CO tolerance of Pt and PtSn intermetallic electrocatalysts on synthetically modified reduced graphene oxide supports

Pt and PtSn intermetallic nanoparticle (NP) catalysts were grown directly on various reduced graphene oxide (rGO) supports and were characterized by a combination of X-ray photoelectron spectroscopic (XPS), Raman microscopy, transmission electron microscopy (TEM), and powder X-ray diffraction (XRD) studies. Electrochemical CO stripping and rotating disk electrochemical (RDE) experiments showed the four rGO-PtSn catalysts to be superior to the four rGO-Pt catalysts for CO and CO-H2 electrooxidation in acidic solutions regardless of the rGO support, in agreement with earlier reports on PtSn NP electrocatalysts. For the four rGO-Pt catalysts, the rGO support causes a 70 mV spread in CO oxidation peak potential (ΔEpeak) and a 200 mV spread in CO-H2 electrooxidation onset. The more oxygenated graphenes show the lowest CO oxidation potentials and the best CO tolerance. For the four rGO-PtSn intermetallic catalysts, a ∼160 mV spread in CO-H2 electrooxidation onset is observed. With the exception of the nitrogen-doped graphene (NGO), a similar trend in enhanced CO electrooxidation properties with increasing oxygen content in the rGO support is observed. The NGO-PtSn electrocatalyst was superior to the other rGO-PtSn catalysts and showed the largest improvement in CO tolerance relative to the pure Pt system. The origin of this enhancement appears to stem from the unique rGO-PtSn support interaction in this system. These results are discussed in the context of recent theoretical and experimental studies in the literature.