PtCo₃ Nanoparticle-Encapsulated Carbon Nanotubes as Active Catalysts for Methanol Fuel Cell Anodes

Abstract

Noble metal alloys exhibit excellent catalytic activity in methanol oxidation reaction (MOR). However, noble metals are expensive and their synthesis is complicated. Thus, tremendous efforts have been devoted to reduce the noble metal content in catalyst alloys. In this study, a simple g-C3N4-assisted thermal method is used to synthesize PtCox nanoparticles encapsulated in carbon nanotubes (PtCox CNTs). Among all the investigated PtCox CNTs catalysts (x = 1, 1.5, 3, and 6), PtCo3 CNTs exhibit the highest catalytic activity in MOR because of their unique carbon structure, finely adjusted active site ratio, and suitable electronic states. The specific activity and mass activity of the PtCo3 CNTs are 4.4 and 7.7 times higher than those of commercial Pt/C, respectively. In addition, by increasing the amount of Co in PtCox CNTs, higher stability is achieved, and the catalytic activity of PtCo3 CNTs remains almost constant over 1500 cycles of an electrochemical test. Furthermore, the PtCo3 CNTs exhibit the highest current and power densities compared to other catalysts in a methanol fuel cell prototype. This study describes a simple method to synthesize Pt-based alloy nanoparticles with a low Pt ratio encapsulated in CNTs, which are highly active in MOR.