Defects do Catalysis: CO Monolayer Oxidation and Oxygen Reduction Reaction on Hollow PtNi/C Nanoparticles
Defects do Catalysis: CO Monolayer Oxidation and Oxygen Reduction Reaction on Hollow PtNi/C Nanoparticles
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DOI：
10.1021/acscatal.6b01106
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发表时间：
2016-07-01
期刊：
影响因子：
12.9
通讯作者：
Maillard, Frederic
中科院分区：
文献类型：
--
作者：
Dubau, Laetitia;Nelayah, Jaysen;Maillard, Frederic
扩展的和纳米尺寸的表面的催化性能在很大程度上取决于它们表现出的结构缺陷的量和性质。然而，虽然步骤或吸附原子的影响可以用单晶来解开（“表面科学方法”），但以受控的方式在纳米材料上可重复地实施结构缺陷仍然几乎不可行。一个值得特别关注的案例是纳米材料，它被用来催化质子交换膜燃料电池（PEMFC）中的氧还原反应（ORR）。点缺陷（空位）、平面缺陷（位错和晶界）和体缺陷（空隙、孔隙）可能在基于Pt和过渡金属的合金或核@壳纳米材料中产生，这是由于两种元素之间的高晶格失配。在这里，我们报告的空心PtNi/C纳米粒子的形态和结构的轨迹在真空下，N2-H2或空气气氛下的热退火过程中，通过原位透射电子显微镜和同步辐射X射线衍射。我们的证据气氛依赖的重组动力学，这使我们能够合成一组催化剂具有相同的化学组成和元素分布，但不同的形态，晶粒尺寸和晶格应变。通过结合Rietveld和对分布函数分析和电化学测量的结果，我们证明了位于单个微晶之间的界面处的结构无序区域对于PEMFC设备的两个感兴趣的反应是高度活跃的：电化学COads氧化和ORR。这些结果揭示了基本光的结构缺陷对催化性能的纳米材料的影响，并应有助于更有效的ORR电催化剂的合理设计。
The catalytic performance of extended and nanometer-sized surfaces strongly depends on the amount and the nature of structural defects that they exhibit. However, whereas the effect of steps or adatoms may be unraveled with single crystals ("surface science approach"), implementing reproducibly in a controlled manner structural defects on nanomaterials remains hardly feasible. A case that deserves particular attention is that of bimetallic nanomaterials, which are used to catalyze the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFC). Point defects (vacancies), planar defects (dislocations and grain boundaries), and bulk defects (voids, pores) are likely to be generated in alloy or core@shell nanomaterials based on Pt and a transition metal due to the high lattice mismatch between the two elements. Here, we report the morphological and structural trajectories of hollow PtNi/C nanoparticles during thermal annealing under vacuum, N-2 H-2 or air atmosphere by in situ transmission electron microscopy and synchrotron X-ray diffraction. We evidence atmosphere dependent restructuring kinetics, which enabled us to synthesize a set of catalysts with identical chemical compositions and elemental distributions but different morphologies, crystallite sizes, and lattice strain. By combining the results of Rietveld and pair-distribution function analyses and electrochemical measurements, we demonstrate that the structurally disordered areas located at the interface between individual crystallites are highly active for two reactions of interest for PEMFC devices: the electrochemical COads oxidation and the ORR. These results shed fundamental light on the effect of structural defects on the catalytic performance of bimetallic nanomaterials and should aid in the rational design of more efficient ORR electrocatalysts.