The stability of LaMnO3 surfaces: A hybrid exchange density functional theory study of an alkaline fuel cell catalyst
Publication date
2013-08-01
Document type
Research article
Author
Organisational unit
Department of Chemistry, Imperial College London
ISSN
Series or journal
Journal of materials chemistry A
Periodical volume
1
Periodical issue
37
First page
11152
Last page
11162
Peer-reviewed
✅
Part of the university bibliography
Nein
Abstract
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/m2. 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.
Version
Not applicable (or unknown)
Access right on openHSU
Metadata only access