Functionalization Of Carbon Electrode And Subsequent Electrochemical Deposition Of Nanostructured Manganese Oxide

Manganese Oxide (MnO2) is one of the most promising pseudocapacitive materials due to its low cost, environmental friendliness and high theoretical specific capacitance. Current collector is also very important for supercapacitor operation. In this paper, functionalization of carbon cloth current collector (CC) is conducted in H2SO4 aqueous solution. Firstly, functional carbon cloth (FCC) is fabricated by cyclic voltammetry (CV), ranging from 0 V (vs. SCE) to different upper potential limits. Secondly, reduced functional carbon cloth (RFCC) is prepared by CV, ranging from different lower potential limits (lower than 0 V) to 2.5 V (vs. SCE). Surface image investigation by scanning electron microscope (SEM), contact angle measurements and CV are conducted to investigate the properties of the functionalized carbon cloth electrodes. We find that the wettability and the electrochemical activity of the carbon electrode can be significantly improved by functionalization. However, its morphology is not so much influenced.Electrochemical deposition of nanostructured manganse oxide is conducted on RFCC in a solution of containing 0.125 M (NH4)2SO4 and 0.25 M NaAc to afford MnO2/RFCC, and in the above solution with 0.125 M (NH4)2SO4 added to afford N-MnO2/RFCC. Morphologies and crystalline sructure of MnO2/RFCC and N-MnO2/RFCC are studied by SEM and X-ray diffraction (XRD). It is found that MnO2 are deposited on RFCC in nanoparticles and the size of nanoparticles can be further decreased by adding (NH4)2SO4 in the electrodepostion solution. XRD results show that the as-synthesized MnO2 which is electrochemically deposited on CC, FCC and RFCC is a-MnO2 with 1×1 and 2×2 tunnel structures. The electrochemical performances of MnO2/CC, N-MnO2/CC, MnO2/RFCC and N-MnO2/RFCC are studied by CV and galvanostatic charge/discharge (CP). The specific capacitances of N-MnO2/RFCC, MnO2/RFCC, N-MnO2/CC and MnO2/CC are 450,345.5,323.5 and 273.3 F/g at the current density of 1 A/g, respectively. When the current density increases 20 times from 1 A/g to 20 A/g, the specific capacitance of 304.3 F/g can be maintained for N-MnO2/RFCC. Furthermore, the cyclic charge/discharge stability of N-MnO2/RFCC can be improved by the addition of (NH4)2SO4 in the electrodeposition solution.