Carbon fiber paper (CFP), carbon cloth, which are conductive materials are so important contributing the heavy weight to the whole device. More importantly, the stability of the metal current collectors are rather poor when used in aqueous-based supercapa citors since the corrosion of metal with anions of the electrolytes (e.g., NO3-, Cl-, SO42-) spontaneously occurs limiting the practical use of the aqueous-based supercapacitors. In fact, the diffusion of the electrolyte in water is much faster than that in organic solvents leading to higher specific power. CFP has many advantages suitably to be used as the conductive substrate or current collector including high flexibility, corrosive resistance, porosity, and conductivity.

In this work, the chemical surface functionalization of CFP (f-CFP) was finely tuned using a mixed acid treatment with keeping high bulk conductivity of the CFP. Interestingly, it is found that oxygen containing groups on the CFP surface can introduce the pseudocapacitance due to a surface redox reaction at a solid-liquid interface [1].

There are a number of advantages of using f-CFP as the conductive substrates. In this work, we electrodeposited PANI on hydrophilic functionalized carbon fiber paper (f-CFP) and used as the pseudocapacitors. The carboxyl and hydroxyl groups of the f-CFP can chemically interact via H-bonding with PANI leading to high stability of the subsequently as-fabricated pseudocapacitors. The as-fabricated pseudocapacitor devices of PANI/f-CFP electrodes in both aqueous and organic electrolytes exhibit high charge storage performances due to their high porosity, high electronic and ionic conductivities, and high stability [2].

Carbon and metal oxide fibers can be procuced by electrospining process of polymer fiber and then heat treatment. Electrospinning process is the preparation method of polymer fiber with diameter range from microfiber to nanofiber. Electrospinning equipment consists of a syringe, syringe pump, spinneret, current collector, and high voltage power supply.

Manganeses oxide-based materials are one of the great interesting materials for energy storage application because of their relatively low cost, low toxicity and environmental compatibility [3].
Recently, spinel type oxides from transition metals (such as AB₂O₄ type), particularly the cobalt-manganese oxide (MnCo₂O₄) with Fd3m space group had intensive attraction as an electrode material for electro-catalyst and advance energy storage devices due to its low cost, low toxicity, easy synthesis, and the key purpose is its good stability, and high electro-catalytic activity. While cobalt- based metal has high redox activity and reversibility. Manganese can provide good transporting electron providing higher capacitive capacitance. Additionally, the structure with mixed valance band gives better electronic conductivity, which can improve electron transfer between electrode and electrolyte, and high redox-reaction form solid-state redox exchanging between couple cations (Mn and Co), so the MnCo₂O₄ are appropriate to use as active materials for the supercapacitor. In addition, the theoretical capacitance of MnCo₂O₄ (3,620 F/g) is higher than its parent compound (3,590 F/g). The morphology of active materials extremely have an impact to the performance of a supercapacitor device, especially 1D nano-structure were prepared by electrospinning technique which can enhance the ions transfer rate and reduce diffusion path for charge. So, the MnCo₂O₄ are suitable candidate to use as active material for the supercapacitor.

      

FE-SEM images of (a) as-prepared fibers,(b) MnCo₂O₄ Nanotubular-fibers, and (c,d) TEM image of MnCo₂O₄ Nanotubular-fibers [(c) low magnification, (d) High magnification]