Rhombohedral Ordered Intermetallic Nanocatalyst Boosts the Oxygen Reduction Reaction
Rhombohedral Ordered Intermetallic Nanocatalyst Boosts the Oxygen Reduction Reaction
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DOI：
10.1021/acscatal.0c04021
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发表时间：
2020-12
期刊：
影响因子：
12.9
通讯作者：
Xueru Zhao;H. Cheng;Lianghao Song;Lili Han;Rui Zhang;Gihan Kwon;Lu Ma;S. Ehrlich;A. Frenkel-A.
中科院分区：
文献类型：
--
作者：
Xueru Zhao;H. Cheng;Lianghao Song;Lili Han;Rui Zhang;Gihan Kwon;Lu Ma;S. Ehrlich;A. Frenkel-A.
低铂族金属（PGM）有序金属间化合物催化剂被认为是催化燃料电池中氧还原反应（ORR）的最有前途的候选者之一，但在活性、耐久性和成本方面实现期望的性能仍然是燃料电池研究领域的巨大挑战。虽然已经广泛研究了菱形和四方有序（L12和L10相）低PGM纳米催化剂，并且已经显示出显著改善的耐久性和对ORR的活性，但到目前为止，对菱形有序L11催化剂知之甚少。我们报告的L11有序PtCu催化剂的ORR的合成。我们证明，通过在NH3气体中热处理来施加氮（N）掺杂，可以进一步增强N掺杂的菱形有序PtCu催化剂的活性和稳定性，并且相对于商业Pt/C，在酸性介质中的ORR质量和比活性分别实现近5倍和4倍的增强。原位同步辐射X射线吸收和对分布函数的测量表明，形成有序的金属间结构和N-掺杂协同提高耐腐蚀性的PtCu催化剂，通过降低Cu的扩散系数，并引入压缩应变效应调节含氧物种在Pt表面上的吸附，从而占改善的ORR动力学。
Low platinum-group-metal (PGM) ordered intermetallic catalysts have been considered one of the most promising candidates for catalyzing the oxygen reduction reaction (ORR) in fuel cells, but achieving the desired performances in terms of activity, durability, and cost is still a grand challenge for the fuel cell research field. While the cubicand tetragonal-ordered (L12 and L10 phases) low-PGM nanocatalysts have been investigated extensively and have shown considerably improved durability and activity toward the ORR, so far, little is known about rhombohedral ordered L11 catalysts. We report the synthesis of an L11-ordered PtCu catalyst for the ORR. We demonstrate that by applying nitrogen (N) doping through a thermal treatment in an NH3 gas, the activity and stability of the N-doped, rhombohedral ordered PtCu catalyst can be further enhanced, and the ORR mass and specific activities achieve nearly 5-fold and 4-fold enhancement in acidic media, respectively, relative to those of commercial Pt/C. In situ synchrotron X-ray absorption and pair-distribution-function measurements reveal that both the formation of the ordered intermetallic structure and N-doping synergistically improve the corrosion resistance of the PtCu catalyst by lowering the Cu diffusivity and introduce a compressive strain effect regulating the adsorption of oxygenated species on the Pt surface, thus accounting for the improved ORR kinetics.