| Abstract | This chapter presents theoretical studies (mainly with first principle methods) of non-noble metal electrocatalysts for oxygen reduction reaction (ORR) in acid and alkaline PEM fuel cells. The focus is on fundamental understanding of effect of structure and properties of these electrocatalysts on oxygen reduction reaction mechanism and electrocatalytic activity. The chapter begins with a brief review of current understanding of oxygen reduction mechanism. The difference between ORR in acidic and alkali media is discussed. Four major types of non-nobel metal electrocatalysts are presented. These include transition metal N-macrocyclic complexes, heat-treated M-Nx/C, functionalized graphitic materials, and conducting polymers. Theoretical investigation of these electrocatalytic systems are presented and discussed; especially, the active site structures and electronic properties of electrocatalysts, adsorption configurations of oxygen and various ORR intermediates on electrocatlysts, energetics of possible reaction pathways, and effect of potentials on activity. These theoretical insights contribute greatly to our knowledge of the electrocatalytic systems and are invaluable for further development in this area. |
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