Characterization of Ligand Effects on Water Activation in Triarylphosphine-Stabilized Pt Nanoparticle Catalysts by X-ray Absorption Spectroscopy
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- 作者：Daniel S. Gatewood ; Terence L. Schull ; Olga Baturina ; Jeremy J. Pietron ; Yannick Garsany ; Karen E. Swider-Lyons ; David E. Ramaker
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：April 3, 2008
- 年：2008
- 卷：112
- 期：13
- 页码：4961 - 4970
- 全文大小：504K
- 年卷期：v.112,no.13(April 3, 2008)
- ISSN：1932-7455
文摘
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 thespecific 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 spectroscopyand the EXAFS and Delta XANES analysis techniques. The results are compared with that for similarlyprepared 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<tp) with about 0.3 ML of TPPTP.Approximately one-half of this converts to a Pt-O-P<tp linkage at 1.0 V; these species exist on the surfacealong with a dramatically reduced OH coverage. The reduction in OH coverage enhances the surface-specific(ORR) rate relative to the same-sized Pt particles on carbon. The Pt/ox-TPPTP catalysts are linked via a3-fold coordinated Pt
O-P<tp, which severely blocks sites and makes the electrocatalysts almost inactiveto water activation and the ORR. The relative importance of site blocking, hydrophobic effects, and electroniceffects are discussed with hydrophobic effects believed to dominate in the Pt/TPPTP catalyst and site blockingin the Pt/ox-TPPTP catalyst.
O-P<tp, which severely blocks sites and makes the electrocatalysts almost inactiveto water activation and the ORR. The relative importance of site blocking, hydrophobic effects, and electroniceffects are discussed with hydrophobic effects believed to dominate in the Pt/TPPTP catalyst and site blockingin the Pt/ox-TPPTP catalyst.