Perfluorosulfonic acid-functionalized Pt/carbon nanotube catalysts with enhanced stability and performance for use in proton exchange membrane fuel cells

To further improve lifetime and performance of carbon nanotube (CNT) supported Pt catalysts for proton exchange membrane fuel cells, perfluorosulfonic acid (PFSA) was introduced by a simple colloid route to functionalize Pt (PFSA-Pt/CNT) catalysts. Here the PFSA is available as a binder to tightly anchor Pt nano-particles onto the CNT surfaces, and as a proton conductor to increase the triple phase boundary zone of the catalysts. The prepared Pt nano-particles ranging from 2 to 5 nm in diameter are uniformly deposited on CNTs. A high catalytic activity of this novel composite catalyst was observed by both cyclic voltammetry and oxygen reduction reaction (ORR) measurements. The loss rate of the electrochemically active area of the PFSA-Pt/CNT catalyst decreases by a factor of two in comparison with that of the plain Pt/CNT catalyst. Meanwhile, a lower loss rate for the new catalyst was also observed by electrochemically-accelerated durability testing for the ORR activity. These results indicate that the stability of the new catalyst is significantly improved over that of the plain Pt/CNT catalyst by introduction of PFSA.

The perfluorosulfonic acid (PFSA) polymer was introduced to improve the lifetime and performance of CNT-supported Pt catalysts. We demonstrated that Pt nano-particles can be produced well-dispersed on the CNT surfaces, and the catalytic activity and stability of the resulting composite catalyst was greatly enhanced with additional PFSA.Figure optionsDownload as PowerPoint slideResearch highlights
► Compared to carbon black, the carbon nanotube (CNT) has high chemical stability and unique mechanical property, which could effectively decrease the support degradation.
► The introduction of perfluorosulfonic acid (PFSA) polymer greatly improves dispersion of metal particles on inert CNT surfaces by enhancing metal-support interaction.
► The PFSA polymer can enhance the catalytic activity of Pt catalysts by increasing the triple phase boundary reaction zone. Most significantly, the PFSA offers a strong metal-support interaction as both a binder and a stabilizer for Pt nano-particles, which further improves the CNT supported catalyst lifetime.