Large Area Deposition by Radio Frequency Sputtering of Gd0.1Ce0.9O1.95 Buffer Layers in Solid Oxide Fuel Cells: Structural, Morphological and Electrochemical Investigation

Abstract

We investigate the influence of position, under large circular sputtering targets, on the final electrochemical performance of 35 mm diameter button solid oxide fuel cells with sputter-deposited Gadolinium doped Ceria barrier layers, positioned in order to almost cover the entirety of the area associated with a 120 × 80 mm2 industrial cell. We compare the results obtained via structural and morphological analysis to the Electrochemical Impedance Spectroscopy (EIS) measurements performed on the button cells, disentangling the role of different parameters. The Atomic Force Microscopy analysis makes it possible to observe a decrease in the roughness values from the peripheral to the central zones under the sputtering target, with peak-to-valley roughness values, respectively, decreasing from 380 nm to 300 nm, while Scanning Electron Microscopy and Energy Dispersive Spectroscopy show a dependence of the layer coverage from the position. The electrochemical performances of button cells with buffer layers of only 200 nm in thickness, and with negligible thickness gradients across them, show current density values of up to 478 mA/cm2 at 0.8 V and 650 °C, with an improvement of more than 67% with respect to button cells with standard (screen printed) buffer layers. These results point out the major influence exerted by parameters such as the thickness gradient and the coverage of the sputtered buffer layers in determining the final electrochemical performances.

Electrochemical Impedance Spectroscopy of Core‐Shell Nanofiber Cathodes, with Ce0.9Gd0.1O1.95 (Core) and Cu‐Doped La0.6Sr0.4MnO3 (Shell), for Application in Solid Oxide Fuel Cells

“…Finally, the polarization resistance R P is evaluated from the fittings as the difference between the low and high frequency intercepts of the Nyquist impedance spectra with the real axis. Furthermore, since this process can also be applied also to individual elements of the EC, a separate R P is defined for each EC element [23,42,44] …”

“…Furthermore, since this process can also be applied also to individual elements of the EC, a separate R P is defined for each EC element. [23,42,44]…”

Selection of Highlights of the European Project Next Generation Solid Oxide Fuel Cell and Electrolysis Technology – NewSOC

“…To check differences in the final electrochemical performances, the half cells were distributed under the sputtering target in order to almost cover the whole area associated to a standard (120x80 mm 2 ) fuel cell, figure 1a. The obtained j-V curves for different button cells are shown in figure 1b and compared to those measured on a cell with screen printed GDC layer (Reference sample) (17). Samples 1 and 2 clearly perform better than the reference one, with a 17 and 33 % increase in current density at 0.9 V and 650 °C, respectively.…”

Recent Advances and Challenges in Thin-Film Fabrication Techniques for Low-Temperature Solid Oxide Fuel Cells

“…However, decreasing the background pressure to relatively high vacuums (below 0.05 mbar) was shown to have a greater impact on the densification of the electrolyte film (Figure 10b), where the formation of fully dense films was reported at 0.026 mbar and 400 • C [327]. However, when comparing its electrical properties (for both YSZ and GDC thin films) with 10-30 µm films obtained by screen printing and spin coating, relatively higher activation energies and lower conductivities were observed for thin films prepared by the PVD method, mainly due to the loose connection between the electrolyte and the substrate, due to the surface roughness [327,328]. The substrate-target distance and their orientation have also been shown to play an important role in determining the morphology of the coated layer.…”