Abstract
The oxygen reduction reaction (ORR) activity and stability of platinum (Pt) and PtM (M = Ni, Co, Cr, Pd) supported on polyaniline/carbon nanotube (PtM/PANI-CNT) were explored and compared with the commercial Pt/C catalyst (ETEK). The Pt/PANI-CNT catalyst exhibited higher ORR activity and stability than the commercial Pt/C catalyst even though it had larger crystallite/particle sizes, lower catalyst dispersion and lower electrochemical surface area (ESA), probably because of its high electrical conductivity. The addition of second metal (M) enhanced the ORR activity and stability of the Pt/PANI-CNT catalyst, because the added M induced the formation of a PtM alloy and shifted the d-band center to downfield, leading to a weak chemical interaction between oxygenated species and the catalyst surface and, therefore, affected positively the catalytic activity. Among all the tested M, the addition of Cr was optimal. Although it improved the ORR activity of the Pt/PANI-CNT catalyst slightly less than that of Pd (around 4.98%) in low temperature (60 °C)/pressure (1 atm abs), it reduced the ESA loss by around 14.8% after 1000 cycles of repetitive cyclic voltammetry (CV). In addition, it is cheaper than Pd metal. Thus, Cr was recommended as the second metal to alloy with Pt on the PANI-CNT support.
Highlights
Among the several types of fuel cells, proton exchange membrane (PEM) fuel cells are one of the most attractive types because they possess several advantages, including a high efficiency, clean operation and rapid start-up and shut-down
Among various types of support materials, carbon black (Vulcan XC-72) has been used widely in PEM fuel cells because of its high electrical conductivity and high specific surface area [2,3], but it suffers from electrooxidation under fuel cell operating conditions resulting in the loss of catalytic activity after long-term operation [4,5]
The wrapping of carbon nanotubes (CNTs) with polyaniline (PANI), which can serve as a dispersant and stabilizer for immobilizing of Pt NPs, led to enhanced surface properties, such as the electrical conductivity, chemical resistance and surface area [18,19,20]
Summary
Among the several types of fuel cells, proton exchange membrane (PEM) fuel cells are one of the most attractive types because they possess several advantages, including a high efficiency, clean operation and rapid start-up and shut-down. The surface of CNTs is inert and hydrophobic, giving a poor compatibility with metal nano-particles (NPs) Their surface is usually modified prior to use to improve the surface chemistry/property for immobilizing the metal catalyst NPs. The most common surface modification method to create functional groups on the surface of the CNTs is the acid treatment [8,9,10]. The wrapping of CNTs with polyaniline (PANI), which can serve as a dispersant and stabilizer for immobilizing of Pt NPs, led to enhanced surface properties, such as the electrical conductivity, chemical resistance and surface area [18,19,20]. The novelty of this work is the comparative study of the ORR activity and stability of several Pt alloy catalysts supported on the polyaniline-wrapped carbon nanotube, which had never been studied before
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
