Mixed metallic NiFe / Mn‐MOF , and derived spinel Ni _{0. 5} Fe _{0 . 5} Mn ₂ O ₄ as high‐performance electrochemical electrodes

Abstract

Metal oxide/organic framework modification through mixing different metal ions is one of the most ingenious methods in material science. This study investigates elaborately designed bimetallic Fe/Mn, tri-metallic NiFe/Mn-metal organic frameworks, and their derived metal oxide nanocomposites for supercapacitor application. The novel bi- and tri-metallic MOFs have shown substantially different morphologies consisting of hexagonal bipyramid and interconnected sheets respectively. After calcination, the materials have altered to spinel FeMn2O4 and Ni0.5Fe0.5Mn2O4 with porous nanorods and hierarchical texture features respectively. The diverse morphologies with considerably large surface areas of the mixed metallic MOFs and the derived oxides make them efficient electrochemical electrodes. Ni incorporation also enhances the capacitive behavior of the electrodes and NiFe/Mn-MOF exhibits a superior specific capacitance of 1640 F g−1 at 1 A g−1. Furthermore, the FeMn2O4 and Ni0.5Fe0.5Mn2O4 nanostructures reveal highly stable capacitance with retention of 93 and 94% over 5000 cycles respectively. Besides, the assembled NiFe/Mn-MOF//AC asymmetric supercapacitor represents significant energy and power densities of 75 Wh kg−1 and 1166 W kg−1 at 1.5 A g−1 respectively. It also has relatively high stability with capacitance retention of 73% over 5000 cycles.