New Approaches to In-situ X-Ray adsorption Spectroscopy of Pt-Ru Electrocatalysts Yuriy V. Tolmachev, Department of Chemistry, Kent State University #1 Unsupported metal catalysts can be modified with (sub)monolayers of other metal being in the powder by electrodeposition in suspension electrode configuration. Control of potential allows accurately tune surface composition and coverage. #2 Performance of core-shell Pt/Ru catalyst comparable with commercial alloyed nanoparticles and in some regimes even outperform it. #3 For the core-shell Pt/Ru catalyst studied with XAS three forms of ruthenium were identified two component system Ru(0) <=>Ru(III) in the range of potentials 0.05-0.95 and Ru(IV) at potentials higher than 1V. #4 Existence of underpotential Ru(III) oxides/hydroxides at the catalyst surface is proven in the wide range of potentials. PCA of Ru(III) content was correlated with the rates of potentiostatic methanol oxidation. #5 In the presence of methanol or CO keeps ruthenium in reduced Ru(0) state even at higher potentials. #6 In situ XAS data in the presence of methanol suggest that the reduction of Ru(OH)3 is faster than its formation between 0.30 and 0.50 V RHE. The situation is reversed at potentials higher than 0.50 V. #7 The irreversible formation of Ru(IV) upon exposure of the catalyst to potentials over 1.00 V causes degradation of the Ru promoting activity. Normalized CO stripping curves in 0.1M HClO4, v=10mV/s Potentiostatic currents of 1M MeOH oxidation, measured after 1800s Results of PCA analysis XAS spectra collected at anodic potential scan Number of neighbors Bond length, Å Catalyst at 0.05 V Catalyst at 0.95 V Ru-Ru 3.12 ± 1.70 2.73 ± 0.04 0.91 ± 0.65 2.68 ± 0.05 Ru-Pt 5.44 ± 1.70 2.70 ± 0.03 2.9 ± 1.5 2.69 ± 0.03 Ru-O 3.2 ± 1.3 2.02 ± 0.04 Core-shell PtRu(30%), 10nm