Activity enhancement of platinum electrocatalyst supported on functionalized carbon nanotubes by amide groups

Insufficient catalytic activity and durability are key barriers to the commercial deployment of low temperature polymer electrolyte membrane (PEM). On the other hand, oxygen reduction reaction (ORR) is one of the key processes of energy systems. The ORR sluggish kinetics requires a substantial amount of Pt, which has limited the scaling-up of technologies [1]. Recent observations suggest that carbon-based catalyst support materials can be doped with nitrogen to create strong, beneficial catalyst-support interactions which substantially enhance catalyst activity and stability. Pt-loading onto multi wall carbon nanotubes (MWCNTs) which has a large specific surface area and good conductivity has been reported as a successful approach for reducing the cost of catalysts [2,3]. In this study, Pt nanoparticles were placed on amide modified-MWCNTs (Pt/MWCNTs-A) and used as electrocatalyst for reduction of oxygen. Pt/MWCNT-A nanocomposite was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy and energy dispersive X-ray spectroscopy. After impregnation of catalyst ink on the gas diffusion layer, the electrodes were dried at 80oC for 8 h to form gas diffusion electrode (GDE). Catalyst coated membrane electrode (CCME) was prepared with hot pressing a Nafion 117 membrane and GDE having an active area of 0.785 cm2 with Pt/MWCNT catalysts of 0.5 mg cm-2 loading at the cathode side. The CCME is placed inside a homemade half-cell which is used as an ex situ method in fuel cell studies. The CCME electrochemical studies including polarization curves, EIS measurements, cyclic voltammetry and chronoamperometry were used to study electrochemical properties of obtained electrocatalyst. It was found that Pt/MWCNT-A was catalytically more active than Pt nanoparticles decorated on MWCNT. On the other hand, the Pt/MWCNT-A catalyst has satisfactory stability and improve catalytic activity in continues cycling makes it more attractive for fuel cell applications.