Sagar C. Bhise

Low cost flexible 3-D aligned and cross-linked efficient ZnFe2O4 nano-flakes electrode on stainless steel mesh for asymmetric supercapacitors

A simple and economic approach for growth of 3-D aligned and cross-linked ZnFe2O4 nano-flakes on a flexible stainless steel mesh (FSSM) substrate (300 mesh) using a rotational chemical bath deposition technique for fabricating efficient asymmetric supercapacitors is reported. The prepared ZnFe2O4 nano-flake thin film (ZnFe2O4/FSSM-300) as an anode in combination with Ni(OH)2/FSSM-300 as a cathode was used as an asymmetric supercapacitor. Furthermore, ZnFe2O4 nano-flakes were also grown on FSSM with a different mesh and designated as ZnFe2O4/FSSM-200, ZnFe2O4/FSSM-250 and ZnFe2O4/FSSM-300 for investigating the effect of mesh size on the morphology formation and their electrochemical performance. Amongst the samples, ZnFe2O4/FSSM-300 exhibited excellent supercapacitive properties, such as a higher specific capacitance (1625 F g−1 at 1 mA cm−2) and excellent cycle stability (8000 cycles, 97% retention), which was marginally higher than ZnFe2O4/FSSM-250 (545 F g−1 at 1 mA cm−2, 70% retention), ZnFe2O4/FSSM-200 (241 F g−1 at 1 mA cm−2, 56% retention) and other earlier reported ferrites. In addition, the fabricated asymmetric pseudocapacitor device delivered better performance with high specific capacitance (118 F g−1 at 5 mA cm−2), excellent cycle stability (8000 cycles, 83% capacitance retention) and high energy density (42 W h kg−1) even at higher power density (5 kW kg−1).

Mechanochemical growth of a porous ZnFe2O4 nano-flake thin film as an electrode for supercapacitor application

Herein, we are reporting a simple, economic, easy to handle, scalable and reproducible mechanochemical i.e. rotational chemical bath deposition (R-CBD) approach for the synthesis of well adhered nano-flake ZnFe2O4 thin films (NFs-ZnFe2O4) with uniform morphology on a stainless steel (SS) substrate, in comparison with nano-grain ZnFe2O4 thin films (NGs-ZnFe2O4) prepared using a conventional CBD approach. The influence of rotation on the evolution of the nano-flake morphology in NFs-ZnFe2O4 is also investigated. The porous NFs-ZnFe2O4 thin films demonstrated excellent pseudocapacitor properties with higher specific capacitance of 768 F g−1 at high current density of 5 mA cm−2, stability upto 5000 cycles (88% retention), higher energy density (106 W h kg−1) and power density (18 kW kg−1) compared to NGs-ZnFe2O4. The results were also found to be higher than those reported earlier for MFe2O4 based systems.

Simple protic ionic liquid [Et3NH][HSO4] as a proficient catalyst for facile synthesis of biscoumarins

We have explored a number of protic ionic liquids (PILs) as a catalyst for the synthesis of biscoumarins by condensation of 4-hydroxycoumarin with an aromatic aldehyde. Methylimidazolium- and triethylammonium-based PILs were synthesized by simple neutralization reaction with protic acids. Triethylammonium hydrogen sulfate [Et3NH][HSO4] was found to be the best among the studied PILs concerning the yield of products and reaction time period. Different biscoumarin derivatives were synthesized based on 4-hydroxycoumarin and various substituted aromatic aldehydes at optimum reaction conditions. Obtained products were separated just by simple filtration. The facile method does not require additional purification for formed products. The catalyst has shown better yields along with outstanding recyclability, providing an environmental benign protocol for the synthesis of biscoumarin derivatives.Graphical AbstractScreening of simple protic ionic liquids as a catalyst in the synthesis of biscoumarins, out of which [Et3NH][HSO4] was found to be best among the studied PILs.