Three-dimensional tracking and visualization of hundreds of Pt-Co fuel cell nanocatalysts during electrochemical aging.
Three-dimensional tracking and visualization of hundreds of Pt-Co fuel cell nanocatalysts during electrochemical aging.
复制标题
DOI：
10.1021/nl203920s
复制
发表时间：
2012-01
期刊：
影响因子：
10.8
通讯作者：
Yingchao Yu;H. Xin;R. Hovden;Deli Wang;Eric D. Rus;J. Mundy;D. Muller;H. Abruña
中科院分区：
文献类型：
--
作者：
Yingchao Yu;H. Xin;R. Hovden;Deli Wang;Eric D. Rus;J. Mundy;D. Muller;H. Abruña
我们提出了一种电子断层扫描方法，允许在电化学老化之前和之后识别数百个具有一对一对应关系的电催化剂纳米颗粒。这种方法使我们能够在三维空间中跟踪燃料电池碳载体上每个Pt-Co纳米催化剂的轨迹和形态。结合使用原子尺度的电子能量损失光谱成像，我们的实验能够将催化剂的性能退化与颗粒/颗粒间形态、颗粒-支撑相互作用和近表面化学成分的变化联系起来。我们发现，在正常的燃料电池工作条件下（从+0.6到+1.0 V的电位扫描，30,000次循环），催化剂的老化会导致纳米颗粒的粗化，主要是通过聚结，从而导致性能的丧失。所观察到的聚结事件被发现是在电位循环过程中纳米颗粒迁移到碳载体上的结果。该方法提供了纳米催化剂降解在质子交换膜燃料电池（pemfc）中如何发生的详细见解，并表明最小化颗粒运动可以潜在地减缓颗粒的粗化和相应的性能下降。
We present an electron tomography method that allows for the identification of hundreds of electrocatalyst nanoparticles with one-to-one correspondence before and after electrochemical aging. This method allows us to track, in three-dimensions, the trajectories and morphologies of each Pt-Co nanocatalyst on a fuel cell carbon support. In conjunction with the use of atomic-scale electron energy loss spectroscopic imaging, our experiment enables the correlation of performance degradation of the catalyst with changes in particle/interparticle morphologies, particle-support interactions, and the near-surface chemical composition. We found that aging of the catalysts under normal fuel cell operating conditions (potential scans from +0.6 to +1.0 V for 30,000 cycles) gives rise to coarsening of the nanoparticles, mainly through coalescence, which in turn leads to the loss of performance. The observed coalescence events were found to be the result of nanoparticle migration on the carbon support during potential cycling. This method provides detailed insights into how nanocatalyst degradation occurs in proton exchange membrane fuel cells (PEMFCs) and suggests that minimization of particle movement can potentially slow down the coarsening of the particles and the corresponding performance degradation.