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

Abstract

Morphologically engineered porous electrodes show great promise in energy applications as they exhibit improved electrochemical activity owing to increased electrical conductivity, increased surface area, and a shorter path length for ion transport. Herein, the role of precursors (chlorides, acetates and nitrates) on the crystallinity and textural features of Nickel Cobaltite, obtained by the controlled precipitation through hydrothermal synthesis, is studied. The synthesis yielded urchin like structures with morphological variations in substructures based on the precursor anion types. The surface area values obtained for nickel cobaltite derived from the chloride (NCO-C), nitrate (NCO-N), and acetate precursors (NCO-A) were 30,110 and 115 m2 g−1, confirming the influence of anions on the textural features. The time dependant electrolyte (2 M KOH) infiltration behaviour on the electrode surfaces based on contact angle measurements is invoked to correlate its morphological and textural attributes with the electrolyte transport kinetics. The electrochemical performances were derived from cyclic voltammetry, galvanostatic charge discharge analysis and impedance measurements. The electrolyte infiltration studies established a dependence on the precursor anion. NCO-A facilitated faster electrolyte infiltration time of 7800 ms compared to 16200 ms and 54,000 ms for NCO-N and NCO-C electrodes, respectively. Furthermore, NCO-A exhibited a greater specific capacitance of 802 F g−1 than NCO-N (500 F g−1) and NCO-C (342 F g−1). The morphology modulation coupled with optimal porosity led to conducive pathways for reversible electrolyte infiltration resulting in increased capacitive contribution in NCO-A. The study revealed that the size of intercalating anions exercised a significant impact on the morphological and electrochemical features, signifying the importance of synthetic approaches in determining the functional properties of electrode materials.