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[Display omitted] • The Ni-CAT/NiFe-LDH/CNFs catalyst demonstrated effective OER performance. • It has both a large surface area and significant intrinsic activity. • The catalyst was utilized to construct liquid-state and solid-state Zn-air batteries. • Optimizing the intermediate adsorption is the main factor in enhancing catalyst performance. NiFe layered double hydroxide (NiFe-LDH) is an efficient and widely available catalyst for the oxygen evolution reaction (OER), but further improvement of its OER property remains a challenge. Therefore, a conductive Ni-organic framework is triumphantly synthesized in-situ on NiFe-LDH/carbon nanofibers (Ni-CAT/NiFe-LDH/CNFs) through a hydrothermal treatment. This configuration utilizes the exposed surface area and the electron transfer pathways of Ni-CAT and CNFs, resulting in exceptional OER kinetics in alkaline conditions. A low overpotential of 370 mV at 10 mA cm−2 and a small Tafel slope of 79 mV dec−1 are achieved. The liquid-state Zn-air batteries, featuring Ni-CAT/NiFe-LDH/CNFs catalyst as an air cathode, indicate a significant peak power density of 292.1 mW cm−2 and an extended cycle durability of over 66 h. Solid-state Zn-air batteries demonstrate stable cycling at various flat/bent/flat states, showing great potential for flexible electronic device applications. According to experimental measurements and computational analysis, the in-situ growth of Ni-CAT on the NiFe-LDH matrix can optimize intermediate adsorption and alter hydrophilicity, resulting in improved performance of Zn-air batteries. [ABSTRACT FROM AUTHOR]

Rational design of highly effective and low-cost oxygen reduction reaction (ORR) electrocatalysts to replace Pt-based catalysts is still a significant challenge for rechargeable zinc-air batteries. Hence, Fe, N co-doped one-dimensional carbon nanofibers with Fe 4 N species (Fe/N-CNFs) are synthesized through the electrospun technique combining with the "rapid calcination under vacuum" method. Benefitting from the one-dimensional structure obtained by the electrospun technique, the as-synthesized Fe/N-CNFs electrocatalyst with mesoporous exhibits a relatively large specific surface area of 624.12 m2 g−1. Notably, the intrinsic activity of Fe 4 N species as well as the large specific surface area can endow the resulting Fe/N-CNFs with a positive half-wave potential of 0.88 V compared with 20 wt% Pt/C (0.86 V) for ORR. The Fe/N-CNFs also exhibits better long-term stability than 20 wt% Pt/C. Furthermore, the rechargeable zinc-air battery constructed with Fe/N-CNFs as the cathode shows a high open-circuit voltage of 1.51 V, a peak power density of 135 mW cm−2 and an excellent cycle life for 55 h. The as-synthesized electrocatalyst is promising to replace the precious metal catalysts for rechargeable zinc-air batteries. Unlabelled Image • Fe, N co-doped carbon nanofibers (Fe/N-CNFs) with Fe 4 N species were synthesized. • The "rapid calcination under vacuum" was reported for the preparation of Fe/N-CNFs. • The one-dimensional structure of Fe/N-CNFs provides a large specific surface area. • The Fe/N-CNFs exhibits more excellent ORR activity than commercial 20 wt% Pt/C. • The Fe/N-CNFs endows zinc-air batteries with comparable performances to 20 wt% Pt/C. [ABSTRACT FROM AUTHOR]

Recently, Li-ion capacitor as a kind of novel energy storage device with high energy density and power density have caused wide concern. In this study, the porous carbon nanofiber/molybdenum disulfide nanoflake-flowerballs composite material is successfully prepared via hydrothermal method using the three-dimensional porous carbon nanofibers as a carrier. The molybdenum disulfide nanoflake-flowerballs are uniformly distributed and fill in three-dimensional porous carbon nanofibers skeleton, and the clear composite material with nanofiber morphology is formed. This material presents moderate specific surface area (81.67 m2 g−1) and good electrical conductivity (22.32 S cm−1) and is used as the anode in the Li-ion capacitor, and the big energy density at high power density (the energy density could reach 75.5 Wh kg−1 and 22.5 Wh kg−1 at power densities of 0.075 kW kg−1 at 30 kW kg−1, respectively) are achieved, which has broad application prospect in the energy storage field. • The three-dimensional PCNF loading MoS 2 nanoflake-flowerballs was constructed. • The MoS 2 nanoflake-flowerballs inner nanofibers provide the large reaction area. • The three-dimensional PCNF skeleton offers conductive path. • The 3D-PCNF/MoS 2 -NFFBs used as the anodes of LICs exhibit excellent properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn-doped PAN nanofibers were decorated with ZIF-67. • Oriented attachment of PVP/ZIF-67 occurred on Mn-doped PAN-2MI nanofibers. • PVP/ZIF-67/Mn-fibers carbonized at 900 ℃ resulted in flexible C/Co-CoO x /Mn-CNF. • The areal capacitance of 1263 mF·cm−2 was obtained at a current density of 0.25 mA·cm−2. • The energy density of 0.18 mWh·cm−2 was obtained at a power density of 0.5 mW·cm−2. Electrodes for flexible supercapacitors were fabricated from manganese-doped carbon nanofibers (Mn-CNF) decorated with carbon-coated Co-CoO x (C/Co-CoO x) nanotubes. The Mn-doped polyacrylonitrile (PAN)–2-methylimidazole (2MI) solution was electrospun using optimized Mn concentrations and ZIF-67 was then surface loaded by wet impregnation with added polyvinylpyrrolidone (PVP). These ZIF-67 loaded Mn-fibers, when annealed, resulted in carbon-coated C/Co-CoO x nanotubes on the Mn-CNF surface. In the presence of PVP, ZIF-67 oriented attachment occurs, forming evenly dispersed CoO x particles even after high temperature annealing. XRD spectra exhibit the formation of metallic Co nanoparticles (NPs), whereas Raman spectra and XPS indicate Co particle oxidation. A carbon coating limits the oxidation of Co; thus, the particles are called C/Co-CoO x. A symmetric supercapacitor cell prepared using the CNFs decorated with C/Co-CoO x using an aqueous electrolyte has a capacitance of 1263 mF⋅cm−2 at a current density of 0.25 mA⋅cm−2 and a wide potential window of 1.4 V for the optimal case. Long-term cycling showed 110 % capacitance retention after 10,000 cycles. Moreover, bending tests and powering LEDs demonstrated the flexibility and improved charge storage of the prepared nanofiber electrodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A three-dimensional hierarchical catalyst (Co/CoFe NAs@NCNFs) was fabricated. • Co/CoFe NAs@NCNFs exhibited excellent catalytic activity for ORR, OER and HER. • The catalyst was used as a cathode catalyst for MFC and to drive water splitting. • The peak power density of the MFC can reach 2139.6 ± 43 mW m−2. Herein, a novel MOF-derived trifunctional electrocatalyst with a three-dimensional hierarchical structure of N -doped carbon nanofibers (NCNFs) compounded with vertically grown nanosheets loaded with Co and CoFe alloy nanoparticles is reported. It is found that Co/CoFe NAs@NCNFs has a good half-wave potential of 0.83 V for ORR, the overpotential of 290 mV and 103 mV for OER and HER, respectively. When Co/CoFe NAs@NCNFs catalyst is employed on the cathode of a microbial fuel cell (MFC), the peak power density of the MFC can reach 2139.6 ± 43 mW m−2, which is 1.56 times better than that of commercial Pt/C. Furthermore, the assembled MFCs can also successfully drive the water splitting. The above excellent performance is mainly due to the structure of the interwoven NCNF networks combined with nanosheets which greatly enhances the surface area and mass transfer capacity of the material, and the loaded nanoparticles are constructed into a large number of Fe-N x -C and Co-N x -C active sites, further increasing the catalytic performance of Co/CoFe NAs@NCNFs. This work could provide a novel approach to the regeneration and conversion of clean energy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tailoring interfacial property of anode using hollow CoFe 2 O 4 nanofibers. • Superior bacterial habitation capability due to the porous scaffold of CoFe 2 O 4 /CNTs. • Enhanced EET due to the multiple valences of Co and Fe ions. • Delivered 4.6 folds higher power output using CoFe 2 O 4 /CNTs electrocatalysts. • MFC with CoFe 2 O 4 /CNTs anode for successfully powering electronic devices. Currently, the commercial applications of MFCs are mainly constricted by the relatively lower power density derived from poor electroactive bacteria (EAB) adhesion and sluggish extracellular electron transfer (EET) at the anode interface. To address this issue, herein, hollow cobalt ferrite nanofibers integrating with carbon nanotubes (CoFe 2 O 4 /CNTs) are fabricated as an efficient anode electrocatalyst via simple electrospinning, pyrolysis, and in-situ hybrid process. Interestingly, the CoFe 2 O 4 /CNTs electrocatalysts with a continuously interconnected network not only strengthen the interfacial affinity with EAB but also promote the electron transfer efficiency between the anode and EAB, which endows the MFCs with a maximum power density of 2290 mW m−2, far exceeding the referential CoFe 2 O 4 (1458 mW m−2) and carbon cloth (496.7 mW m−2) anode. The outstanding power density can be attributed to the continuous porous scaffold, remarkable electrocatalytic activity toward the redox reactions in the biofilm, and positively charged cations with multiple valence states on the CoFe 2 O 4 /CNTs electrocatalyst, favoring the negatively charged Geobacter adhesion, colonization, and mediating long-distance EET across the thick biofilm. This research provides a new strategy for fabricating anode electrocatalysts to improve the overall MFCs performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient and stable bi-functional electrocatalyst is developed by a facile foaming-assisted electrospinning method. • FeCo alloy nanoparticles are uniformly embedded within N-doped mesoporous carbon nanofibers. • The FeCo@NCNF electrocatalyst exhibited excellent ORR and OER performances with a smaller potential gap (ΔE) of 0.749 V. • The as-constructed Zn-air battery exhibits a larger power density of 134.83 mW cm−2 and long-term cycling stability after 216 h tests. A low-cost, efficient and durable bi-functional electrocatalysts for bi-functional oxygen reduction/evolution reactions (ORR/OER) is vital for modern energy conversion devices. Here, we report the exploration of advanced OER/ORR bi-functional catalysts based on foaming-assisted electrospinning. The addition of foaming agent is beneficial to prevent the agglomeration of FeCo alloy nanoparticles decorated on the N-doped mesoporous carbon nanofibers (FeCo@NCNF). These rationally designed electrocatalysts exhibit an excellent bi-functional electrocatalytic activity with a low reversible overvoltage of 0.749 V. The as-constructed Zn-air battery delivers a power density of 134.83 mW cm−2 and long-term cycling stability with a slight increase of 0.02 V in potential gap over 216 h at 5 mA cm−2, surpassing to most bi-functional electrocatalysts ever reported. [ABSTRACT FROM AUTHOR]

• NPCNFs/PANI with Integrated architecture has been well designed. • 3D continuous and conductive network can reduce internal resistance effectively. • Large surface areas and hierarchical porosity decrease the ion diffusion length. • The all-solid-state flexible device exhibits desirable electrochemical properties. Electrode materials with rationally designed architecture are crucial to achieve high-performance supercapacitors. However, there is still a great challenge for integrating the features of large accessible surface areas, fast electron/ion transport kinetics and favorable mechanical flexibility within a single electrode. Herein, we propose a facile approach to fabricate high-performance freestanding carbon-based electrode of polyaniline modified nitrogen-doped hierarchical porous carbon nanofibers, which effectively combine the merits of highly conductive electrospun carbon nanofibers with hierarchical porous structure, suitable nitrogen content as well as pseudocapacitive materials. Benefiting from the well-designed architecture, the as-assembled symmetric all-solid-state flexible device exhibits a high specific capacitance of 260 F g−1 at 0.5 A g−1 and high rate capability with a capacitance retention of 60% at 16 A g−1. Furthermore, the device also displays a desirable energy density of 8.9 Wh kg−1 with power density of 0.27 kW kg−1 and excellent cycling stability with 80.1% capacitance retention after 10,000 charge-discharge cycles at 2 A g−1. Eventually, the as-designed composite electrodes open up new avenues for facile construction of high-performance supercapacitor electrodes. [ABSTRACT FROM AUTHOR]