高性能Pt 3 Sn合金催化剂在氧还原反应中的DFT研究,Computational Materials Science

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高性能Pt 3 Sn合金催化剂在氧还原反应中的DFT研究
Computational Materials Science ( IF 3.3 ) Pub Date : 2018-06-01 , DOI: 10.1016/j.commatsci.2018.03.014
Xiujun Wang , Xiaojiang Li , Shijun Liao , Baitao Li

摘要氧还原反应（ORR）是燃料电池阴极发生的多步催化过程。作为传统铂催化剂的替代品，与纯 Pt 催化剂相比，PtSn 基合金催化剂在实验上表现出增强的 ORR 活性。然而，ORR 反应如何在 PtSn 上进行尚不清楚。在此背景下，基于周期密度泛函理论 (DFT) 计算，系统研究了 Pt3Sn (1 1 1) 面的 O2 还原。随着电荷从 Sn 转移到 Pt，d 带中心远离费米能级，电子结构与纯 Pt 完全不同，从而产生配体（电子）效应。ORR 中间体（H、O、OH、O2、OOH、H2O2 和 H2O）物种优选位点、吸附构型、结合能、活性势垒、研究了速率常数、平衡常数。此外，使用爬升图像轻推弹力带（CI-NEB）方法确认了七个基本反应中相应的过渡态，并评估了每个反应步骤中的热力学和动力学性质。在此，DFT 结果表明，在 Pt3Sn(1 1 1) 和 Pt(1 1 1) 表面上，ORR 遵循 OOHad 解离途径（O2ad → OOHad → Oad → OHad → H2Oad）共享相同的机制。发现 (1 1 1) 表面上 ORR 的速率决定步骤是 Oad 氢化反应，该反应需要 Pt3Sn(1 1 1) 表面上 0.66 eV 的活化势垒和纯 Pt(1 1) 表面上 0.77 eV 1) 表面，表明 Sn 的引入显着降低了活化能垒。同样的温度，ORR在Pt3Sn(1 1 1)表面的反应速率比在纯Pt(1 1 1)表面快。我们的热力学和动力学结果验证了锡在提高 ORR 催化活性方面的重要作用。

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DFT study of high performance Pt 3 Sn alloy catalyst in oxygen reduction reaction

Abstract The oxygen reduction reaction (ORR) is a multi-step catalytic process occurring at the cathode in fuel cells. As an alternative to a conventional Platinum catalyst, PtSn-based alloy catalyst experimentally presents an enhanced ORR activity compared with pure Pt catalysts. However, how the ORR reaction proceeds on PtSn is not yet well understood. On this context, a systematic study of O2 reduction on the (1 1 1) facets of Pt3Sn based on periodic density functional theory (DFT) calculation is presented. With the charge transfer from Sn to Pt, d-band center shifts away from the Fermi level, the electronic structure thoroughly differs from that of pure Pt thus producing ligand (electronic) effect. The ORR intermediates (H, O, OH, O2, OOH, H2O2, and H2O) species preferred site, adsorption configuration, binding energies, active barriers, rate constants, equilibrium constant are studied. Additionally, the corresponding transition states in seven elementary reactions are confirmed using the climbing image nudged elastic band (CI-NEB) method, and the thermodynamic and dynamic property in each reaction step are evaluated. Herein, the DFT results imply that on both the Pt3Sn(1 1 1) and Pt(1 1 1) surfaces, the ORR share the same mechanism following OOHad dissociation pathway (O2ad → OOHad → Oad → OHad → H2Oad). The rate-determining step of the ORR on the (1 1 1) surfaces is found to be the Oad hydrogenation reaction which requires activation barrier of 0.66 eV on the Pt3Sn(1 1 1) surface and 0.77 eV on the pure Pt(1 1 1) surface, indicating the introduction of Sn significantly decreases the activation energy barrier. As the same temperature, the reaction rate of ORR on the Pt3Sn(1 1 1) surface is faster than that on the pure Pt(1 1 1) surface. Our thermodynamic and kinetic results verify the important role of tin in improving the catalytic activity of ORR.

更新日期：2018-06-01

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