Mixed ionic-electronic conducting oxides, such as the first Ruddlesden-Popper (R-P) series of layered oxides (A<sub>2</sub>BO<sub>4</sub>), have attracted increasing interest because of their high oxygen exchange ability that make them suitable for a number of electrocatalytic applications involving oxygen evolution and reduction. [1] Surface oxygen exchange is the process that governs oxygen reduction and evolution on these oxides. We have recently shown through a combination of quantum chemical density functional theory (DFT) calculations, controlled synthesis of well-defined nanostructures, state-of-the-art characterization techniques (atomic level imaging and electron energy loss spectroscopy), and isotopic labeling kinetic studies that the surface structure of these oxides plays a critical role on their surface oxygen exchange activity. [2] We found that (001) transition-metal oxide terminated oxide surface exhibited the highest rates for this process. Here, the effect of the A and B site composition on the electrocatalytic activity toward surface oxygen exchange is considered. DFT calculations showed that the surface oxygen exchange rates could be improved by varying the composition of the B-site (transition metal site). These predictions were supported by experimental studies. Nanostructured B-site doped nickelate oxides were synthesized and tested. [3] Among the oxides tested, Co-based R-P oxides exhibited the lowest barrier for surface oxygen exchange, consistent with our theoretical predictions. These findings pave away for utilization of nanostructured nickelate oxides as non-precious metal based electrocatalysts for oxygen reduction and evolution.

Tuning the electrochemical activity of layered nickleate oxides for oxygen reduction: Effect of surface termination and composition

254th National Meeting (2017)

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