Nucleation of Platinum on Carbon Blacks

One of the outstanding challenges in the wider deployment of PEMFCs is improving the utilization of Pt. While decreasing particle size improves accessibility of the Pt, it also destabilizes the Pt particles and leads to dissolution/re-precipitation and rapid grain growth. A parameter that is as yet poorly characterized is the number of nucleation sites on the carbon support. Increased nucleation site density could provide a valuable approach to improve Pt utilization. In this work, nucleation density was characterized by determining the number of particles per nm2. A range of metal loadings were explored to investigate their effect on the number of Pt particles on three types of carbon support. It was concluded that the number of nucleation sites is relatively constant over the Vulcan family of carbon supports. However, activated carbons such as Norit SX-1G show much higher nucleation density.