Origin of the overpotential for oxygen reduction at a fuel-cell cathode
Origin of the overpotential for oxygen reduction at a fuel-cell cathode
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DOI：
10.1021/jp047349j
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发表时间：
2004-11-18
影响因子：
3.3
通讯作者：
Jónsson, H
中科院分区：
文献类型：
--
作者：
Norskov, JK;Rossmeisl, J;Jónsson, H
本文提出了一种基于电子结构计算的电化学过程反应中间体稳定性的计算方法。我们使用该方法结合详细的密度泛函计算，详细描述了Pt（111）上电化学氧还原反应的自由能景观作为施加偏压的函数。这使我们能够确定该反应中发现的过电位的来源。吸附的氧和羟基被发现是非常稳定的中间体，在接近平衡的电位，和计算的速率常数为活化的质子/电子转移到吸附的氧或羟基可以定量地解释所观察到的动力学。计算的氧和羟基吸附能的数据库的基础上，在大量的不同的过渡金属和贵金属的氧还原率的趋势可以占。还考虑了涉及质子/电子转移到吸附的分子氧的替代反应机制，并且发现这种过氧化物机制在大多数贵金属中占主导地位。该模型提出了改善燃料电池阴极电催化性能的方法。
We present a method for calculating the stability of reaction intermediates of electrochemical processes on the basis of electronic structure calculations. We used that method in combination with detailed density functional calculations to develop a detailed description of the free-energy landscape of the electrochemical oxygen reduction reaction over Pt(111) as a function of applied bias. This allowed us to identify the origin of the overpotential found for this reaction. Adsorbed oxygen and hydroxyl are found to be very stable intermediates at potentials close to equilibrium, and the calculated rate constant for the activated proton/electron transfer to adsorbed oxygen or hydroxyl can account quantitatively for the observed kinetics. On the basis of a database of calculated oxygen and hydroxyl adsorption energies, the trends in the oxygen reduction rate for a large number of different transition and noble metals can be accounted for. Alternative reaction mechanisms involving proton/electron transfer to adsorbed molecular oxygen were also considered, and this peroxide mechanism was found to dominate for the most noble metals. The model suggests ways to improve the electrocatalytic properties of fuel-cell cathodes.