The development of nonprecious-metal-based electrocatalysts with high oxygen reduction reaction (ORR) activity, low cost, and good durability in both alkaline and acidic media is very important for application of full cells. Herein, we developed a facile and economical strategy to obtain porous core-shell Fe3C embedded nitrogen-doped carbon nanofibers (Fe3C@NCNF-X, where X denotes pyrolysis temperature) by electrospinning of polyvinylidene fluoride (PVDF) and FeCl3 mixture, chemical vapor phase polymerization of pyrrole, and followed by pyrolysis of composite nanofibers at high temperatures. Note that the FeCl3 and polypyrrole acts as precursor for Fe3C core and N-doped carbon shell, respectively. Moreover, PVDF not only plays a role as carbon resources, but also provides porous structures due to hydrogen fluoride exposure originated from thermal decomposition of PVDF. The resultant Fe3C@NCNF-X catalysts, particularly Fe3C@NCNF-900, showed efficient electrocatalytic performance for ORR in both alkaline and acidic solutions, which are attributed to the synergistic effect between Fe3C and N-doped carbon as catalytic active sites, and carbon shell protects Fe3C from leaching out. In addition, the Fe3C@NCNF-X catalyst displayed a better long-term stability, free from methanol crossover and CO-poisoning effects than those of Pt/C, which is of great significance for the design and development of advanced electrocatalysts based on nonprecious metals.

Poly( N-vinyl-2-pyrrolidone) (PVP)-coated Fe3O4 nanocrystals were prepared by a "one-pot" synthesis through the pyrolysis of ferric triacetylacetonate (Fe(acac)3) in N-vinyl-2-pyrrolidone (NVP). The polymerization of NVP was followed by measuring the shear viscosity of the reaction mixture. The PVP molecules formed in the reaction mixture was investigated by gel permeation chromatography. As the resultant Fe3O4 nanocrystals presented superdispersibility in 10 different types of organic solvents and aqueous solutions with different pH, including 0.01 M phosphate-buffered saline buffer, their hydrodynamic properties in both organic and aqueous systems were investigated by dynamic light-scattering. The results indicated that the PVP-coated Fe3O4 nanocrystals can completely be dispersed forming stable colloidal solutions in both organic solvents and water. Fourier transform infrared spectroscopy results suggested that PVP interacted with Fe3O4 via its carbonyl groups. Further surface analysis by X-ray photoelectron spectroscopy revealed that there were both coordinating and noncoordinating segments of PVP on the particle surface; the molar ratio between them was of 1:2.6.

A highly flexible all-solid-state symmetric supercapacitor using an aramid nanofibers/PEDOT:PSS (ANFs/PEDOT:PSS) film exhibits excellent energy density and cycling stability.

The electrochemical CO2 reduction reaction (CO2RR) to produce CO and H2 (syngas) is a promising method for clean energy, but challenges remain, such as controlling the CO/H2 ratios required for the syngas yield. Herein, hydrophobic exfoliated MoS2 (H‐E‐MoS2) nanosheets are fabricated from bulk MoS2 by a cost‐effective ball‐milling method, followed by decoration with fluorosilane (FAS). H‐E‐MoS2 is a cost‐effective electrocatalyst capable of directly reducing CO2 and H2O for tuneable syngas production with a wide range of CO/H2 ratios (from 1:2 to 4:1). In addition, H‐E‐MoS2 shows a high current density, 61 mA cm−2 at −1.1 V, and the highest CO FE of 81.2% at −0.9 V, which are higher than those of unmodified MoS2. According to density functional theory calculations, FAS decoration on the surface of MoS2 electrode can change the electronic properties of the edge Mo atom, which facilitates the rate‐limiting CO‐desorption step, thus promoting CO2RR. Moreover, the hydrophobic surface of H‐E‐MoS2 depressed the H2 evolution reaction and created abundant three‐phase contact points that provided sufficient CO2. The hydrophobization of the electrode may provide an effective strategy for easily tuning the CO/H2 ratio of syngas in a large range for the direct electroreduction CO2 to syngas with an optimized CO/H2 ratio.