Electrochemical Properties of an Atomically Dispersed Platinum Catalyst Formed on a Heat-treated Carbon Support

Improving the specific oxygen reduction reaction (ORR) activity (SOA) of platinum catalysts is a promising way to reduce the amount of platinum required for the cathode in polymer electrolyte fuel cells. In this study, we compared the SOA of Pt catalysts loaded on two types of Ketjen Black: pristine (KB) and a sample heat treated at 1500 8C (KB1500). In addition, we characterized the platinum deposited on the carbon and compared the durability of these catalysts against potential cycling. The platinum catalyst loaded on KB1500 (Pt/KB1500) showed doublet hydrogen adsorption peaks at 0.12 V vs. RHE, observed by cyclic voltammetry, and the formation of atomically disperse platinum catalysts, which formed a cloud-like distribution with platinum atoms. Such a cloud-like distribution has not been observed for Pt/KB previously, and the higher SOA of the Pt/ KB1500 catalyst was due to the presence of the finely dispersed cloud-like platinum species. The differences in the surface structure of the carbon supports were investigated using X-ray diffraction, Raman scattering, electron spin resonance, and temperature-programmed desorption. The characterization revealed that KB1500 has continuous larger graphitic layers with point defects and holes, whereas KB has smaller graphitic layers whose edge sites are decorated with oxygen functional groups and hydrogen atoms. The durability of Pt/KB1500 in potential cycling tests was determined by cyclic voltammetry between 0.6 and 1.0 V vs. RHE for 10,000 cycles. These measurements revealed the high SOA and survival of the characteristic hydrogen adsorption peak at 0.12 V vs. RHE.