upon coating SmCo5 (Ms^28 emu/g) with FeCo to a value 56 emu/g. The coercivity of composite powder was found to decrease with increasing the coating layer thickness. The absence of exchange spring behavior in the hard-soft composite is attributed to magnetically soft layer thickness exceeding the theoretical length limit for exchange-spring coupling.
基金supported by the National Natural Science Foundation of China(22221001,22131007,22401119)the Science and Technology Major Plan of Gansu Province(23ZDGA012,24JRRA435)+1 种基金the 111 Project(B20027)the Fundamental Research Funds for the Central Universities(lzujbky-2024-jdzx13)。
文摘In ZnIn_(2)S_(4)-based photocatalytic systems,structural optimization and compositional regulation are crucial for significantly enhancing hydrogen production performance.Atom doping and heterostructure formation have been shown to improve solar energy conversion efficiency,thereby boosting photocatalytic performance.However,to date,no one-step synthesis method has been reported that simultaneously constructs hollow heterostructures and introduces heteroatom doping into ZnIn_(2)S_(4)photocatalysts,primarily due to the absence of suitable templates or synthesis strategies.In this study,we propose a novel one-step,coordination-selective strategy based on the hard-soft acid-base theory,using MOF(Ti)as a structure-directing template.By incorporating Ce^(3+),Zn^(2+),In^(3+),and S^(2-),the MOF(Ti)is successfully converted into a hollow MOF(Ce)structure,while Ce-doped ZnIn_(2)S_(4)nanosheets nucleates on its surface.This process yields a highly active 2D/3D hollow core-shell heterojunction photocatalyst,Ce-ZnIn_(2)S_(4)/MOF(Ce).Both theoretical and experimental results demonstrate that this unique structure significantly enhances charge separation and extends the charge carrier's lifetime,leading to markedly improved photocatalytic hydrogen evolution performance.This work offers an innovative and controllable approach for synthesizing MOF-derived hollow core-shell heterojunctions,paving the way for a highly efficient water-splitting system.
基金supported by Shanxi Province Science Foundation for Youths(202203021212300)Taiyuan University of Science and Technology Scientific Research Initial Funding(20212064)Outstanding Doctoral Award Fund in Shanxi Province(20222060).
文摘The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these catalysts were buried in the carbon matrix,resulting in a low metal utilization and inaccessibility for adsorption of reactants during the catalytic process.Herein,we reported a facile synthesis based on the hard-soft acid-base(HSAB)theory to fabricate Co single-atom catalysts with highly exposed metal atoms ligated to the external pyridinic-N sites of a nitrogen-doped carbon support.Benefiting from the highly accessible Co active sites,the prepared Co−N−C SAC exhibited a superior oxygen reduction reactivity comparable to that of the commercial Pt/C catalyst,showing a high turnover frequency(TOF)of 0.93 e^(−)·s^(-1)·site^(-1)at 0.85 V vs.RHE,far exceeding those of some representative SACs with a ultra-high metal content.This work provides a rational strategy to design and prepare M−N−C single-atom catalysts featured with high site-accessibility and site-density.
