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

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.

Role of precursors on the photophysical properties of carbon nitride and its application for antibiotic degradation.

In this paper, we provide a comprehensive evaluation of graphitic carbon nitride (C3N4) powders derived from the four different precursors melamine, cyanamide, thiourea, and urea for the photocatalytic degradation of tetracycline (TC) antibiotic under sunlight irradiation. The powders were synthesized by employing the conventional thermal decomposition method. The synthesized powders were examined using different characterization tools for evaluating the photophysical properties. The degradation profile revealed that urea-derived C3N4 showed the highest activity while melamine-derived C3N4 showed the least activity. The TC degradation efficiency of the photocatalyst was found to be influenced more by the surface area values despite extended absorption by melamine in the visible light region. Stability tests on urea-derived C3N4 and others were checked by four runs of TC degradation under sunlight irradiation. The synthesized C3N4 powders also confirmed the dominance of urea-derived powders for cyclic stability.

Graphene Oxide Sheathed ZIF-8 Microcrystals: Engineered Precursors of Nitrogen-Doped Porous Carbon for Efficient Oxygen Reduction Reaction (ORR) Electrocatalysis.

Nitrogen containing mesoporous carbon obtained by the pyrolysis of graphene oxide (GO) wrapped ZIF-8 (Zeolitic Imidazolate Frameworks-8) micro crystals is demonstrated to be an efficient catalyst for the oxygen reduction reaction (ORR). ZIF-8 synthesis in the presence of GO sheets helped to realize layers of graphene oxide over ZIF-8 microcrystals and the sphere-like structures thus obtained, on heat treatment, transformed to highly porous carbon with a nitrogen content of about 6.12% and surface area of 502 m2/g. These catalysts with a typical micromeso porous architecture exhibited an onset potential of 0.88Vvs RHE in a four electron pathway and also demonstrated superior durability in alkaline medium compared to that of the commercial Pt/C catalyst. The N-doped porous carbon derived from GO sheathed ZIF-8 core-shell structures could therefore be employed as an efficient electrocatalyst for fuel cell applications.