| In-situ hybridizations of conducting polymer polyaniline (PANI) and manganese oxidesγ-MnO2, nonstoichiometric MnOx, nm-MnO2 (manganese dioxide nanoparticles) and nm-ND42-MnO2 (ND42,N-[(triethoxysilyl)methyl]aniline, grafted manganese dioxide nanoparticles) were conducted electrochemically in this thesis. Composite films PANI/y-MnO2 and PANI/MnOx in fibrous structures and PANI/nm-MnO2 and PANI/nm-ND42-MnO2 in 3D granular structures were obtained. Characterizations of the films were conducted by X-ray diffraction (XRD), X-ray photo-electron spectroscope (XPS) and scanning electron microscope (SEM). Electrochemical and pseudocapactive properties of the films were studied by cyclic voltammetry and constant current charging-discharging experiments. Symmetric model capacitors were constructed using the films as electrodes.In-situ hybridization of PANI andγ-MnO2 was realized in 0.5 mmol·L-1 H2SO4 based on electropolymerization of aniline and electrochemical oxidation of Mn2+, which leading to The obtained composite film PANI/γ-MnO2 showed fibrous morphologies due to effective control of secondary growth of the polymer chains, resulted from the adjustment of chemical environment of aniline polymerization by the in-situ deposition ofγ-MnO2. PANI/γ-MnO2 displayed characteristic redox peaks of PANI on cyclic voltammogram measured in acidic aqueous solution. The XRD patterns of PANI/γ-MnO2 showed characteristic peaks ofγ-MnO2, while peaks characteristic of Mn(IV) appeared on Mn 3s XPS spectrum of the composite film. Composite film PM250 obtained from the solution containing 50 mM Mn2+ and 0.4 M aniline demonstrated a specific capacitance of 532 F/g measured through charging-discharging at 2.4 mA/cm2 in 1.0 mol·L-1 NaNO3 (adjust pH to 1), which is 26 % higher than that of similarly prepared PANI. PM250 kept 76% of its capacitance after 1200 cycles of charging-discharging at 5.0 mA/cm2 with a coulombic efficiency(η) of 97.5%.The symmetric capacitor using PM250 as the electrodes showed a capacitance of 124 F/g measured at 2.4 mA/cm2.Nonstoichiometric MnOx was obtained from Mn2+ in neutral aqueous solutions (pH 5.6) electrochemically together with PANI. Composite films PANI/MnOx were obtained in fibrous structures by this in-situ electrochemical co-deposition. There was no distinguished peak on XRD pattern of the composite film, revealing the amorphous nature of MnOx in the film. Manganese existed in a mixed oxidation states of +2,+3 and+4 in the film, based on XPS measurement. The composite films showed good pseudocapacitive behaviors in 1.0 mol·L-1 NaNO3 (pH=1) between 0 to 0.65 V.Composite film PMx120 obtained from the solution of 120 mM Mn2+ showed a specific capacitance of 588 F/g, which is 44 % higher than that of similarly prepared PANI (408 F/g) measured at 1.0 mA/cm2.PMx120 kept 90.3 % of its capacitance after 1000 charging-discharging cycles, with a coulombic efficiency of 98%.The specific capacitance of a symmetric capacitor using PMx120 as the electrodes was 112 F/g measured at 3.0 mA/cm2.In-situ electrochemical co-depositons of PANI and manganese dioxide nanoparticles, nm-MnO2, or ND42 grafted nanoparticles, nm-ND42-MnO2 were conducted to afford composite films of PANI/nm-MnO2 and PANI/nm-ND42-MnO2. Due to effective nanoparticle-template-guiding, composite film PANI/nm-ND42-MnO2 obtained from the ND42 modified nanoparticles showed uniform 3D granular structure and modified pseudocapacitive properties. PANI/nm-ND42-MnO2 displayed a specific capacitance of 421 F/g measured at 1.0 mA/cm2, while the specific capacitance of PANI/nm-MnO2 obtained from the neat nanoparticles was 358 F/g. Both of the composite films showed higher specific capacitance than similarly prepared PANI (143 F/g). Symmetric capacitors using composite films PANI/nm-ND42-MnO2 and PANI/nm-MnO2 as the electrodes, respectively were constructed. The specific capacitances of the capacitors were 84.5 and 58.3 F/g, respectively measured at 1.0 mA/cm2.
|
PDF Full Text Request