Design of Highly Active Perovskite Oxides for Oxygen Evolution Reaction by Combining Experimental and ab Initio Studies

Perovskite oxides (ABO(3)) have recently attracted attention since tailoring their chemical compositions has resulted in remarkable activity toward oxygen evolution reaction (OER) which governs rechargeability of recently spotlighted metal-air batteries and regenerative fuel cells. For further development of highly OER active perovskite oxides, however, the exact mechanism the OER must be well understood. Herein, we introduce investigation of the OER mechanism of perovskite oxides by ab initio analysis based on well-defined model systems of LaMnO3 (LMO), LaCoO3 (LCO), and La0.5Sr0.5CoO3 (LSCO). In addition, we have systematically conducted electrochemical experiments from which we have observed an increasing trend in the OER activity in the order of LSCO > LCO > LMO based on the cyclic voltammetry (CV) results obtained in the alkaline medium. To validate the experimental results, free-energy diagrams have been constructed for oxygen intermediates on the surface of the defined models to find the limiting step by changing the B site atom (e.g., Mn and Co) and the partial displacement of Sr atoms in La site. The oxygen adsorption energy of perovskite oxides is found to increase with decreasing number of outer electrons as well as upshifting of the position of the d(z)(2) orbital toward the Fermi level of B site element. This work demonstrates that highly active OER perovskite oxides can be obtained by modifying the chemical composition to finely tune the oxygen adsorption energy on the catalysts surface, confirmed by synergetic approaches of using both experimental and ab initio computational studies.