Strongly coupled N-doped carbon/Fe3O4/N-doped carbon hierarchical micro/nanostructures for enhanced lithium storage performance

A strong interface coupling is of vital importance to develop metal oxide/carbon nanocomposite anodes for next-generation lithium ion batteries.Herein,a rational N-doped carb on riveting strategy is designed to boost the lithium storage performance of Fe3O4/N-doped carbon tubular structures.Poly pyrrole(PPy)has been used as the precursor for N-doped carbon.N-doped carbon-riveted Fe3O4/N-doped carbon(N-C@Fe3O4@N-C)nanocomposites were obtained by pyrolysis of PPy-coated FeOOH@PPy nanotubes in Ar atmosphere.When tested as an anode for LIBs,the N-C@Fe3O4@N-C displays a high reversible discharge capacity of 675.8 mA h g-1 after 100 cycles at a current density of 100 mA g-1 and very good rate capability(470 mA h g_1 at 2 A g-1),which significantly surpasses the performance of Fe3O4@N-C.TEM analysis reveals that after battery cycling the FeOx particles detached from the carbon fibers for Fe3O4@N-C,while for N-C@Fe3O4@N-C the FeOx particles were still trapped in the carbon matrix,thus preserving good electrical contact.Consequently,the superior performance of N-C@Fe3C)4@N-C is attributed to the synergistic effect between Fe3O4 and N-doped carbon combined with the unique structure properties of the nanocomposites.The strategy reported in this work is expected to be applicable for designing other electrode materials for LIBs.

Hierarchical NiCo2O4 microspheres assembled by nanorods with p-type response for detection of triethylamine

The morphological and structural design provides an efficient protocol to optimize the performance of gas sensing materials.In this work,a gas sensor with high sensitivity for triethylamine(TEA)detection is developed based on p-type NiCo2 O4 hierarchical microspheres.The NiCo2 O4 microspheres,synthesized by a hydrothermal route,have a three-dimensional(3 D)urchin-like structure assembled by nanorod building blocks.The structure-property correlation has been investigated by powder X-ray diffraction,X-ray photoelectron spectroscopy,transmission electron microscope,scanning electron microscope,N2 adsorption-desorption tests and comprehensive gas sensing experiments.The influence of calcination temperature on the morphological structure and sensing performances has been investigated.Results reveal that the material annealed at 300℃has a very large specific surface area of 125.27 m2/g,thereby demonstrating the best TEA sensing properties including high response and low limit of detection(145 ppb),good selectivity and stability.The further increase of the calcination temperature leads to the collapse of the 3 D hierarchical structure with significantly decreased surface area,which is found to decline the sensing performances.This work indicates the promise of ternary p-type metal oxide nanostructures for application in highly sensitive gas sensors.