Multifunctional Hollow Porous FeO@N-C Nanocomposites as Anodes of Lithium-Ion Battery, Adsorbents and Surface-Enhanced Raman Scattering Substrates.

At present, it is still a challenge to prepare multifunctional composite nanomaterials with simple composition and favorable structure. Here, multifunctional FeO@nitrogen-doped carbon (N-C) nanocomposites with hollow porous core-shell structure and significant electrochemical, adsorption and sensing performances were successfully synthesized through the hydrothermal method, polymer coating, then thermal annealing process in nitrogen (N) and lastly etching in hydrochloric acid (HCl). The morphologies and properties of the as-obtained FeO@N-C nanocomposites were markedly affected by the etching time of HCl. When the FeO@N-C nanocomposites after etching for 30 min (FeO@N-C-3) were applied as the anodes for lithium-ion batteries (LIBs), the invertible capacity could reach 1772 mA h g after 100 cycles at the current density of 0.2 A g, which is much better than that of FeO@N-C nanocomposites etched, respectively, for 15 min and 45 min (948 mA h g and 1127 mA h g). Additionally, the hollow porous FeO@N-C-3 nanocomposites also exhibited superior rate capacity (950 mA h g at 0.6 A g). The excellent electrochemical properties of FeO@N-C nanocomposites are attributed to their distinctive hollow porous core-shell structure and appropriate N-doped carbon coating, which could provide high-efficiency transmission channels for ions/electrons, improve the structural stability and accommodate the volume variation in the repeated Li insertion/extraction procedure. In addition, the FeO@N-C nanocomposites etched by HCl for different lengths of time, especially FeO@N-C-3 nanocomposites, also show good performance as adsorbents for the removal of the organic dye (methyl orange, MO) and surface-enhanced Raman scattering (SERS) substrates for the determination of a pesticide (thiram). This work provides reference for the design and preparation of multifunctional materials with peculiar pore structure and uncomplicated composition.