Design of ZIF-67 nanoflake derived NiCo-LDH/rGO hybrid nanostructures for aqueous symmetric supercapattery application under alkaline condition

Abstract

Abstract Well-defined polyhedral ZIF-67 metal-organic frameworks (MOFs) are usually synthesized using methanol as solvent. In this work, methanol is replaced with deionized water as a solvent to synthesize ZIF-67 MOFs with unique nanoflake morphology. The ZIF-67 nanoflakes are synthesized directly by in situ method on reduced graphene oxide (rGO) to obtain ZIF-67/rGO- x precursors which are further transformed into NiCo-layered double hydroxide nanocomposites (NiCo-LDH/rGO- x , x = 10, 30, 50 and 90 mg of rGO). The NiCo-LDH/rGO- x nanostructured composites are found to be excellent materials for battery type supercapacitor (supercapattery) applications. Among these samples, the NiCo-LDH/rGO-30 composite gives maximum specific capacity of 829 C g −1 (1658 F g −1 ) at a current density of 1 A g −1 and high rate capability. The as fabricated 2-electrode symmetric Swagelok device <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close=")" open="(" separators=""> <mml:mrow> <mml:mi mathvariant="normal">NiCo</mml:mi> <mml:mo>‐</mml:mo> <mml:mi mathvariant="normal">LDH</mml:mi> <mml:mo>/</mml:mo> <mml:mi mathvariant="normal">rGO</mml:mi> <mml:mo>‐</mml:mo> <mml:mn mathvariant="normal">30</mml:mn> <mml:mrow> <mml:mfenced close="" open="∥" separators=""> <mml:mrow> <mml:mi mathvariant="normal">NiCo</mml:mi> <mml:mo>‐</mml:mo> <mml:mi mathvariant="normal">LDH</mml:mi> <mml:mo>/</mml:mo> <mml:mi>rGO</mml:mi> <mml:mo>‐</mml:mo> <mml:mi>3</mml:mi> <mml:mn>0</mml:mn> </mml:mrow> </mml:mfenced> </mml:mrow> </mml:mrow> </mml:mfenced> </mml:math> delivered a high energy density of 49.2 Wh kg −1 and a power density of 4511 W kg −1 , and enabled us to glow red, blue and white LED bulbs using three coin cells. The device can show good capacity retention even after 3000 continuous charge–discharge cycles. The NiCo-LDH/rGO-30 composite, in situ derived from ZIF-67 MOF in combination with optimal amount of rGO, is an excellent material to deliver both high energy density and high power density in supercapattery devices.

Topics & Concepts