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The oxygen reduction reaction (ORR) is a critical process in energy conversion systems, influencing the efficiency and performance of various devices such as fuel cells, batteries, and electrolyzers. Perovskite-supported metal materials (metal/perovskite) offer several advantages as ORR electrocatalysts, including strong metal-support interactions, oxygen vacancy formation in the perovskite lattice, and synergistic triple-phase boundary (TPB) activity at the interface. Despite their significance, the mechanistic understanding of ORR on metal/perovskite catalysts remains incomplete, particularly at metal/perovskite interfaces. This study investigates ORR on BaZrO3 (BZO) perovskite-supported metal clusters (Pt or Ag) using density functional theory (DFT) to unravel critical insights into charge redistribution at the metal/BZO interface. Energy profiles for elemental steps along two different ORR pathways—oxygen adsorption on the metal cluster surface and direct oxygen adsorption at the TPB—were calculated to explore the effects of different active sites. The results provide a deeper understanding of ORR on metal/perovskite catalysts, emphasizing the role of interfacial interactions and pathway-dependent reaction mechanisms. This work paves the way for guiding the design of high-performance electrocatalysts for ORR in terms of composition, interface design, and local environment modification for a broad range of energy applications. 

BaCo0.4Fe0.4Zr0.1Y0.1O3−σ (BCFZY) is a proton, oxygen-ion, and electron-hole conducting cathode material for intermediate temperature solid oxide fuel cells. Its electrode reaction mechanism in air with moisture is not well understood. In this study, three types of symmetrical cells with the same BCFZY cathode were fabricated over three related proton conducting electrolytes: BaZr0.8−xCexY0.1Yb0.1O3−δ (x = 0.1, 0.4, and 0.7). The cathode shows similar performance over three different electrolytes in dry air but different responses to moisture introduction. The differences are hypothesized to relate to the mutual diffusion at the cathode/electrolyte interface. Such a hypothesis is supported by different techniques such as XRD Rietveld refinement of BCFZY cathode in mixtures with different electrolytes after firing, energy-dispersive X-ray spectroscopy (EDS) line scanning for element concentration distribution at the cathode/electrolyte interface, as well as electrochemical test for a related BaCoFeO-type cathode with Zr replaced by Ce.