1D
nanofibers with higher surface area, small pore size, high porosity,
good electrical conductivity, and relatively high production rate
with high fiber interconnectivity have gained attention as energy
materials. In the present study, citrate-stabilized 1D cobalt oxide
nanofibers are prepared by the electrospinning technique using polyvinylpyrrolidone
(PVP) polymer followed by annealing at 500 °C where PVP acts
as the carbon source leading to highly porous 1D Co3O4@C nanofibers exhibiting enhanced specific capacitance. Microscopic
and structural characterization illustrates that the rod-shaped Co3O4 is interlinked with each other through polymer-derived
carbon in the form of a nanofiber network. The electrospun Co3O4@C nanofibers demonstrate a specific capacitance
of 731.2 F g–1 at a current density of 8 A g–1 in the 0.1 M KOH electrolyte. Furthermore, the Co3O4@C nanofibers show better cyclic stability with
an excellent capacity retention of 100% after 3000 continuous GCD
cycles at a current density of 9 A g–1. Again, the
asymmetric supercapacitor system with the PVA–KOH electrolyte
was fabricated and showed a specific capacitance of 120. 8 F g–1 (12.08 mF cm–2) with an energy
density of 37.75 Wh kg–1 (3.77 mWh cm–2) and power density of 1800 W kg–1 (180 mW cm–2) at 0.6 A g–1 (0.06 mA cm–2) current density. The symmetric supercapacitor shows 100% retention
in specific capacitance after 4000 GCD cycles. The enhanced supercapacitor
performance of 1D Co3O4@C nanofibers was attributed
to their unique nanofibrous structure with greater active surface
area provided by the in situ carbon, facilitating a faster ion and
electron transfer.
For the first time, the process of Fermi level equilibration has been studied and compared for plasmonic metal nanoparticles (PMNPs) supported on conducting substrates i.e. graphene oxide (GO) sheets.
A simplistic and
facile approach for the fabrication of Nafion-free
highly efficient oxygen reduction
reaction (ORR) electro-catalyst based on Pt3Co alloy nanoparticles
supported on carbon fiber paper (Pt3Co@CFP) via potentiostatic
electro-deposition method is presented. Besides being rapid and facile,
this method is highly effective and allows easy control over the kinetics
of nucleation and growth process as a function of electro-deposition
parameters. Here, we have optimized the electro-deposition time to
obtain the Pt3Co electro-catalyst loaded CFP as a Nafion-free
electrode that shows enhanced electro-catalytic activity for ORR after
fabricating Pt3Co@CFP electrode via electro-deposition
of Pt3Co on CFP for varying time intervals, viz. 5, 10,
15, and 20 min. The ORR electro-catalytic activity of Pt3Co electro-deposited for varying time intervals has been noted to
be a function of varying physicochemical features such as predominance
of (111) diffraction plane, ratio of Pt-oxide to metallic Pt, and
the size and morphology of the electro-deposits, which in turn can
be controlled by varying the electro-deposition time. The Pt3Co@CFP electro-catalyst obtained at electro-deposition time of 10
min exhibited the best ORR activity among others, following four electron
transfer pathways with minute peroxide formation. Moreover, the corresponding
electro-catalysis parameters for ORR, viz. onset potential of 0.85
V vs RHE at 1.0 mA cm–2 of current density, limiting
current density of 25.8 mA cm–2 at 2500 rpm and
0.2 V vs RHE, Tafel slope of 63 mV dec–1, intrinsic
current density of 40.44 mA cm–2, and 4.18 ×
10–3 cm s–1 are best compared
to the previously reported values for Pt3Co alloy based
electro-catalysts. Furthermore, we also studied the effect of Nafion
binder on the electro-catalytic activity toward ORR which suggests
that the Nafion binder lowers the ORR activity of the Pt3Co catalyst as indicated by lower specific current density and shifting
the peak potential to the higher potential.
Development of an efficient non-precious metal-based bi-functional oxygen electro-catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for various electrochemical energy conversion and storage devices. Prussian...
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