Electrochemical Synthesis of Polyaniline on Nanodiamond Powder

Conductive polyaniline (PANI) was electropolymerised on undoped nanodiamond (ND) powder by potentiodynamic deposition in sulphuric acid solution containing aniline monomer. The influences of anodic potential limit and concentrations of aniline monomer and H2SO4 on cyclic voltammetry behaviour were investigated. The results showed that PANI was deposited on the ND powder electrode under an anodic potential limit of 1.1-1.5 V. However, a high anodic potential above 1.0 V was only necessary to initiate the polymerisation in initial cycles, so PANI was further grown from –0.2 to 0.9 V to avoid overoxidation and degradation. The PANI growth rate increased with the increasing concentrations of aniline monomer and H2SO4, but it decreased when the monomer concentration was higher than 0.3 M. Fourier transform infrared spectrum and scanning electron microscope confirmed the presence of PANI. At the initial polymerisation, the PANI nanoparticles were deposited on the ND surfaces. The fibril PANI increased during further growth and linked the ND particles together, forming a porous network structure. The impedance of the PANI/ND electrode was far lower than that of the ND powder electrode. The composite electrode demonstrated higher conductivity and better capacitance behaviour.