Preparation of MnOOH-graphene-foam Ni self-supported composite electrode and its supercapacitive performance

A self-supported electrode of MnOOH-graphene-foam Ni(NF) was synthesized by the method of vapor deposition and subsequent electrode position. Its physical properties including the phase, morphology and valence state were measured by the characterizations such as XRD, SEM and XPS, while the electrochemical performance was studied by constant current charge-discharge, cyclic voltammetry and the AC impedance technique. The results show that this method can be successfully used to prepare the self-supported MnOOH-graphene-NF electrode. The thin graphene layer is uniformly covered on the surface of NF, while the MnOOH microspheres are covered on the surface of graphene. The self-supported composite structure can be directly used as a supercapacitor electrode which shows great pseudocapacitance storage capacity in the electrolyte of 5 mol/L KOH. It can exhibit a large specific capacitance of 934 F/g at the current density of 0.5 A/g. When the current density increases to 5 A/g, the capacitance still remain at a high value of 771 F/g. The capacitance retention keeps at 98% after 5000 cycles at 2 A/g, and maintains a high coulombic efficiency close to 100%, indicating good supercapacitive performance. A new method was provided to synthesize the self-supported electrode of MnOOH-graphene-NF and it is expected to become a newly potential supercapacitor electrode material.