Polyaniline (PANI), polyaniline doped with poly(styrene sulfonate) (PANI-PSS), polyaniline doped with gold (PANI-Au) as well as polyaniline co-doped with poly(styrene sulfonate) and gold (PANI-Au-PSS) have been prepared using the interfacial polymerization method under similar conditions. The morphology and chemical structure of the products were examined by scanning electron microscopy, UV-vis adsorption spectroscopy and Fourier transform infrared spectroscopy. Electrochemical techniques were used to study their electrochemical and electrocatalytic activities. The results demonstrate that PANI has the highest electrochemical activity in acidic solutions among the investigated species, while with the pH values increasing from pH 6.98 to 9.18, PANI-PSS and PANI-Au-PSS exhibit much better electrochemical activity than PANI and PANI-Au, indicating that PSS plays a vital role in improving the electro-activity of PANI in neutral and basic solutions. The doping of Au alone with PANI is not the same effective as the PSS in the enhancement of electrochemical and electrocatalytic activities, whereas the co-use of Au and PSS has a synergistic contribution on the improvement of electrocatalytic activity of PANI, and therefore the ternary PANI-Au-PSS composite exhibits the strongest electrocatalytic ability to the oxidation of ascorbic acid and the reduction of hydrogen peroxide in neutral solutions. (C) 2009 Elsevier B.V. All rights reserved.