In this study, the effect of oxygen on the potential of reduced polyaniline (PANI) was investigated. In order to enhance the air oxidation of reduced PANI, several composites of PANI doped with co-catalysts were prepared, and a reasonable flow Zn//PANI suspension cell system was designed to investigate the discharge capacity of obtained PANI composite microparticle suspension cathodes. Compared with PANI doped with Cu2+, La+, Mn2+ and zinc protoporphyrin, Ag doped PANI composite at 0.90 weight percent doping of Ag gave the highest value of discharge capacity for the half-cell potential from the initial value to -0.20 V (vs. SCE). A comparison study on the electrochemical properties of both PANI and Ag doped PANI microparticle suspension was done by using cyclic voltammetry, AC Impedance. Due to partial utilization of Zn//air fuel cell, the discharge capacity for Ag doped PANI reached 470 mA h g(-1) at the current density of 20 mA cm(-2). At 15 mA cm(-2), the discharge capacity even reached up to 1650 mA h g(-1) after 220 h constant current discharge at the final discharge voltage of 0.65 V. This work demonstrates an effective and feasible approach toward obtaining high energy and power densities by a Zn//Ag-doped PANI suspension flow battery system combined with Zn//air fuel cell. (C) 2014 Elsevier B.V. All rights reserved.