Amino Acid Mediated Highly Ordered Carbon Dots as Phase Directing Agent for Synthesizing α-Ni(OH)₂Decorated with Nitrogen Doped CD as an Electrode for an Efficient Symmetric Supercapacitor

Abstract

The synthesis of the α-phase of layered Ni(OH)2 is desirable owing to its efficient charge storage applications. The hydrothermal route of synthesis usually leads to formation of mixed of α- and β-phases of Ni(OH)2. We present here a novel hydrothermal approach for synthesizing predominantly the α-phase of Ni(OH)2 using a nitrogen doped crystalline carbon dot ([N-CD]BA) as a phase directing agent. The reaction medium comprising [N-CD]BA led to the formation of a microflower-like structure denoted as Ni(OH)2/[N-CD]BA with more petal density than in pristine α/β mixed phases of Ni(OH)2. The structure, composition, texture, and morphology of the as-synthesized batches of Ni(OH)2/[N-CD]BA and pristine Ni(OH)2 are thoroughly characterized. The electrochemical studies recorded by cyclic voltammetry and galvanostatic charging–discharging measurements demonstrated a battery-type supercapacitor. The batch of Ni(OH)2 prepared with 12.5 vol % [N-CD]BA, denoted as Ni(OH)2/12.5%[N-CD]BA, exhibited an optimum specific capacity of 482 C g–1 recorded at 1.0 A g–1, which is 4.5 times higher than that of pristine Ni(OH)2. The enhanced charge storage and transport mechanism are explained from electrochemical impedance spectroscopy (EIS). The high power density is reflected from a small relaxation time (0.4 s), and the charging–discharging efficiency is also improved for α-Ni(OH)2/12.5%[N-CD]BA. The application of the materials as supercapacitors has been demonstrated by fabricating a symmetric supercapacitor (SSC) device, i.e., Ni(OH)2/[N-CD]BA//Ni(OH)2/[N-CD]BA, using 2 M KOH as the electrolyte. The SSC exhibited a maximum energy density of 24 Wh kg–1 and a power density of 1.5 kW kg–1. The real-time application of the symmetric supercapacitor device has been demonstrated by successfully illuminating red LED lamps and powering a motor driven 1.6 mW fan.

In Situ Synthesis of Exfoliated Ni(OH)2 Nanosheets and AgNPs-Embedded Functionalized Polyindole-Based Trinary Hybrid Microspheres: A Z-Scheme Photocatalyst for the Sunlight-Driven Degradation of Organic Pollutants with Enhanced Antibacterial Efficacy

“…In addition, two more satellite peaks are observed at 861.1 and 879.3 eV . In contrast, both the deconvoluted Ni 2p high-resolution spectra of binary NH/PIn/MAA and ternary NH/PIn/MAA/Ag heterostructures show a positive shifting in the binding energy of about 0.6–0.8 eV (Figure a), suggesting prominent interactions between NH moieties with the other constituents via reduction of outer electron cloud density. − In the deconvoluted O 1s XPS spectrum of Ni(OH) 2 microflowers, three well-defined peaks at 529.0, 529.9, and 531.2 eV are, respectively, attributed to lattice oxygen (M–O–M, where M = Ni), surface hydroxyl group, and adsorbed water (Figure b). ,, For both NH/PIn/MAA and NH/PIn/MAA/Ag, the O 1s spectrum can be deconvoluted to four distinct XPS peaks, where one peak is associated with the lattice oxygen (M–O–M, where M = Ni), one is for the surface hydroxyl group, and the remaining two are designated for the carboxyl oxygens of the MAA moieties (Figure b) . The peaks for NH/PIn/MAA at 284.3, 285.6, and 286.8 eV and for NH/PIn/MAA/Ag at 284.5, 285.9, and 286.8 eV in the deconvoluted XPS spectra of C 1s (Figure S6a) correspond to CC, C–N/C–S, and O–CO bonds, respectively, suggesting the existence of polymer moieties in both the microspheres.…”

“…The survey spectra of pristine Ni(OH) 2 microflowers, NH/PIn/MAA, and NH/PIn/MAA/Ag confirm the existence of their representative elements, such as C, O, Ni, S, N, and Ag (Figure S5). In the Ni 2p high-resolution spectrum of pristine Ni(OH) 2 microflowers (Figure a), two spin–orbit doublet peaks are ascribed at binding energies of 855.1 and 873.1 eV, which correspond to the Ni 2p 3/2 and Ni 2p 1/2 states of Ni 2+ , respectively . In addition, two more satellite peaks are observed at 861.1 and 879.3 eV .…”

Nucleotide‐Based Carbon Dot‐Assisted Synthesis of High Surface Area Porous α‐Ni(OH)2 as an Efficient Battery‐Type Supercapacitor Electrode

“…Synthesis of Ni(OH) 2 Decorated with N,P-CDGMP: Our group has developed a simple hydrothermal method of synthesizing nanocomposites of Ni(OH) 2 and amino acid conjugated ethylene glycol-based CDs. [16] Here, we present a similar strategy using nucleotide conjugated with ethylene glycol to synthesize nitrogen and phosphorous-functionalized CDs. For the synthesis of Ni(OH) 2 -[ N,P-CD GMP ] composite, 1 mmol Synthesis of Biomass-Derived Porous-Activated Carbon: The oxygen-rich Eucalyptus wood-derived porous activated carbon has been synthesized by using KOH activation process in which Eucalyptus wood biomass is activated with KOH (1:3 weight ratio) in N 2 environment at 600 °C.…”

“…[13][14][15] In view of this, nanocomposites of Ni(OH) 2 with nitrogen-and oxygendoped carbon dots (CDs) showed the improved electrochemical property. [16][17][18] Compared to activated carbon, graphene or carbon nanotubes, the utilization of heteroatom doped CDs in synthesizing nanocomposites with Ni(OH) 2 as electrode material is preferable owing to its facile method of synthesis, easy availability of precursors, ability to conjugate with inorganic materials including Ni(OH) 2 and their nontoxicity. [19,20] The charge transportation in such composites with heteroatom-doped CDs might improve owing to the delocalization of electrons in the polarized electron density in the carbon framework.…”

Probing the Synergy of Ni(OH)2/NiO Nanoparticles Supported on rGO for Battery‐Type Supercapacitors

“…During the analysis, Whatman filter paper is utilized as a separator between the electrodes. The CV measurements revealed that the appropriate operating potential window is up to 0-1.4 V for both the materials, [52] and a sudden rise in the current is observed at high voltage because the battery-type materials involve the Faradaic reaction in which many kinetic effects lead to electrode polarization in battery materials, as shown in Figure 10a,c. However, the CV analysis for devices was studied from 10 to 80 mV s À1 , as shown in Figure 10b,d.…”