Electrical Conduction in CoWO₄ Flanked by Carbon and ZnFe₂O₄ Nanoparticulate Assembly and a Poly(ethylene oxide) Gel for Enhanced Electrochemical Activity

Abstract

Semiconducting cobalt tungstate flanked by carbon (CoWO4@C) polyhedral microstructures with smooth facets and zinc ferrite (ZnFe2O4) polydisperse interconnected nanoparticles via intrinsic mechanisms of hole polaron transfer from Co3+ to Co2+ sites and electron hopping between Fe2+ and Fe3+ states, respectively, were endowed with high room-temperature electrical conductivities (>0.9 mS cm–1), thus enabling the fabrication of a high-performance asymmetric supercapacitor (ASC) possessing an outstanding rate capability as well as a good trade-off between power (P) and energy (E) densities. Furthermore, electrochemical response comparison of CoWO4@C//ZnFe2O4 ASCs encompassing three different electrolytes (aqueous KOH, KOH–PEO gel, and KOH–PVA gel) revealed that the KOH–PEO gel cell outperformed the other two ASCs, with a specific capacity (SC) of 339 F g–1 (at 1 A g–1) and E max and P max of 105 Wh kg–1 and 3.2 kW kg–1 achieved over an operational voltage window of 1.5 V while retaining 97% of the original SC after 10,000 cycles. With KOH and KOH–PVA gel, while the P max remained the same, SCs of 300 and 322 F g–1 and E max’s of 93 and 100 Wh kg–1 were obtained. The high ionic conductivity (81.6 mS cm–1) of the KOH-PEO gel is attributed to the hydrogen bonded networked structure of the gel with free spaces that allows ions to move freely within the polymer matrix. Further, the oxygens along the polymer chains ensure a high dissociation of KOH. The gel also serves as an ion-reservoir and these factors cumulatively resulted in the enhanced performance of the ASC. This study showcases that scalable, low-cost, leak-proof supercapacitors can be fabricated using environmentally friendly electroactive materials that can be synthesized easily using simple wet chemistry techniques.

Self-Sulfuration and Carbonization of a Mixed-Metal Aryl Sulfonium Polyoxometalate Hybrid: A Path to Electrocatalytically Active Ternary Composite

“…A proper doublet could not be deconvoluted in this case; the peak position could be explained as an average of the doublet, possibly because of its lower concentration in the material. Following the same line of discussion, the deconvoluted Co 2p scan of AS-CoPOM showed only a doublet at 781.2 and 797.4 eV owing to the 2p 3/2 and 2p 1/2 peaks of Co 2+ . Two satellite peaks of Co 2+ also appeared at ∼787 and ∼804 eV for all of the materials.…”

“…These peaks are attributed to the C�C of graphitic carbon, C−O from the C− OH bonds that might have arisen due to the oxidation of the graphitic carbon at high temperatures and the π−π* satellite peak, respectively. 47 Another interesting structural feature was also noticed in the case of AS-CoPOM700 and AS-CoPOM900. Here, along with the peaks discussed above, a new peak was observed at ∼285 eV, assigned to the nonconjugated carbon arising from the defects in the graphitic carbon.…”

“…Following the same line of discussion, the deconvoluted Co 2p scan of AS-CoPOM showed only a doublet at 781.2 and 797.4 eV owing to the 2p 3/2 and 2p 1/2 peaks of Co 2+ . 47 Two satellite peaks of Co 2+ also appeared at ∼787 and ∼804 eV for all of the materials. Moving on to the Co 2p scans of AS-CoPOM500− 900, all three samples showed mixed valent species of Co (+2 and +3).…”

Flexible Free-Standing Electrode of Nickel–Manganese Oxide with a Cracked-Bark Shape Composited with Aggregated Nanoparticles on Carbon Cloth for High-Performance Aqueous Asymmetric Supercapacitors

“…Long-term cycle stability is another critical parameter for practical electrodes. − Figure i) shows the cycling test for NMO at 30 mA cm –2 , and 80.2% of the initial capacitance can be reserved after 5000 cycles. Moreover, the approximately 100% Coulombic efficiency was maintained for these consecutive cycles, demonstrating good cycling stability/highly reversible Faraday reaction (see the cycling performance of NMO-1 and NMO-2 and comparison with NMO in Figure S6).…”

Recent progress in structural modification of polymer gel electrolytes for use in solid-state zinc-ion batteries

“…The main components of common hydrogel electrolytes are PVA, 67,85,86 polyacrylamide (PAM), [87][88][89] PEO, [90][91][92] polyvinyl chloride (PVC), 93,94 and xanthan gum (XG). [95][96][97] The above materials show excellent flexibility and good ionic conductivity as gel electrolytes.…”