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首页> 外文期刊>Journal of Materials Chemistry, A. Materials for energy and sustainability >Charting the relationship between phase type-surface area-interactions between the constituent atoms and oxygen reduction activity of Pd-Cu nanocatalysts inside fuel cells by in operando high-energy X-ray diffraction
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Charting the relationship between phase type-surface area-interactions between the constituent atoms and oxygen reduction activity of Pd-Cu nanocatalysts inside fuel cells by in operando high-energy X-ray diffraction

机译：在Operando高能量X射线衍射中绘制燃料电池内部燃料电池内部PD-Cu纳米催化剂的组分型和氧还原活性的相位表面积相互作用的关系

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摘要

The activity and stability of nanoalloy catalysts for chemical reactions driving devices for clean energy conversion, in particular the oxygen reduction reaction (ORR), depend critically on optimizing major structural characteristics of the nanoalloys, such as the phase composition, surface area and bonding interactions between the constituent atoms, for the harsh operating conditions inside the devices. The effort requires good knowledge of the potential effect of changes in these characteristics on the catalytic functionality of the nanoalloys and, hence, on the devices' performance. We present the results from an in operando high-energy X-ray diffraction (HE-XRD) study on the concurrent changes in the structural characteristics and ORR activity of Pd-Cu nanoalloy catalysts as they function at the cathode of a proton exchange membrane fuel cell (PEMFC). We find that the as-prepared Pd-Cu nanoalloys with a chemical composition close to Pd1Cu1 are better ORR catalysts in comparison with Pd1Cu2, i.e. Pd-poor, and Pd3Cu1, i.e. Pd-rich, nanoalloys. Under operating conditions though, the former suffers a big loss in ORR activity appearing as a slow-mode oscillation in the current output of the PEMFC. Losses in ORR activity suffered by the latter also exhibit sudden drops and rises during the PEMFC operation. Through atomic pair distribution function (PDF) analysis of the in operando HE-XRD data, we identify the structural changes of Pd-Cu alloy NPs that are behind the peculiar decay of their ORR activity. The results uncover the instant link between the ever-adapting structural state of ORR nanocatalysts inside an operating PEMFC and the performance of the PEMFC. Besides, our results indicate that, among others, taking control over the intra-particle diffusion of metallic species in nanoalloy catalysts may improve the performance of PEMFCs significantly and, furthermore, in operando HE-XRD can be an effective tool to guide the effort. Finally, we argue that, though showing less optimal ORR activity in the as-prepared state, monophase Pd-Cu alloy catalysts with a composition ranging between Pd1Cu1 and Pd3Cu1 may deliver optimal performance inside operating PEMFCs.
机译：用于清洁能量转化的化学反应驱动装置的纳米铝催化剂的活性和稳定性，特别是氧还原反应（ORR），尺寸依赖于优化纳米合金的主要结构特性，例如相位组成，表面积和粘合相互作用组成原子，用于设备内的苛刻操作条件。努力需要良好地了解这些特征变化对纳米合金的催化功能的潜在效果，因此在装置的性能下。我们在Operando高能量X射线衍射（HE-XRD）研究中介绍了PD-Cu纳米合金催化剂的结构特性和ORR活性的同时变化的结果，因为它们在质子交换膜燃料的阴极上起作用细胞（PEMFC）。我们发现，与PD1CU1接近PD1CU1的化学成分的制备的PD-Cu纳米合金是与PD1Cu2，即Pd-POR和PD3CU1相比的更好的ORR催化剂，即PD-Rich，NaNoolloys。然而，在运行条件下，前者在ORR活动中遭受巨大损失，其出现在PEMFC的当前输出中的慢模式振荡。后者遭受的ORR活动的损失也表现出突然下降并在PEMFC操作期间上升。通过原子对分布函数（PDF）分析在Operando HE-XRD数据中，我们确定了PD-Cu合金NPS的结构变化，这是他们的orr活动的特殊衰减。结果揭示了在操作PEMFC内部的orr纳米催化剂的orr纳米催化剂的不良结构状态和PEMFC的性能之间的即时联系。此外，我们的结果表明，在纳米合金催化剂中控制金属物种的颗粒内扩散可以显着提高PEMFC的性能，而且，在Operando He-XRD中可以是指导努力的有效工具。最后，我们认为，尽管在制备状态下显示较少的最佳ORR活性，但是具有PD1CU1和PD3CU1之间的组合物的单相PD-Cu合金催化剂可以在操作PEMFC中提供最佳性能。

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