The role of nitrogen-doping and the effect of the pH on the oxygen reduction reaction on highly active nitrided carbon sphere catalysts
The role of nitrogen-doping and the effect of the pH on the oxygen reduction reaction on highly active nitrided carbon sphere catalysts
复制标题
DOI：
10.1016/j.electacta.2019.01.046
复制
发表时间：
2019-03-10
影响因子：
6.6
通讯作者：
Behm, R. J.
中科院分区：
文献类型：
--
作者：
Eckardt, M.;Sakaushi, K.;Behm, R. J.
为了更好地理解无金属催化剂上氧还原反应（ORR）的分子尺度机理，我们采用实验和理论相结合的方法，在一组氮化碳球催化剂上系统地研究了该反应。这些催化剂，这是类似的制备，但应用不同的碳化/氮化温度，在酸性和碱性电解液中进行了研究。通过透射电子显微镜（TEM）、N-2吸附、X射线光电子能谱（XPS）、CHN分析和能量色散X射线能谱（EDX）以及CO2的程序升温脱附（TPD）对本体材料和表面的物理性质进行表征。采用旋转环盘电极（RRDE）对催化剂的电化学性能进行了表征.使用氘代电解质（KOD和D2SO4），通过ORR的动力学分析和动力学同位素效应（H-D交换）的评价探索了机制方面。结合基于密度泛函理论的计算，这些动力学数据提供了详细的见解的反应机理及其对pH值的影响。在酸性电解质中，第一个质子偶联电子转移（PCET）被确定为速率决定步骤（RDS），而在碱性电解质中，第一个电子转移（ET）到O-2（ad）*（-）是速率决定步骤，随后是快速质子化。这些高活性催化剂的潜力和结构效应的影响进行了讨论。(C)2019爱思唯尔有限公司版权所有。
Aiming at a better understanding of the molecular scale mechanism of the oxygen reduction reaction (ORR) on metal-free catalysts, we have systematically investigated this reaction in a combined experimental and theoretical approach on a set of catalysts consisting of nitrided carbon spheres. These catalysts, which were prepared similarly, but applying different carbonization/nitriding temperatures, were studied in acidic and alkaline electrolyte. The physical properties characterization of both, the bulk materials and the surface, was performed by transmission electron microscopy (TEM), N-2 sorption, X-ray photoelectron spectroscopy (XPS), CHN analysis and energy dispersive X-ray spectroscopy (EDX) and Temperature Programmed Desorption (TPD) of CO2. Electrochemical and -catalytic properties were characterized by rotating ring disk electrode (RRDE) measurements. Mechanistic aspects were explored by kinetic analysis of the ORR and by evaluation of the kinetic isotope effect (H-D exchange), using deuterated electrolytes (KOD and D2SO4). In combination with density functional theory based calculations, these kinetic data provide detailed insights into the reaction mechanism and its dependence on pH effects. In acidic electrolyte, the first proton coupled electron transfer (PCET) is identified as rate determining step (RDS), while in alkaline electrolyte the first electron transfer (ET) to O-2 (ad)*(-) is rate determining, followed by fast protonation. The potential of these highly active catalysts and the influence of structural effects are discussed. (C) 2019 Elsevier Ltd. All rights reserved.