The stability of LaMnO3 surfaces: a hybrid exchange density functional theory study of an alkaline fuel cell catalyst

被引:25
作者
Ahmad, E. A. [1 ,2 ]
Mallia, G. [1 ,2 ]
Kramer, D. [1 ,3 ]
Kucernak, A. R. [1 ]
Harrison, N. M. [1 ,2 ,4 ]
机构
[1] Univ London Imperial Coll Sci Technol & Med, Dept Chem, London SW7 2AZ, England
[2] Univ London Imperial Coll Sci Technol & Med, Thomas Young Ctr, London SW7 2AZ, England
[3] Univ Southampton, Fac Engn & Environm, Southampton SO17 1BJ, Hants, England
[4] Daresbury Lab, STFC, Warrington WA4 4AD, Cheshire, England
基金
英国工程与自然科学研究理事会;
关键词
OXYGEN-REDUCTION ACTIVITY; METAL-AIR BATTERIES; NEUTRON-DIFFRACTION; LANTHANUM MANGANITE; CATHODE MATERIALS; OXIDE; PEROVSKITES; PERFORMANCE; PRINCIPLES; PREDICTION;
D O I
10.1039/c3ta11382e
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
LaMnO3 is an inexpensive alternative to precious metals (e. g. platinum) as a catalyst for the oxygen reduction reaction in alkaline fuel cells. In fact, recent studies have shown that among a range of non-noble metal catalysts, LaMnO3 provides the highest catalytic activity. Despite this, very little is known about LaMnO3 in the alkaline fuel cells environment, where the orthorhombic structure is most stable. In order to understand the reactivity of orthorhombic LaMnO3 we must first understand the surface structure. Hence, we have carried out calculations on its electrostatically stable low index surfaces using hybrid-exchange density functional theory, as implemented in CRYSTAL09. For each surface studied the calculated structure and formation energy is discussed. Among the surfaces studied the (100) surface was found to be the most stable with a formation energy of 0.98 J m(-2). The surface energies are rationalised in terms of the cleavage of Jahn-Teller distorted Mn-O bonds, the compensation of undercoordination for ions in the terminating layer and relaxation effects. Finally, the equilibrium morphology of orthorhombic LaMnO3 crystals is predicted, allowing us to speculate about likely surface reaction sites.
引用
收藏
页码:11152 / 11162
页数:11
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