Optimizing Oxygen Reduction Catalyst Morphologies from First Principles

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• 作者：Ehsan A. Ahmad ; Vasiliki Tileli ; Denis Kramer ; Giuseppe Mallia ; Kelsey A. Stoerzinger ; Yang Shao-Horn ; Anthony R. Kucernak ; Nicholas M. Harrison
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：July 23, 2015
• 年：2015
• 卷：119
• 期：29
• 页码：16804-16810
• 全文大小：499K
• ISSN：1932-7455

文摘

Catalytic activity of perovskites for oxygen reduction (ORR) was recently correlated with bulk d-electron occupancy of the transition metal. We expand on the resultant model, which successfully reproduces the high activity of LaMnO₃ relative to other perovskites, by addressing catalyst surface morphology as an important aspect of the optimal ORR catalyst. The nature of reaction sites on low index surfaces of orthorhombic (Pnma) LaMnO₃ is established from First Principles. The adsorption of O₂ is markedly influenced by local geometry and strong electron correlation. Only one of the six reactions sites that result from experimentally confirmed symmetry-breaking Jahn鈥揟eller distortions is found to bind O₂ with an intermediate binding energy while facilitating the formation of superoxide, an important ORR intermediate in alkaline media. As demonstrated here for LaMnO₃, rational design of the catalyst morphology to promote specific active sites is a highly effective optimization strategy for advanced functional ORR catalysts.