Sato Takako, Kunimatsu Keiji, Watanabe Masahiro, Uchida Hiroyuki
Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4 Takeda, Kofu 400-8510, Japan.
J Nanosci Nanotechnol. 2011 Jun;11(6):5123-30. doi: 10.1166/jnn.2011.4124.
The adsorption and oxidation of CO on commercial nanoparticle catalysts supported on carbon black (Pt/C, Pt3Co/C, PtRu/C) were examined at 23, 40, and 60 degrees C in 0.1 M HClO4 by use of in situ ATR-FTIR (attenuated total reflection Fourier-transform infrared) spectroscopy. Absorption bands for the adsorbed CO assigned to linear (atop) CO (CO(L)) and bridge CO (CO(B)) were observed around 2040 cm(-1) and 1850 cm(-1), respectively, at high CO coverage theta(CO) close to 0.8 on all three types of catalysts. The adsorption rates of both CO(L) and CO(B) at the initial stage were found to decrease in the order Pt/C > Pt3Co/C > PtRu/C, indicating that the interaction of CO with PtRu is weakest. The adsorption of CO on these catalysts resulted in the growth of a sharp O-H stretching band around 3630 to 3640 cm(-1), which was assigned to non-hydrogen-bonded water molecules (isolated H2O) co-adsorbed with CO. For the electrooxidation reaction of CO, PtRu/C exhibited the highest activity at all temperatures. It was confirmed that the dominant factor for determining CO oxidation activity was the onset potential for the oxidation of isolated H2O, E(onset)(H2O), to provide an oxygen species that is consumed in either a Langmuir-Hinshelwood mechanism (Pt/C, Pt3Co/C) or the bi-functional mechanism (PtRu/C). In addition, PtRu/C exhibited the weakest Pt-CO interaction. The values of E(onset)(H2O) at PtRu/C were lowest among the three catalysts from 23 to 60 degrees C. With increasing temperature, the E(onset)(H2O) at Pt/C and Pt3Co/C shifted to less positive potential, resulting in increased CO oxidation activity, while the shift in E(onset)(H2O) at PtRu/C was relatively small.
在0.1 M高氯酸中，于23、40和60摄氏度下，使用原位衰减全反射傅里叶变换红外光谱（ATR-FTIR）对负载在炭黑上的商用纳米颗粒催化剂（Pt/C、Pt3Co/C、PtRu/C）上CO的吸附和氧化进行了研究。在所有三种类型的催化剂上，当CO覆盖度θ(CO)接近0.8时，分别在2040 cm(-1)和1850 cm(-1)左右观察到归属于线性（顶位）CO（CO(L)）和桥式CO（CO(B)）的吸附CO的吸收带。发现初始阶段CO(L)和CO(B)的吸附速率均按Pt/C > Pt3Co/C > PtRu/C的顺序降低，这表明CO与PtRu的相互作用最弱。CO在这些催化剂上的吸附导致在3630至3640 cm(-1)附近出现尖锐的O-H伸缩带的增长，该带归属于与CO共吸附的非氢键合水分子（孤立的H2O）。对于CO的电氧化反应，PtRu/C在所有温度下均表现出最高活性。已证实，决定CO氧化活性的主要因素是孤立的H2O氧化为在Langmuir-Hinshelwood机理（Pt/C、Pt3Co/C）或双功能机理（PtRu/C）中消耗的氧物种的起始电位E(onset)(H2O)。此外，PtRu/C表现出最弱的Pt-CO相互作用。在23至60摄氏度下，PtRu/C的E(onset)(H2O)值在三种催化剂中最低。随着温度升高，Pt/C和Pt3Co/C的E(onset)(H2O)向更正电位移动，导致CO氧化活性增加，而PtRu/C的E(onset)(H2O)的移动相对较小。
