Kinetics of CO Poisoning in Simulated Reformate and Effect of Ru Island Morphology on PtRu Fuel Cell Catalysts As Determined by Operando X-ray Absorption Near Edge Spectroscopy

摘要

In situ X-ray absorption spectroscopy (XAS) measurements, including both X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS), were carried out on commercially produced Pt and PtRu bimetallic electrocatalysts as well as on a mechanically mixed PtRu bimetallic electrocatalyst in an operating fuel cell in H2 doped with 150 ppm CO. By use of the novel XANES technique, the coverages of CO and ontop and n-fold H (overpotential deposited and underpotential deposited hydrogen) are obtained and compared for the three catalysts, and the results are correlated with PtRu cluster morphology. The mechanical mixing process used to create the bimetallic PtRu catalyst is found to maximize CO tolerance, although the PtRu commercial electrocatalyst exhibits an increased electronic effect, most probably due to the presence of Ru(O)x islands at the catalyst surface. The mobility of the CO on both Ru and Pt is found to be sharply dependent on the CO coverage, decreasing dramatically beyond 0.4 fractional coverage.