Synthesis of Mn Based ZIF-67 Derived High Surface Area Carbon Electrodes for Supercapacitors /

Abstract

Zeolite imidazolate frameworks (ZIFs) derived high surface area materials have been established as the promising electrode materials in supercapacitors due to their tunable morphology, profuse N species and abundance heteroatom based electroactive sites. In this work, manganese-doped ZIF-67 derived nitrogen-doped carbon-based sulfide Mn/Co/NC/S electrode is synthesized for augmented performance in supercapacitors. The manganese doped ZIF-67 (MnCo-ZIF) is synthesized by the simple co-precipitation method. MnCo-ZIF is converted to nitrogen doped porous carbon structure (Mn/Co/NC) through heat treatment in controlled environment (Ar/H2 90:10) at a very slow heating rate of 3 ºC/min. Subsequently, the ion exchange sulfidation reaction is conducted in hydrothermal autoclave at 180 ºC for 12 hours to convert Mn/Co/NC to Mn/Co/NC/S. MnCo-ZIF(ZIF_8/1) exhibits 2D leaf-like morphology with dimension of 5.51 × 2.61 µm. Mn/Co/NC(C_8/1) material shows a highly porous carbon structure. The synthesized Mn/Co/NC/S (CS_8/1) material exhibits porous 2D sheet-like morphology and active sites of MnS2 are created on the porous carbon surface. Among all synthesized materials, CS_8/1 has shown high surface area of 971 m . Cyclic voltammetry results of all electrodes show a pseudocapacitive behavior. The CS_8/1 electrode exhibits ultra-high specific capacitance of 1194 F g 2 -1 g at 1080 W kg -1 -1 at 1 A g and specific energy of 214.89 Wh kg -1 -1 . Furthermore, the CS_8/1 electrode has shown exceptional cyclic stability with specific capacitance retention of 82% after 5000 cycles. EIS measurements show the charge transfer resistance Rct to be as minimum as 0.96 Ω for CS_8/1 electrode. Mn and S ions play important role in boosting the charge transfer and ultimately promoting pseudocapacitive properties with capacitive controlled reaction kinetics percentage as high as 94%. This improved performance is attributed to the synergistic impact of Mn ions paired with Co ions, as well as increased redox reaction and structural rearrangements.