(240c) Design of Non-Stochiometric Mixed Metal Oxides As Electrocatalysts for Oxygen Reduction

Oxygen reduction reaction (ORR) has attracted significant attention due to its critical role in the performance of electrochemical energy conversion and storage devices.^{1, 2} To date, Pt-based electrocatalysts exhibit the best performance for low temperature ORR, but are limited by high cost. Alternatively, non-precious metal based non-stoichiometric mixed metal oxides with mixed ionic and electronic conducting properties (i. e., perovskite-based oxides) have shown promise for this reaction in alkaline solution.^{3, 4} While promising, the underlying mechanisms and factors governing the activity and selectivity of ORR are still unclear due to the challenges of the surface structure control and characterization of these oxides, limiting the rational design of these materials with optimal performance. In this work, a combined density functional theory (DFT) calculations and experiments approach has been used to study the ORR on a series of nanostructured Ruddlesden–Popper (R-P) oxides in alkaline media. DFT studies are used to calculate the energetics associated with the elementary steps of ORR under reaction conditions as a function of the B-site composition. Changes in the binding strength of the intermediates leading to changes in the overall ORR activity and selectivity are found. The calculations were supported using electrochemical studies with well-controlled nanostructures of these oxides.

References

1. Gu, X. K.; Nikolla, E., ACS Catal. 2017, 7, 5912-5920.
2. Ma, X.; Carneiro, J. S. A.; Gu, X. K.; Qin, H.; Xin, H.; Sun, K.; Nikolla, E., ACS Catal. 2015, 5, 4013-4019.
3. Gu, X. K., Samira, S., Nikolla, E., Chem. Mater. 2018, DOI:10.1021/acs.chemmater.8b00694.
4. Suntivich, J.; Gasteiger, H. A.; Yabuuchi, N.; Nakanishi, H.; Goodenough, J. B.; Shao-Horn, Y., Nat. Chem. 2011, 3, 546-550.