OOH结合位点和铂表面结构对氧还原反应活性的作用。
The Role of OOH Binding Site and Pt Surface Structure on ORR Activities.
作者信息
Jia Qingying, Caldwell Keegan, Ziegelbauer Joseph M, Kongkanand Anusorn, Wagner Frederick T, Mukerjee Sanjeev, Ramaker David E
机构信息
Department of Chemistry & Chemical Biology, Northeastern University, Boston, Massachusetts 02115, USA.
Department of Chemistry, George Washington University, Washington, DC 20052, USA.
出版信息
J Electrochem Soc. 2014;161(14):F1323-F1329. doi: 10.1149/2.1071412jes.
We present experimentally observed molecular adsorbate coverages (e.g., O(H), OOH and HOOH) on real operating dealloyed bimetallic PtM (M = Ni or Co) catalysts under oxygen reduction reaction (ORR) conditions obtained using X-ray absorption near edge spectroscopy (XANES). The results reveal a complex Sabatier catalysis behavior and indicate the active ORR mechanism changes with Pt-O bond weakening from the O dissociative mechanism, to the peroxyl mechanism, and finally to the hydrogen peroxide mechanism. An important rearrangement of the OOH binding site, an intermediate in the ORR, enables facile H addition to OOH and faster O-O bond breaking on 111 faces at optimal Pt-O bonding strength, such as that occurring in dealloyed PtM core-shell nanoparticles. This rearrangement is identified by previous DFT calculations and confirmed from in situ measured OOH adsorption coverages during the ORR. The importance of surface structural effects and 111 ordered faces is confirmed by the higher specific ORR rates on solid core vs porous multi-core nanoparticles.
我们展示了在氧还原反应（ORR）条件下，通过X射线吸收近边光谱（XANES）获得的实际运行的脱合金双金属PtM（M = Ni或Co）催化剂上实验观察到的分子吸附物覆盖度（例如，O(H)、OOH和HOOH）。结果揭示了一种复杂的Sabatier催化行为，并表明活性ORR机制随着Pt - O键从O解离机制减弱到过氧机制，最终到过氧化氢机制而发生变化。OOH结合位点（ORR中的一种中间体）的重要重排使得在最佳Pt - O键强度下，如在脱合金PtM核壳纳米颗粒中发生的那样，在111面上能够轻松地向OOH添加H并更快地断裂O - O键。这种重排通过先前的密度泛函理论（DFT）计算得到确定，并通过ORR期间原位测量的OOH吸附覆盖度得到证实。与多孔多核纳米颗粒相比，实心核纳米颗粒上更高的ORR比速率证实了表面结构效应和111有序面的重要性。
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