Remarkable electrochemical stability of one-step synthesized Pd nanoparticles supported on graphene and multi-walled carbon nanotubes

Abstract

Anodes and cathodes of fuel cells are usually composed of metallic nanoparticles (NPs) dispersed on carbon, in order to increase their active area. Since the degradation of the catalyst affects the performance of the fuel cells, understanding the stability of its components is pivotal to make these systems more reliable. As such, graphene sheets and carbon nanotubes have been employed as alternative supports to improve the stability of anodes in fuel cells. In this context, we have used polyvinylpyrrolidone (PVP) combined with a one-step chemical reduction induced by ethylene glycol to synthesize Pd NPs dispersed on chemically converted graphene (CCG). We compared the electrochemical stability of Pd NPs supported on carbon black (C), multi-walled carbon nanotubes (MWCNTs) and CCG. MWCNTs and CCG make Pd NPs electrochemically more stable than carbon black. Pd/CCG catalysts are more stable than Pd/MWCNTs during the first potential cycles, while Pd/MWCNTs showed a higher long-term stability. These results allow us to consider a competition between agglomeration of NPs and degradation of the support, where the agglomeration seems to be limited by the available surface area of the support.