Tuning the Performance and the Stability of Porous Hollow PtNi/C Nanostructures for the Oxygen Reduction Reaction
Tuning the Performance and the Stability of Porous Hollow PtNi/C Nanostructures for the Oxygen Reduction Reaction
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DOI：
10.1021/acscatal.5b01248
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发表时间：
2015-09-01
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;Asset, Tristan;Maillard, Frederic
微孔和介孔材料由于具有较大的表面积体积比和分子可接近性，是电催化质子交换膜燃料电池（PEMFC）中的关键反应阴极氧还原反应（ORR）的一种很有前途的策略。在这里，我们合成并提供了多孔中空PtNi/C纳米催化剂的原子分辨率图像，研究了Ni和Pt原子的元素分布，测量了Pt晶格收缩，并将这些观察结果与它们的ORR活性相关联。最佳多孔空心Pt/C纳米催化剂的ORR质量和比活性分别比相同尺寸的标准固体Pt/C纳米晶体提高了6倍和9倍。与具有相似化学成分、Pt晶格收缩和晶粒尺寸的固体PtNi/C纳米晶体相比，催化增强的质量和比活性分别是前者的4倍和3倍。此外，在加速应力测试中，在0.60至1.00 V / RHE （0.1 M HClO4 T = 298 K）之间进行3万次电位循环后，最佳电催化剂在E = 0.90 V / RHE （0.56 A mg(-1) Pt）下的初始质量活性保持了100%，因此在质量活性和耐久性方面都达到了美国能源部2017-2020年的目标（0.44 A mg(-1) Pt，质量活性损失< 40%）。空心PtNi/C纳米催化剂具有较好的ORR催化活性，归因于(i)其开放的孔隙度，（ii）其优先的晶体取向（“系综效应”），以及（iii）收缩Pt晶格参数导致的氧结合能减弱（“应变效应”）。
Due to their increased surface area to volume ratio and molecular accessibility, microporous and mesoporous materials are a promising strategy to electrocatalyze the cathodic oxygen reduction reaction (ORR), the key reaction in proton-exchange membrane fuel cells (PEMFC). Here, we synthesized and provided atomically resolved pictures of porous hollow PtNi/C nanocatalysts, investigated the elemental distribution of Ni and Pt atoms, measured the Pt lattice contraction, and correlated these observations to their ORR activity. The best porous hollow PtNi/C nanocatalyst achieved 6 and 9-fold enhancement in mass and specific activity for the ORR, respectively over standard solid Pt/C nanocrystallites of the same size. The catalytic enhancement was 4 and 3-fold in mass and specific activity, respectively, over solid PtNi/C nanocrystallites with similar chemical composition, Pt lattice contraction, and crystallite size. Furthermore, 100% of the initial mass activity at E = 0.90 V vs RHE (0.56 A mg(-1) Pt) of the best electrocatalyst was retained after an accelerated stress test composed of 30 000 potential cycles between 0.60 and 1.00 V vs RHE (0.1 M HClO4 T = 298 K), therefore meeting the American Department of Energy targets for 2017-2020 both in terms of mass activity and durability (0.44 A mg(-1) Pt, mass activity losses < 40%). The better catalytic activity for the ORR of hollow PtNi/C nanocatalysts is ascribed to (i) their opened porosity, (ii) their preferential crystallographic orientation ("ensemble effect"), and (iii) the weakened oxygen binding energy induced by the contracted Pt lattice parameter ("strain effect").