Abstract
In electrode-supported solid oxide fuel cells (SOFCs) with a thin electrolyte, the electrolyte performance can be affected by its interaction with the electrode, therefore, it is particularly important to study the charge transport properties of thin electrode-supported electrolytes. The transport numbers of charged species in Ni-cermet supported Sr0.98Zr0.95Y0.05O3−δ (SZY) membranes were studied and compared to those of the bulk membrane. SZY films of 2.5 μm thickness were fabricated by the chemical solution deposition technique. It was shown that the surface layer of the films contained 1.5–2 at.% Ni due to Ni diffusion from the substrate. The Ni-cermet supported 2.5 μm-thick membrane operating in the fuel cell mode was found to possess the effective transport number of oxygen ions of 0.97 at 550 °C, close to that for the bulk SZY membrane (0.99). The high ionic transport numbers indicate that diffusional interaction between SZY films and Ni-cermet supporting electrodes does not entail electrolyte degradation. The relationship between SZY conductivity and oxygen partial pressure was derived from the data on effective conductivity and ionic transport numbers for the membrane operating under two different oxygen partial pressure gradients—in air/argon and air/hydrogen concentration cells.
Highlights
The growth of global energy consumption requires the development of effective energy conversion methods
The film fabricated via a multi-step chemical solution deposition and synthesized at 1000 ◦ C showed a nanograined morphology with grains of 100–200 nm
The bulk sample obtained by a soft chemistry route followed by sintering at 1650 ◦ C possessed a dense microstructure with grains of up to 4–5 μm
Summary
The growth of global energy consumption requires the development of effective energy conversion methods. Solid oxide fuel cells (SOFCs) are promising devices for the conversion of fuel energy to electricity with high efficiency and low environmental pollution [1,2]. SOFCs based on proton-conducting electrolytes offer significant advantages compared to those using oxygen ion conducting electrolytes. Among these benefits, a lower operating temperature due to an acceptable conductivity in the proton-conducting oxides at intermediate temperatures, and the ability to produce pure hydrogen on the hydrogen electrode avoiding the problem of fuel dilution by mixing with water, appear to be the most important ones. Reducing the operating temperature lowers the cost and enhances the durability and reliability of SOFCs [2,3]. The application of thin-film membranes for the development of portable powering microdevices is considered a significant part of an upcoming nanoionics revolution [4,5]
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