Capacitive properties of PANI/MnO2 synthesized via simultaneous-oxidation route

Polyaniline (PANI) and manganese dioxide (MnO2) composite (PANI/MnO2) was synthesized via a simultaneous-oxidation route. In this route, all reactants were dispersed homogenously in precursor solution and existed as ions and molecules, and involved reactions of ions and molecules generating PANI and MnO2 simultaneously. In this way, PANI molecule and MnO2 molecule contact each other and arrange alternately in the composite. The inter-molecule contact improves the conductivity of the composite. The alternative arrangement of PANI molecules and MnO2 molecules separating each other, and prevents the aggregation of PANI and cluster of MnO2 so as to decrease the particle size of the composite. The morphology, structure, porous and capacitive properties are characterized by scanning electron microscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, Branauer–Emmett–Teller test, thermogravimetric analysis, Fourier transform infrared spectroscopy, cyclic voltammetry, charge–discharge test and the electrochemical impedance measurements. The results show that MnO2 is predominant in the PANI/MnO2 composite and the composite exhibits larger specific surface area than pure MnO2. The maximum specific capacitance of the composite electrode reaches up to 320 F/g by charge–discharge test, 1.56 times higher than that of MnO2 (125 F/g). The specific capacitance retains approximately 84% of the initial value after 10,000 cycles, indicating the good cycle stability.

► PANI/MnO2 composite was synthesized by the simultaneous-oxidation route.
► Good contact in inter-molecule level between PANI and MnO2 improves the conductivity.
► The separation between PANI and MnO2 prevents the aggregation of nano-composite.
► The maximum specific capacitance of the PANI/MnO2 electrode is 320 F/g.
► The as-prepared PANI/MnO2 exhibits excellent cycle stability of 84% capacitance retention after 10,000 cycles.