Can thin perovskite film materials be applied as model systems for battery applications?

The catalytic performance of carbon-based perovskite gas diffusion electrodes and thin films of identical perovskite catalyst phases (La0.6Ca0.4CoO3 d (LCCO), La0.7Ca0.3MnO3 d (LCMO) and La0.7Ca0.3Mn0.9Ni0.1O3 d (LCMNO)) has been compared. The thin films were deposited on MgO(1 0 0), MgO(1 1 0), and MgO(1 1 1) by pulsed reactive crossed-beam laser ablation (PRCLA). The quality of the films was determined by analyzing the composition as well as the crystallographic phase structure and texture of the electrodes. The catalytic activity for both the oxygen reduction and oxygen evolution reactions is evaluated from polarization curves for the selected electrodes. The compositional analysis of the films indicates that the ablation is congruent mainly for the LCCO, and that the films are nearly stoichiometric in their composition. The crystallographic orientation of the grown films is affected by the substrate. Under the selected deposition conditions it was not possible to grow parallel epitaxial films on MgO(1 1 0) and MgO(1 1 1). The key factors for epitaxy are besides the lattice misfit, also chemical/ electronic interactions between film and substrate. The predominant crystallographic orientation is the one corresponding to the next lower surface/interfacial energy. The prepared films act as bifunctional catalysts, and the electrochemical experiments indicate that different exposed surfaces affect the performance of the electrode. The most active electrode was found to be the (1 0 0) textured film.