Thermodynamic guidelines for the design of bimetallic catalysts for oxygen electroreduction and rapid screening by scanning electrochemical microscopy.: M-Co (M: Pd, Ag, Au)
Thermodynamic guidelines for the design of bimetallic catalysts for oxygen electroreduction and rapid screening by scanning electrochemical microscopy.: M-Co (M: Pd, Ag, Au)
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DOI：
10.1021/ja0449729
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发表时间：
2005-01-12
影响因子：
15
通讯作者：
Bard, AJ
中科院分区：
文献类型：
--
作者：
Fernández, JL;Walsh, DA;Bard, AJ
我们提出了用于酸性介质中氧还原反应（ORR）的改进双金属（及相关）电催化剂的设计指南。本指南基于简单的热力学原理，假设一种简单的机制，其中一种金属破坏分子 O-2 的氧-氧键，而另一种金属则起到还原所吸附的原子氧的作用。对这两个反应的吉布斯自由能的分析指导了金属组合的选择，这些金属组合可以产生与组成金属相比具有增强的 ORR 活性的合金表面。所选系统已通过制造金属催化剂阵列进行了测试，该金属催化剂阵列由沉积在玻璃碳（GC）基底上的 Pd、Au、Ag 和 Co 的各种二元和三元组合组成。使用扫描电化学显微镜 (SECM) 以新的快速成像模式检查这些材料在酸性介质中的 ORR 电催化活性。这用于快速筛选涵盖各种催化剂组合物的阵列，以确定其在 0.5 M H2SO4 中的 ORR 活性。使用 SECM 技术，我们已经确定了与纯金属成分相比具有增强电催化活性的金属组合。在 Pd、Au 和 Ag 中添加 Co 明显降低了 ORR 过电势，与所提出的模型一致。然后使用经典的旋转盘电极 (RDE) 实验检查在 SECM 筛选技术中表现出增强的电催化活性的催化剂点。炭黑负载的催化剂混合物在 GC RDE 上的活性和使用 SECM 筛选技术测定的电催化活性表现出极好的一致性。 C/Pd-Co 电极（10-30% Co）表现出显着的 ORR 催化活性，接近碳负载的 Pt。
We propose guidelines for the design of improved bimetallic (and related) electrocatalysts for the oxygen reduction reaction (ORR) in acidic media. This guide is based on simple thermodynamic principles assuming a simple mechanism where one metal breaks the oxygen-oxygen bond of molecular O-2 and the other metal acts to reduce the resulting adsorbed atomic oxygen. Analysis of the Gibbs free energies of these two reactions guides the selection of combinations of metals that can produce alloy surfaces with enhanced activity for the ORR when compared to the constituent metals. Selected systems have been tested by fabricating arrays of metallic catalysts consisting of various binary and ternary combinations of Pd, Au, Ag, and Co deposited on glassy carbon (GC) substrates. The electrocatalytic activity of these materials for the ORR in acidic medium was examined using scanning electrochemical microscopy (SECM) in a new rapid-imaging mode. This was used to rapidly screen arrays covering a wide range of catalyst compositions for their activity for the ORR in 0.5 M H2SO4. Using the SECM technique, we have identified combinations of metals with enhanced electrocatalytic activities when compared with the constituent, pure metals. Addition of Co to Pd, Au, and Ag clearly decreases the ORR overpotential, in agreement with the proposed model. Catalyst spots that exhibited enhanced electrocatalytic activity in the SECM screening technique were then examined using classical rotating disk electrode (RDE) experiments. The activity of carbon black supported catalyst mixtures on a GC RDE and the electrocatalytic activity determined using the SECM screening technique showed excellent agreement. C/Pd-Co electrodes (10-30% Co) exhibited remarkable activity for ORR catalysis, close to that of carbon-supported Pt.