Impact of Structure and Composition on the Dealloying of CuxAu(1–x) Bulk and Nanoscale Alloys

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• 作者：Jiaxin Xia ; Stephen Ambrozik ; Cameron C. Crane ; Jingyi Chen ; Nikolay Dimitrov
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：February 4, 2016
• 年：2016
• 卷：120
• 期：4
• 页码：2299-2308
• 全文大小：621K
• ISSN：1932-7455

文摘

In this work, the impact of structure and composition on the dealloying of bulk and nanoscale alloys Cu_xAu_(1–x) have been discussed. In comparison with the dealloying of Ag—Au alloys, the Cu—Au system exhibits dealloying curves with more features associated generally with multistage dealloying. It has been shown for the first time that three stages exist during dealloying process of bulk Cu_xAu_(1–x) (x = 0.7 and 0.8) alloys. The dealloying critical potential, E_c, has been associated with the starting point of stage II in which the anodic current slowly increases. Analysis of data from this work along with results of others suggests a monotonic potential dependence of E_c upon the composition of bulk Cu_xAu_(1–x) alloys in the range of x from 0.70 to 0.95. The dealloying behavior of Cu_0.75Au_0.25 (Cu₃Au) intermetallic (length ～19 nm, width ～10 nm) and random alloy (length ～23 nm, width ～9 nm) nanorods have also been discussed. Very close values of E_c have been determined for both types of nanorods with the random alloy dealloying at slightly more negative potentials (c.a. 15–20 mV) than the intermetallic. In addition, both Cu₃Au nanorods feature close to 200 mV lower E_c than bulk alloys with identical composition. Formic acid oxidation tests reveal that the catalysts generated by platinization of as-synthesized and dealloyed nanorods exhibit very good activity with peak current densities in the range of 3.5 to 5.5 mA.cm^–2. Both catalysts withstand testing of more than 1500 cycles. Overall, the results of this study demonstrate unique aspects of Cu_xAu_(1–x) dealloying and ascertain the feasibility of nanosized frameworks (dealloyed structures or nanoparticles) as catalyst supports in fuel cell applications.