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A novel 3D interconnected web-like carbon material with high electrocatalytic activities toward oxygen reduction reaction (ORR) has been developed for the first time via direct carbonization of a composite (Zn-MOF-74@CNFs) comprising Zn-MOF-74s grown on carbon nanofibers (CNFs) web. The hexagonal pillar shaped Zn-MOF-74s with a diameter which ranges from 300 to 600 nm grow along the CNFs web by solvothermal method. After carbonization of Zn-MOF-74@CNFs, effective interconnections promoting electron transfer are successfully formed between carbonized Zn-MOF-74 (C-Zn-MOF-74) and on CNFs as well as C-Zn-MOF-74 themselves. The extraordinary 3D structure thus fabricated significantly improves the electrocatalytic activity toward ORR. The calculated electron transfers number (n) values for carbonized Zn-MOF-74@CNFs (C-Zn-MOF-74@CNFs) are nearly 4 at potentials ranging from 0.4 to 0.6 V (vs. reversible hydrogen electrode), demonstrating that the ORR process occurs dominantly through a direct four-electron pathway. Tafel slope of C-Zn-MOF-74@CNFs at low over-potential are lower than those from C-Zn-MOF-74 and even commercial Pt/C. Durability is also found to exceed that of commercial Pt/C. This study provides a novel 3D interconnected carbon material as a non-metal ORR electrocatalyst and design strategy for a large-area, self-standing and binder-free carbon-based electrochemical electrode.

Many efforts are continuously devoted to developing high-efficiency, low-cost, and highly scalable oxygen reduction reaction (ORR) electrocatalysts to replace precious metal catalysts. Herein, we successfully synthesize Co- and defect-rich carbon nanofibers (CNFs) using an efficient heat treatment approach involving the pyrolysis of electrospun fibers at 370 °C under air. The heat treatment process produces Co-decorated CNFs with a high Co mass ratio, enriched pyridinic N, Co-pyridinic Nx clusters, and defect-rich carbon structures. The synergistic effects from composition and structural changes in the designed material increase the number of catalytically active sites for the ORR in an alkaline solution. The prepared Co- and defect-rich CNFs exhibit excellent ORR activities with a high ORR onset potential (0.954 V vs. RHE), a large reduction current density (4.426 mA cm−2 at 0.40 V), and a nearly four-electron pathway. The catalyst also exhibits a better long-term durability than commercial Pt/C catalysts. This study provides a novel hybrid material as an efficient ORR catalyst and important insight into the design strategy for CNF-based hybrid materials as electrochemical electrodes.

Herein, we describe a microwave-assisted hydrothermal process to synthesize α-Fe2O3 nanotubes/SnO2 nanorods/reduced graphene oxide (FNT/S/RGO) for application as a high-performance anode in lithium-ion batteries (LIBs). The composite products exhibit anisotropic growth because of heteronucleation and the preferred orientation of SnO2. SnO2 nanorods on the FNT surfaces are converted into Sn metal during the alloying/dealloying reaction, which offers improved electrical conductivity. The FNT/S/RGO show substantially enhanced electrochemical properties because of the reduced volume expansion effect, which improves the electrical and Li-ion conductivity and provides a large surface area. As a consequence, the FNT/S/RGO anode delivers a high reversible capacity of 883 mA h g−1 even at a current density of 200 mA g−1, with a capacity retention of 90% between the 1st and 220th cycles, excellent high-rate capacity (382 mA h g−1 at 4320 mA g−1), and long-term cycle durability (maintaining 629 mA h g−1 at 1000 mA g−1 for 1000 cycles). The presented FNT/S/RGO electrodes are the most efficient SnO2- and Fe2O3-based anode electrodes reported thus far for LIBs. The origin of the synergistic effect and the reaction mechanism of the FNT/S/RGO was thoroughly investigated using various in situ transmission electron microscopy, electrochemical impedance spectroscopy, and X-ray diffraction analysis methods.

Compared to conventional electrode, a self-standing structure electrode is an effective way to achieve high performance of supercapacitor by maximizing the use of active material. We present a new combination of nickel oxide–carbon composites fabricated by directly carbonizing a nickel metal–organic framework (Ni-MOF)@carbon nanofiber (CNF) for a self-standing electrode of the supercapacitor application. The new scheme utilizes the CNF film as a substrate with high electron transferring capability and as a backbone of a self-standing electrode as well. It is observed that the MOF-derived NiOs with a diameter of ~ 8 nm are uniformly distributed in the carbon matrix and result in the improvement of the electrical conductivity. The self-standing electrode, NiO/C@CNF composite, provides a high rate capability with high specific capacitances of 742.2 and 671.1F g−1 (at 1 and 10 A g−1), respectively. An asymmetric supercapacitor (ASC) constructed from the NiO/C@CNF and the activated carbon exhibits an excellent specific energy density of 58.43 Wh kg−1 at a power density of 1,947 W kg−1. It is also confirmed that the ASC shows a good cycle stability from the long-term cycling test. It is demonstrated that the proposed nickel oxide–carbon composite has a potential as promising self-standing electrode materials for supercapacitors.

Metal-organic framework(MOF)-derived carbon material is a promising material for lithium-air battery cathode, but its pores are small (