Nickel Foam-Supported NiCo₂O₄ Urchin-Shaped Microparticles Sheathed with NiCoO₂ Nanosheets as Electrolyte-Wettable Electrodes for Supercapacitors

Abstract

Self-supported NiCo 2 O 4 −NiCoO 2 sheathed architectures on nickel foam (NCO-nco/NF), obtained by a two-step hydrothermal, postcalcination treatment, are demonstrated to be an efficient battery-type electrode for supercapacitors. NiCoO 2 nanosheets uniformly extend over the NiCo 2 O 4 urchin resulting in a synergistic association wherein the intrinsic redox ability of the scaffold and the sheath's superior hydroxyl adsorption capacity enabled enhanced electrochemical performance compared to a reverse architecture (nco-NCO/NF). Moreover, the NCO-nco/NF composite electrode with a favorable meso−macro porosity gave a high specific charge of 1373 C g −1 (1961 F g −1 ) with appreciable endurance in KOH electrolyte (5000 cycles). Additionally, an NCO-nco/NF and activated carbon hybrid supercapacitor assembly demonstrated a high energy density of 66.6 W h kg −1 at a power density of 400 W kg −1 . The unique electrode design combining the individual attributes of the constituent units offers the possibility of developing high-performing electrode materials for supercapacitor applications.

Modulating the Morphological Features of Hydrothermally Derived Nickel Cobaltite for Supercapacitor Application: Role of Precursor Anions

“…The obtained b values for NCO‐A, NCO‐N and NCO‐C electrodes at intermediate scan rates are 0.79, 0.74, and 0.60 (Figure 11(a)), respectively confirming capacitive and diffusion contributions in tandem, a phenomenon characteristic of porous and morphologically tuned extrinsic pseudocapacitors [42] . Figure 11 (b) compares the diffusion and capacitive contributions at different scan rates towards the CV current response for the three NCO samples elucidated as previously reported [43] . The capacitance contribution of the NCO‐A electrode was 60 %, which was more significant compared to 45 % for NCO‐N and 21 % for NCO‐C.…”

“…[10] The formed precursor can be converted into the respective metal oxides by slow calcination helping the morphology of the products to be preserved. The formation of the NiÀ Co precursor is elucidated by Equations (3-6) [11] COðNH…”

“…The formed precursor can be converted into the respective metal oxides by slow calcination helping the morphology of the products to be preserved. The formation of the Ni−Co precursor is elucidated by Equations (3– [11] $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr {\rm CO}({\rm NH}{_{2}}){_{2}}+{\rm H}{_{2}}{\rm O}\rightarrow {\rm 2NH}{_{3}}+{\rm CO}{_{2}}\hfill\cr}}$$$ $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr {\rm CO}{_{2}}+{\rm H}{_{2}}{\rm O}\rightarrow {\rm CO}{_{3}}{^{2- }}+{\rm 2H}{^{+}}\hfill\cr}}$$$ $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr {\rm NH}{_{3}}+{\rm H}{_{2}}{\rm O}\rightarrow {\rm NH}{_{4}}{^{+}}+{\rm OH}{^{- }}\hfill\cr}}$$$ $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr 2/{\rm 3Ni}{^{2+}}+4/{\rm 3Co}{^{2+}}+{\rm CO}{_{3}}{^{2- }}+{\rm 2OH}\hbox{-}\rightarrow {\rm Ni}{_{2/3}}{\rm Co}{_{4/3}}({\rm OH}){_{2}}{\rm CO}{_{3}}\hfill\cr}}$$$ …”

“…[42] Figure 11 (b) compares the diffusion and capacitive contributions at different scan rates towards the CV current response for the three NCO samples elucidated as previously reported. [43] The capacitance contribution of the NCO-A electrode was 60 %, which was more significant compared to 45 % for NCO-N and 21 % for NCO-C. The NCO-A sample with its porous petal-like substructures allows for enhanced active site exposure leading to reversible electrolyte permeation.…”

“…Materials characterization : XRD, FTIR, FESEM, TEM, XPS and BET surface area measurements are carried out as detailed in our recent publication [43] Electrolyte infiltration on the electrode surfaces was measured using KRUSS (DSA30E, Germany) water contact angle goniometer.…”