In perovskites, exsolution of transition metals has been proposed as a smart catalyst design for energy applications. Although there exist transition metals with superior catalytic activity, they are limited by their ability to exsolve under a reducing environment. When a doping element is present in the perovskite, it is often observed that the surface segregation of the doping element is changed by oxygen vacancies. However, the mechanism of co-segregation of doping element with oxygen vacancies is still an open question. Here we report trends in the exsolution of transition metal (Mn, Co, Ni and Fe) on the PrBaMn2O5+δ layered perovskite oxide related to the co-segregation energy. Transmission electron microscopic observations show that easily reducible cations (Mn, Co and Ni) are exsolved from the perovskite depending on the transition metal-perovskite reducibility. In addition, using density functional calculations we reveal that co-segregation of B-site dopant and oxygen vacancies plays a central role in the exsolution.

A class of double-perovskite compounds display fast oxygen ion diffusion and high catalytic activity toward oxygen reduction while maintaining excellent compatibility with the electrolyte. The astoundingly extended stability of NdBa(1-x)Ca(x)Co2O(5+δ) (NBCaCO) under both air and CO2-containing atmosphere is reported along with excellent electrochemical performance by only Ca doping into the A site of NdBaCo2O(5+δ) (NBCO). The enhanced stability can be ascribed to both the increased electron affinity of mobile oxygen species with Ca, determined through density functional theory calculations and the increased redox stability from the coulometric titration.

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Surface decorated electrocatalytic nanoparticles coupled with oxide materials can effectively improve the electrochemical catalytic properties in energy storage and conversion application, such as chemical processes, electrolysis, batteries, and fuel cells. Particularly, Mn rich simple perovskite-type R 0.5 Ba 0.5 MnO 3-δ (R = Pr and Nd) undergoes a phase transition to layered perovskite RBaMn 2 O 5+δ at high temperature reduced condition. During this phase transition, the exsolution of MnO nanoparticles (MnO-NP) from the bulk layered perovskite NdBaMn 2 O 5+δ is observed. For in-depth investigation on the exsolution of MnO, a layered NdBaMn 2 O 5+δ thin film is fabricated with pulsed laser deposition and characterized by transmission electron microscopy. For the first time, this paper reports clear evidence of selfdecorated MnO nanoparticles on a layered NdBaMn 2 O 5+δ matrix via exsolution process and their electro catalytic effect in solid oxide fuel cells.

A new concept of an "oxygen shuttle" type battery for Mg-air solid oxide batteries using a Ca-stabilized ZrO2 electrolyte was proposed and studied. The observed open circuit potential and discharge capacity were 1.81 V and 1154 mA h gMg(-1) (52% of the theoretical capacity), respectively.

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