摘要(英) |
In recent years, platinum (Pt) has been widely used as a catalyst and electrocatalyst. However, monometallic platinum is easily deactivated or poisoned during electrocatalytic processes. Among them, carbon monoxide (CO) is an obvious example. CO will adsorb on the surface of platinum, which probably occupy its active position and block the original path that could react. This phenomenon is called "CO poisoning". An anode catalyst that is resistant to CO poisoning is related to the efficiency of the fuel cell and has significant importance for future energy development.
This study is based on the bimetallic alloy Pt3Co(111) electrode, and its chemical composition and lattice arrangement are confirmed by photoelectron spectroscopy (XPS) and ray diffraction (XRD). After observing its surface structure with a scanning tunneling microscope (STM), we explore its ability of CO tolerance and electrochemical characteristics of catalytic hydrogen oxidation.
Compared with the Pt(111) electrode, the main peak of the single-layer carbon monoxide stripping on the Pt3Co(111) electrode shifted negatively by 0.06 V, and the charge of this oxidation wave is only 240 C/cm2, which is much lower than the 360 C/cm2 of the Pt(111) electrode. It means that adsorbed CO molecules do not completely cover the Pt3Co(111) electrode. This result is also consistent with the phenomenon that hydrogen atoms (Hupd) are still adsorbed on Pt3Co(111) between -0.25 and 0.05 V. Furthermore, Hupd will also affect the hydrogenation reaction current. Compared with Pt(111), the hydrogen oxidation current of the Pt3Co(111) electrode increases rapidly after removing Hupd.
STM results revealed that the surface of the Pt3Co(111) electrode is composed of broad terraces and monoatomic steps. c(4 x 2) structure formed by carbon monoxide adsorption was found on the platform, and its coverage was 0.5 (CO/Pt) lower than 0.75 of Pt(111), which is consistent with the above electrochemical results. In addition, Surface-Enhanced Infrared Absorption Spectroscopy (SEIRAS) results indicate that cobalt element in the inner layer of the electrode affects the strength and amount of carbon monoxide adsorbed on the platinum surface.
According to the calculation results of the Koutecký–Levich equation, the number of electrons transferred in the oxygen reduction reaction of the Pt3Co(111) electrode is 3.975, and it is speculated that oxygen is mainly reduced to water through the 4-electron pathway.
For the methanol oxidation reaction, the oxidation current generated by the Pt3Co(111) electrode is twice as large as that of Pt(111), and this activity can be attributed to the high tolerance of CO. |
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