In-situ self-templated preparation of porous core-shell Fe_(1-x)S@N,S co-doped carbon architecture for highly efficient oxygen reduction reaction

Transition metal compound(TMC)/carbon hybrids,as prospering electrocatalyst,have attracted great attention in the field of oxygen reduction reaction(ORR).Their morphology,structure and composition often play a crucial role in determining the ORR performance.In this work,we for the first time report the successful fabrication of porous core-shell Fe_(1-x)S@N,S co-doped carbon(Fe_(1-x)S@NSC-t,t represents etching time)by a novel in-situ self-template induced strategy using Fe3O4 nanospheres and pyrrole as sacrificial self-template.The post-polymerization of pyrrole can be accomplished by the Fe^(3+)released through the etching of Fe_(3)O_(4) by HCl acid.Thus,the etching time has a significant effect on the morphology,structure,composition a nd ORR performance of Fe_(1-x)S@NSC-t.Based on the cha racterizations,we find Fe_(1-x)S@NSC-24 can realize effective and balanced combination of Fe_(1-x)S and NSC,possessing porous core-shell architecture,optimized structure defect,specific surface area and doped heteroatoms configurations(especially for pyridinic N,graphitic N and Fe-N structure).These features thus lead to outstanding catalytic activity and cycling stability towards ORR.Our work provides a good guidance on the design of TMC/carbon-based electrodes with unique stable morphology and optimized structure and composition.

A facile self-catalyzed CVD method to synthesize Fe3C/N-doped carbon nanofibers as lithium storage anode with improved rate capability and cyclability

Uniform Fe3 C/N-doped carbon nanofibers were successfully synthesized through a facile self-catalyzed CVD method by using acetylene as carbon source and Fe3O4 as iron source and autocatalytic template for the reaction under moderate preparation conditions. The experimental and theoretical calculation results demonstrate that Fe3 C can improve the lithium storage performance of carbon nanofibers. Besides, the addition of PPy can not only control the growth rate of carbon fibers but also help to form uniform carbon fibers. As a result, the obtained Fe3 C/N-doped carbon nanofiber composites display favorable electrochemical performance as an anode for lithium-ion batteries, which including satisfactory rate performance of 402 m A h g-1 under 1.2 Ag-1, and good cycling stability of 502.3 m A h g-1 under 200 m Ag-1 over 400 cycles. The introduction of Fe3 C species and the uniform carbon fiber morphology are responsible for the long-cycling and high rate performance of materials.

Doped, conductive SiO_(2) nanoparticles for large microwave absorption

Although many materials have been studied for the purpose of microwave absorption,SiO_(2) has never been reported as a good candidate.In this study,we present for the first time that doped,microwave conductive SiO_(2) nanoparticles can possess an excellent microwave absorbing performance.A large microwave reflection loss(RL)of−55.09 dB can be obtained.The large microwave absorption originates mainly from electrical relaxation rather than the magnetic relaxation of the incoming microwave field.The electrical relaxation is attributed to a large electrical conductivity that is enabled by the incorporation of heterogeneous(N,C and Cl)atoms.The removal of the magnetic susceptibility only results in a negligible influence of the microwave absorption.In contrast,the removal of the heterogeneous atoms leads to a large decrease in the electrical conductivity and microwave absorption performance.Meanwhile,the microwave absorption characteristics can be largely adjusted with a change of the thickness,which provides large flexibility for various microwave absorption applications.