Synthesis of polyaniline-wrapped carbon nanotube-supported PtCo catalysts for proton exchange membrane fuel cells: activity and stability tests

Abstract

A series of the polyaniline (PAN)-wrapped carbon nanotube (CNT)-supported PtCo (PtCo/xPAN–CNT) catalysts was prepared for the oxygen reduction reaction (ORR) in a proton exchange membrane (PEM) fuel cell. The effect of the PAN content wrapped around the multiwall CNTs in the range of 0–15 wt% on the activity and stability of the PtCo catalysts was explored. Increasing the PAN content on the CNT surface did not significantly affect the Pt : Co ratio and catalyst loading on the CNT surface, while it positively affected the electrode conductivity, crystallite size, average particle size and the electrochemical surface area (ESA) as well as the hydrophilic property of the PtCo catalyst. Among all the prepared PtCo catalysts, PtCo/10PAN–CNT exhibited the highest catalytic activity towards the ORR, with a kinetic current density of 36.9 mA cm⁻² in 0.5 M H₂SO₄ and a current density of 407 mA cm⁻² at 0.6 V (244 mW cm⁻²) in a PEM fuel cell under a humidified H₂/O₂ environment at 60 °C and ambient pressure. The presence of PAN on the CNT surface can reconfigure the catalyst-support interaction, resulting in an increased catalyst stability.