Date

2016-04-01

Author

Afal Geniş, Ayşegül
Aydınol, Mehmet Kadri

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Oxygen reduction reaction (ORR) catalytic activities have been of great scientific importance for extensive studies in energy storage technologies, specifically in metal-air batteries. Metal-air batteries are promising for future applications of especially electrical vehicles due to the utilization of oxygen from the air as one of the battery’s main components. Kinetic performance of the electrochemical reaction taking place in these batteries mainly depends on the reduction of oxygen at the cathode. Different groups of catalysts have been considered in order to facilitate ORR at the air electrodes including precious metal catalysts, metal oxides and carbons. Contrary to the ORR on metals and metal alloys in acidic environments, little is known about the influence of intrinsic properties of complex oxides on their activity toward the ORR in alkaline media. To develop novel and highly active cathode materials, a deeper understanding of the correlation between the cathode material properties and ORR activity is necessary. The crucial role of electronic structure in determining the electrochemical activity has been well recognized in the field of catalysis. First-principles computational studies, in particular density functional theory (DFT) studies, have made important contributions to such efforts, identifying fundamental correlations between catalytic activity and electronic structure for different types of catalyst materials. Therefore, ab initio methods become a useful tool to characterize catalytic properties by examining electronic structures, reaction energetics and activation energies. In this study, the effect of surface crystallography on oxygen molecule dissociation and adsorption properties on different types of transition metal perovskites of the type ABO3 (A=La, B= Mn, Cr, Fe, O=oxygen) are presented. To analyze the oxygen–perovskite interaction, ab initio molecular dynamics method is used to simulate the behavior of O2 at the surface. This method is expected to show whether the transition metal elements displayed an effect of catalyzer in terms of dissociation of the O2 molecule into O atoms at the surface. A systematical study within adsorption characteristics of oxygen on La-based perovskite surfaces was performed. In addition, via ab initio molecular dynamics simulations, what kind of an effect would different planes make on oxygen behavior at the surface was studied. Ab initio molecular dynamics simulations were executed on clean low- index (001) and (111) surfaces of perovskites. Simulations were done by ab initio pseudopotential method within the generalized gradient approximation (GGA) to density functional theory (DFT).

URI

https://hdl.handle.net/11511/84495

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Department of Metallurgical and Materials Engineering, Conference / Seminar