Implementing Structural Disorder as a Promising Direction for Improving the Stability of PtNi/C Nanoparticles
Implementing Structural Disorder as a Promising Direction for Improving the Stability of PtNi/C Nanoparticles
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DOI：
10.1021/acscatal.7b00410
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发表时间：
2017-04-01
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
由于它们增强的氧还原反应（ORR）动力学（ORR的比活性和质量活性相对于商业Pt/C催化剂分别增强9倍和6倍），中空PtNi/C纳米颗粒吸引了越来越多的兴趣。这种催化增强产生于应变和配体效应的协同组合，结构缺陷的存在，以及它们的中空形态产生凸形和凹形催化位点。然而，在实际的质子交换膜燃料电池（PEMFC）阴极操作条件下，防止铂与其他过渡金属的合金（PtM合金，M是过渡金属）或富M核@富Pt壳纳米颗粒的催化活性损失仍然具有高度挑战性。性能的损失通常被观察到，因为在PEMFC阴极的苛刻的操作条件下的Pt和M的溶解，但是对于其中催化活性不仅仅是由于合金化效应的纳米材料，这个问题仍然没有答案。在此，我们仔细研究了在加速应力测试模拟PEMFC阴极操作过程中，具有相同化学组成但不同纳米结构的实心和空心PtNi/C纳米颗粒的ORR活性的变化。通过结合化学，物理和电化学技术，我们表明，镍原子的溶解构成的ORR催化活性的损失的主要原因，但在固体PtNi/C纳米粒子的中空的初始催化优势，保持在长期。因此，在PEMFC阴极电催化剂中实施结构无序代表了可持续地改善ORR动力学的有希望的方向。
Because of their enhanced oxygen reduction reaction (ORR) kinetics (9 and 6 -fold) enhancement of specific activity and mass activity for the ORR relative to those of a commercial Pt/C catalyst, respectively), hollow PtNi/C nanoparticles are attracting a growing level of interest. This catalytic enhancement arises from the synergetic combination of strain and ligand effects, the presence of structural defects, and their hollow morphology producing a convex and concave catalytic sites. However, preventing a loss of catalytic activity under practical proton exchange membrane fuel cell (PEMFC) cathode operating conditions on alloys of platinum with other transition metals (PtM alloys, M being a transition metal) or M-rich core@Pt-rich shell nanoparticles remains highly challenging. A loss of performance is usually observed because of the dissolution of Pt and M under the harsh operating conditions of a PEMFC cathode, but the question remains unanswered for nanomaterials in which catalytic activity is not solely due to alloying effects. Herein, we have carefully investigated the changes in the ORR activity of solid and hollow PtNi/C nanoparticles with identical chemical compositions but different nanostructures during an accelerated stress test simulating PEMFC cathode operation. By combining chemical, physical, and electrochemical techniques, we show that the dissolution of Ni atoms constitutes the primary reason for the loss of ORR catalytic activity but that the initial catalytic advantage of hollow over solid PtNi/C nanoparticles is maintained in the long term. Hence, implementing structural disorder in PEMFC cathode electrocatalysts represents a promising direction for sustainably improving ORR kinetics.