In Situ Probing of the Active Site Geometry of Ultrathin Nanowires for the Oxygen Reduction Reaction
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- 作者：Haiqing Liu ; Wei An ; Yuanyuan Li ; Anatoly I. Frenkel ; Kotaro Sasaki ; Christopher Koenigsmann ; Dong Su ; Rachel M. Anderson ; Richard M. Crooks ; Radoslav R. Adzic ; Ping Liu ; Stanislaus S. Wong
- 刊名：Journal of the American Chemical Society
- 出版年：2015
- 出版时间：October 7, 2015
- 年：2015
- 卷：137
- 期：39
- 页码：12597-12609
- 全文大小：689K
- ISSN：1520-5126
文摘
To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (鈭? nm) core鈥搒hell Pt鈭糚d9Au nanowires, which have been previously shown to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu鈭糚d configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Hence, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.