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

Abstract

Herein, a method for synthesizing highly porous single phase of α‐Ni(OH)2 via hydrothermal route is presented. Nitrogen‐ and phosphorous‐functionalized carbon dots (N,P‐CDGMP) are first synthesized by thermal refluxing of 1,5′‐guanosine monophosphate (GMP) in ethylene glycol. Then Ni(OH)2 is synthesized in the presence of N,P‐CDGMP by hydrothermal method. Microflower‐like morphology of porous nanocomposite of Ni(OH)2‐[N,P‐CDGMP] with significantly enhanced Brunauer–Emmett–Teller surface area (454 m2 g−1) is formed, which is 32 times higher than that of the pristine Ni(OH)2. The cyclic voltammetry plot suggests battery‐type supercapacitor with a specific capacity of 632 C g−1, which is 6 times higher than the pristine Ni(OH)2 (107 C g−1). The enhanced specific capacity of Ni(OH)2‐[N,P‐CDGMP] is attributable to better intercalation–deintercalation of electrolyte ions in the suitable pore volumes. Electrode kinetic studies measured at a scan rate of 0.005 V s−1 suggest that about 86% of charge is stored via diffusion‐controlled process and the charge storage by surface‐controlled capacitive process is higher at higher scan rate (e.g., at 0.1 V s−1). The application of Ni(OH)2‐[N,P‐CDGMP] is demonstrated by fabricating a hybrid supercapacitor device Ni(OH)2‐[N,P‐CDGMP]//porous activated carbon from eucalyptus wood. The retention of specific capacitance of the device is 75% after 3000 cycles with maximum energy density of 31 Wh kg−1 and power density of 0.76 kW kg−1.