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首页> 外文期刊>Chemistry: A European journal >Chemical dealloying mechanism of bimetallic pt-co nanoparticles and enhancement of catalytic activity toward oxygen reduction
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Chemical dealloying mechanism of bimetallic pt-co nanoparticles and enhancement of catalytic activity toward oxygen reduction

机译：双金属pt-co纳米粒子的化学脱金属机理及对氧还原的催化活性增强

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摘要

The chemical dealloying mechanism of bimetallic Pt-Co nanoparticles (NPs) and enhancement of their electrocatalytic activity towards the oxygen reduction reaction (ORR) have been investigated on a fundamental level by the combination of X-ray absorption spectroscopy (XAS) and aberration-corrected scanning transmission electron microscopy (STEM). Structural parameters, such as coordination numbers, alloy extent, and the unfilled d states of Pt atoms, are derived from the XAS spectra, together with the compositional variation analyzed by line-scanning energy-disper- sive X-ray spectroscopy (EDX) on an atomic scale, to gain new insights into the dealloying process of bimetallic PtCo NPs. The XAS results on acid-treated Pt-Co/C NPs reveal that the Co-Co bonding in the bimetallic NPs dissolves first and the remaining morphology gradually transforms to a Pt-skin structure. From cyclic voltammetry and mass activity measurements, Pt-Co alloy NPs with a Pt-skin structure sig- niticantly enhance the catalytic performance towards the ORR. Further, it is observed that such an imperfect Ptskin surface feature will collapse due to the penetration of electrolyte into layers underneath and cause further dissolution of Co and the loss of Pt. The electrocatalytic activity decreases accordingly, if the dealloying process lasts for 4h. The findings not only demonstrate the importance of appropriate treatment of bimetallic catalysts, but also can be referred to other Pt bimetallic alloys with transition metals.
机译：通过X射线吸收光谱（XAS）和像差校正的结合，从根本上研究了双金属Pt-Co纳米颗粒（NPs）的化学脱金属机理及其对氧还原反应（ORR）的电催化活性的增强。扫描透射电子显微镜（STEM）。从XAS光谱中得出结构参数，例如配位数，合金范围和Pt原子的未填充d状态，以及通过线扫描能量色散X射线光谱仪（EDX）分析的组成变化。原子尺度，以获得对双金属PtCo NP脱合金过程的新见解。酸处理的Pt-Co / C NP的XAS结果表明，双金属NP中的Co-Co键首先溶解，其余形态逐渐转变为Pt皮肤结构。通过循环伏安法和质量活度测量，具有Pt皮肤结构的Pt-Co合金NPs显着提高了对ORR的催化性能。此外，已经观察到，由于电解质渗透到下面的层中，这种不完善的Ptskin表面特征将崩溃，并导致Co的进一步溶解和Pt的损失。如果脱合金过程持续4h，则电催化活性相应降低。这些发现不仅证明了适当处理双金属催化剂的重要性，而且还可以用于其他含过渡金属的Pt双金属合金。

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