Double Columnar Structure with a Nanogradient Composite for Increased Oxygen Diffusivity and Reduction Activity

Abstract

The cathodic performances that can be achieved in solid oxide fuel cells (SOFCs), particularly in terms of oxygen diffusion, need to be improved so that high power densities can be produced at intermediate temperatures. Here, to improve the cathodic performance, a double columnar functional interlayer (DCFL) consisting of Sm0.2Ce0.8O2−δ (SDC) and Sm0.5Sr0.5CoO3−δ (SSC) is fabricated between a La0.9Sr0.1Ga0.8Mg0.2O3−δ electrolyte film and a SSC cathode film with pulsed laser deposition. The DCFL has a rough surface morphology consisting of nanosized grains (with diameters less than 5 nm), and it is formed of small columns that grow at an angle of ca. 45° from the substrate. Inserting the DCFL causes the electrical conductivity of the cathode to increase significantly, and the power density obtained by using it in a metal‐supported SOFC is increased. Atomic resolution scanning transmission electron microscopy (TEM) images and density functional theory calculations confirm that the samarium atoms in the SDC columns and cobalt atoms in the SSC columns are located at the interfaces between SDC and SSC columns. Therefore, it is possible a SmCoO3−δ nanogradient is formed, which may cause lattice distortions. The 18O2 concentration is actually much higher in the DCFL than in either of SSC or SDC films.

Nanostructured Double Perovskite Cathode With Low Sintering Temperature For Intermediate Temperature Solid Oxide Fuel Cells

“…Nevertheless, the high operating temperatures of 800–1000 °C lead to critical problems including corrosion, chemical interdiffusion, reactions between components, and high thermal stress. In an effort to overcome these problems, intermediate‐temperature SOFCs (IT‐SOFCs) with an operating temperature range of 500–700 °C have been widely studied 1–5. The reduced operating temperature, however, gives rise to poor activity for the oxygen reduction reaction (ORR) at the cathode and consequently increases the polarization resistance ( R p ) of the cathode.…”

Nanomaterials for Advanced Electrode of Low Temperature Solid Oxide Fuel Cells (SOFCs)

“…Our group also studied a similar approach to increasing the cathodic activity. 12) In our study, nano size columnar Sm doped CeO 2 and Sm 0.6 Sr 0.4 CoO 3 were also prepared by PLD method under higher oxygen partial pressure. A high resolution transmission electron microscopy (TEM) image of the prepared double columnar structure is shown in Fig.…”

Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

“…Taken with permission from [31] by Ju et al, with one modification: scale bar labels have been enlarged in this version for clarity.…”

“…Using techniques such as pulsed laser deposition (PLD), it is possible to create thin film electrodes with controlled nano-architectures, exhibiting a high density of interfaces parallel to the direction of oxygen incorporation. In Figure 3 , one example of such an approach, named a “double columnar system” or sometimes “vertically aligned nanostructure (VAN)”, is shown schematically [ 31 ]. In this structure, nano-sized columns of Sm doped CeO 2 and Sm 0.6 Sr 0.4 CoO 3 have been deposited by the PLD method.…”

“…Figure 4 shows the power generation ability of a SOFC single cell with and without a double columnar interlayer between the electrolyte and porous oxygen electrode [ 31 ]. In this cell, a Ni-Fe metallic anode substrate, Sm doped CeO 2 buffer layer, La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 (LSGM) oxide electrolyte (500 μm thickness), and porous Sm 0.5 Sr 0.5 CoO 3 electrode were used.…”