Fabrication and properties of coral-like Ni/Mn-MOFs as electrode materials for supercapacitors

Metal organic frameworks (MOFs) have potential applications in the field of energy storage due to high specific surface area and rich porosity, and captured widely attention in recent years. In this work, nickel/manganese-based MOFs (Ni/Mn-MOFs) were successfully fabricated by solvothermal reaction using 1,4-phthalic acid as the organic ligand, nickel nitrate hexahydrate, and manganese nitrate tetrahydrate providing center metal ions. The Ni/Mn-MOFs were analyzed by scanning electron microscope, powder X-ray diffraction, and nitrogen absorption/desorption isotherm. The results indicate that the obtained Ni/Mn-MOFs have coral-like microstructures and hierarchical pores with a specific surface area of 380.8 m2/g and an average pore diameter of 13.6 nm. Subsequently, the Ni/Mn-MOFs were used as the electrode materials for supercapacitors, and the electrochemical properties were investigated in the three-electrode system using 6.0 M KOH aqueous solution as the electrolyte. The results show that the specific capacitances of the coral-like Ni/Mn-MOFs are 531.5 and 317.9 F/g at the current density of 0.5 and 5 A/g, respectively. And the capacitance retention is 67.7% after 2300 cycles at 5 A/g, which implies that the coral-like Ni/Mn-MOFs have higher specific capacitance and favorable cycle stability. The above results indicate that the coral-like Ni/Mn-MOFs facilitate the electrolyte infiltration and ions transportation.