Amino Acid Mediated Highly Ordered Carbon Dots as Phase Directing Agent for Synthesizing α-Ni(OH)<sub>2</sub>Decorated with Nitrogen Doped CD as an Electrode for an Efficient Symmetric Supercapacitor
Atika, Raj Kumar Dutta
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.