Atomistic Explanation of the Dramatically Improved Oxygen Reduction Reaction of Jagged Platinum Nanowires, 50 Times Better than Pt
Atomistic Explanation of the Dramatically Improved Oxygen Reduction Reaction of Jagged Platinum Nanowires, 50 Times Better than Pt
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DOI：
10.1021/jacs.9b13218
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发表时间：
2020-05-13
影响因子：
15
通讯作者：
Goddard, William A., III
中科院分区：
文献类型：
--
作者：
Chen, Yalu;Cheng, Tao;Goddard, William A., III
Pt 是氧还原反应 (ORR) 的最佳催化剂，但速度太慢。 Huang 及其同事表明，脱合金 5 nm Ni7Pt3 纳米线 (NW) 会产生 2 nm 纯 Pt 锯齿状 NW (J-PtNW)，其 ORR 速度比 Pt/C 快很多倍。他们认为，表面 Pt 原子配位不足、机械应变和高电化学活性表面积 (ECSA) 是主要原因。我们在此报告多尺度原子模拟，从原子学角度进一步解释这种显着加速的 ORR 活动。我们使用 ReaxFF 反作用力场将 5 nm Ni7Pt3NW 转换为锯齿状 2 nm NW。我们应用量子力学发现，14.4% 的表面位点对于 O-ads + H2Oads -> 20H(ads)（速率决定步骤 (RDS)）是无障碍的。原因是许多表面位点的凹面性质推动了 H2Oads 的 OH 键，使其靠近 O-ads，从而导致势垒显着降低。我们利用这一观察结果来预测 J-PtNW 相对于 Pt (111) 的性能改进。假设每个表面位点都按照这个预测速率独立反应，则在 298.15 K 时会产生 212 倍的增强，而实验上是 50 倍。活性位点的原子结构为设计 ORR 高性能电催化剂提供了见解。
Pt is the best catalyst for the oxygen reduction reactions (ORRs), but it is far too slow. Huang and co-workers showed that dealloying 5 nm Ni7Pt3 nanowires (NW) led to 2 nm pure Pt jagged NW (J-PtNW) with ORRs SO times faster than Pt/C. They suggested that the undercoordinated surface Pt atoms, mechanical strain, and high electrochemically active surface area (ECSA) are the main contributors. We report here multiscale atomic simulations that further explain this remarkably accelerated ORR activity from an atomistic perspective. We used the ReaxFF reactive force field to convert the 5 nm Ni7Pt3NW to the jagged 2 nm NW. We applied quantum mechanics to find that 14.4% of the surface sites are barrierless for O-ads + H2Oads -> 20H(ads), the rate- determining step (RDS). The reason is that the concave nature of many surface sites pushes the OH bond of the H2Oads, close to the O-ads leading to a dramatically reduced barrier. We used this observation to predict the performance improvement of the J-PtNW relative to Pt (111). Assuming every surface site reacts independently with this predicted rate leads to a 212-fold enhancement at 298.15 K, compared to 50 times experimentally. The atomic structures of the active sites provide insights for designing high-performance electrocatalysts for ORR.