Polyaniline doped with Cu²⁺ (PANI/Cu²⁺) was synthesized by cyclic voltammetry on the stainless steel mesh with various concentrations of copper sulfate (CuSO₄·5H₂O) in an electrolyte. The structure and morphology of PANI and PANI/Cu²⁺ films were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The electrochemical properties of PANI and PANI/Cu²⁺ films were investigated by cyclic voltammetry, galvanostatic charge–discharge testing and electrochemical impedance spectroscopy (EIS) in a 0.5 mol L⁻¹ H₂SO₄ electrolyte in a three-electrode system. The specific capacitance of the PANI/0.2 M Cu²⁺ film shows a larger specific capacitance of 618 F g⁻¹, lower resistance and better stability compared with the pure PANI film, although it is reduced to 340 F g⁻¹ after the first 100 cycles. Thus the good capacitive performance demonstrates its potential superiority for supercapacitors.

Phosphate and aluminate electrolytes were used to prepare plasma electrolytic oxidation (PEO) coatings on 6061 aluminum alloy. The surface and cross-section microstructure, element distribution, and phase composition of the PEO coatings were characterized by SEM, EDS, XPS, and XRD. The friction and wear properties were evaluated by pin-on-disk sliding tests under dry conditions. The corrosion resistance of PEO coatings was investigated by electrochemical corrosion and salt spray tests in acidic environments. It was found that the PEO coatings prepared from both phosphate and aluminate electrolytes were mainly composed of α-Al₂O₃ and γ-Al₂O₃. The results demonstrate that a bi-layer coating is formed in the phosphate electrolyte, and a single-layered dense alumina coating with a hardness of 1300 HV is realizable in the aluminate electrolyte. The aluminate PEO coating had a lower wear rate than the phosphate PEO coating. However, the phosphate PEO coating showed a better corrosion resistance in acidic environment, which is mainly attributed to the presence of an amorphous P element at the substrate/coating interface.

In this paper, γ -MnO ₂ was prepared via simple hydrothermal method and chosen to compound γ -MnO ₂ /polyaniline (PANI) composite electrode by in situ polymerization. The electrochemical performances of as-prepared samples were explored in acidic and neutral medium, respectively. And influenced its effects such as the different additions of composites, scan rates, and current densities in 0.5 M H ₂ SO ₄ electrolyte were further investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), respectively. The good capactive behaviours indicated that the γ -MnO ₂ in the conductive matrix of PANI restrains them from dissolution in acidic electrolyte, and PANI itself affords an additional electrochemical activity to the composite. A asymmetric supercapacitor was fabricated using γ -MnO ₂ /PANI as the positive electrode and activated carbon (AC) as the negative electrode. It displayed good capacitance performance of 232.1 F g ⁻¹ and high energy density 66.4 Wh kg ⁻¹ at a power density of 350.1 W Kg ⁻¹ , as well as good cycling life (maintaining 78.65% initial capacitance after 3000 cycles). The enhanced electrochemical performances implie that the γ -MnO ₂ /PANI composite can be potentially applied in superca-pacitors.