J. Phys. Chem. C 2008, 112, 4961-4970
4961
Characterization of Ligand Effects on Water Activation in Triarylphosphine-Stabilized Pt Nanoparticle Catalysts by X-ray Absorption Spectroscopy Daniel S. Gatewood,†,‡ Terence L. Schull,† Olga Baturina,§ Jeremy J. Pietron,† Yannick Garsany,† Karen E. Swider-Lyons,† and David E. Ramaker*,†,‡ Chemistry DiVision, NaVal Research Laboratory, Washington, District of Columbia 20375, Chemistry Department, George Washington UniVersity, Washington, District of Columbia 20052, and NoVa Research, Incorporated, Alexandria, Virginia 22308 ReceiVed: October 1, 2007; In Final Form: December 19, 2007
The synthesis, preparation, and electrochemical characterization of triphenylphosphine triphosphonate (TPPTP) stabilized Pt particles have been reported previously with the observation that the TPPTP ligands increase the specific activity of Pt for the oxygen reduction reaction (ORR). In this work the ORR activity of the Pt/ TPPTP electrocatalyst is probed by analyzing water activation with Pt L3-edge X-ray absorption spectroscopy and the EXAFS and Delta XANES analysis techniques. The results are compared with that for similarly prepared Pt/C and Pt stabilized by an oxidized TPPTP ligand (Pt/ox-TPPTP). The Pt particles in the Pt/ TPPTP catalyst at 0.54 V (RHE) are complexed via the P (i.e., Pt-P
