Electrochemical Quartz Crystal Nanobalance Analyses of Electrocatalysis for Fuel Cells

燃料电池电催化的电化学石英晶体纳米天平分析

基本信息

批准号：
13650881
负责人：
UCHIDA Hiroyuki
金额：
$ 2.24万
依托单位：
University of Yamanashi
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650881/
关键词：
Quartz Crystal Microbalance EQCM Electrocatalyst Fuel Cell Carbon Monoxide CO-Tolerance Oxygen Reduction Pt-Alloy

项目摘要

In order to find a clue for a design of high-performance electrocatalysts for fuel cells, we analyzed electrode reactions on Pt-Fe and Pt-Co alloy in comparison with that on pure Pt by using an electrochemical quartz crystal nanobalance (EQCN). We obtained the following results.1. We succeeded to construct 10MHz-EQCN system with a specially designed electrochemical cell, and confirmed the ultimate accuracy of ±0.1 Hz (±0.4 ng/cm^2) and high stability among long time.2. It was found that the Pt-Fe and Pt-Co electrodes were electrochemically stabilized by a formation of a few monolayers of Pt-skin layer during several repetitive potential sweeps in 0.1 M HClO_4 solution, i.e., a dissolution of alloy components followed by a rearrangement of thin Pt layer. The results obtained by XPS, ICP and EC-STM complement the EQCN results.3. A CO-tolerance at Pt-Fe and Pt-Co alloy electrodes was analyzed by the EQCN. In a positive-going potential scan at CO-adsorbed (θ_<co>=1) electrodes of pure Pt a … More nd Pt-Fe or Pt-Co alloy, a pre-oxidation peak (P_1) was observed at 0.3 to 0.5 V vs. RHE before a major CO oxidation peak (P_2) at 0.7 V. Each P_1 was assigned to an oxidation of weakly-adsorbed CO at Pt-Fe and Pt-Co alloys and adsorbed carboxylate at pure Pt, respectively. This is consistent with our previous results by in-situ FTIR, and strongly supports a modified electronic structure of the Pt-skin from that of pure Pt, which has been proposed by us. At P_2 region, CO is oxidized by OH formed by H_2O discharge and vacant sites on both of the electrodes formed by the oxidation of CO or CO-related species (COOH) are partly occupied by hydrated ClO_4 anions.4. Oxygen reduction reactions (ORR) at Pt, Pt-Fe, and Pt-Co electrodes in O_2-saturated 0.1 M HClO_4 solution were analyzed by the EQCN. At pure Pt, a constant amount of reaction intermediate such as Pt-O (ca. 20 %) always adsorbed on the surface even under high overvoltage. In contrast, the amount of such an intermediate was found to be fairly low at Pt-Fe and Pt-Co electrodes, probably due to a fast ORR kinetics. Such a difference between alloys and pure Pt may be ascribed to modified electronic structure of the Pt-skin. Less

为了为燃料电池高性能电催化剂的设计寻找线索，我们利用电化学石英晶体纳米天平（EQCN）对Pt-Fe和Pt-Co合金上的电极反应与纯Pt上的电极反应进行了比较。结果如下： 1.我们利用专门设计的电化学电池成功构建了10MHz-EQCN系统，并证实了最终的精度为±0.1 Hz（±0.4 ng/cm^2）和高稳定性。 2.发现Pt-Fe和Pt-Co电极在0.1 M HClO_4溶液中多次重复电位扫描期间通过形成一些单层Pt-皮层而实现电化学稳定，即溶解XPS、ICP 和 EC-STM 获得的结果补充了 EQCN 的结果。3． Pt-Fe 和 Pt-Co 合金电极通过 EQCN 对纯 Pt、Pt-Fe 或 Pt-Co 合金的 CO 吸附 (θ_<co>=1) 电极进行正向电位扫描进行分析。，在相对于 RHE 的 0.3 至 0.5 V 处观察到预氧化峰 (P_1)，然后在 0.7 V 处观察到主要 CO 氧化峰 (P_2)。每个 P_1分别归因于 Pt-Fe 和 Pt-Co 合金中弱吸附 CO 的氧化以及纯 Pt 中吸附羧酸盐的氧化，这与我们之前通过原位 FTIR 得到的结果一致，并且强烈支持了修改后的电子结构。由我们提出的纯Pt的Pt-皮在P_2区域，CO被H_2O放电形成的OH和形成的两个电极上的空位氧化。 CO或CO相关物质(COOH)的氧化部分被水合ClO_4阴离子占据。4．在O_2饱和的0.1 M HClO_4溶液中，在Pt、Pt-Fe和Pt-Co电极上进行了氧还原反应(ORR)。通过 EQCN 分析，在纯 Pt 中，恒定量的反应中间体如 Pt-O（约 20%）始终吸附在表面上。相反，在 Pt-Fe 和 Pt-Co 电极上，这种中间体的含量相当低，这可能是由于合金和纯 Pt 之间的快速 ORR 动力学差异所致。 Pt-皮肤的电子结构。