Abstract
This work deals with the effect of sulfur incorporation into model-type GDC thin films on their in-plane ionic conductivity. By means of impedance measurements, a strongly deteriorating effect on the grain boundary conductivity was confirmed, which additionally depends on the applied electrochemical polarisation. To quantify the total amount of sulfur incorporated into GDC thin films, online-laser ablation of solids in liquid (online-LASIL) was used as a novel solid sampling strategy. Online-LASIL combines several advantages of conventional sample introduction systems and enables the detection of S as a minor component in a very limited sample system (in the present case 35 μg total sample mass). To reach the requested sensitivity for S detection using an inductively coupled plasma-mass spectrometer (ICP-MS), the reaction cell of the quadrupole instrument was used and the parameters for the mass shift reaction with O2 were optimised. The combination of electrical and quantitative analytical results allows the identification of a potential sulfur incorporation pathway, which very likely proceeds along GDC grain boundaries with oxysulfide formation as the main driver of ion transport degradation. Depending on the applied cathodic bias, the measured amount of sulfur would be equivalent to 1–4 lattice constants of GDC transformed into an oxysulfide phase at the material's grain boundaries.
Highlights
Determination of S in bulk materials as well as in thin lms or nanomaterials is of increasing interest due to the wide variety of physical, optical, electrochemical, or mechanical properties of metal sul des, oxysul des, or oxides interacting with H2S containing atmospheres.[2,3,4] Usually, for all these functional materials, there is a strong link between elemental composition and the desired properties
Considering these results, we suggest the following tentative mechanism of sulfur incorporation into polycrystalline Gadolinium doped ceria (GDC) lms: for low H2S partial pressures and only moderately reducing atmospheres, sulfur rst penetrates the grain boundary core and only minute amounts of S diffuse into the GDC grains without causing a phase change
In this work the sulfur uptake into GDC thin lms from a H2S containing H2/H2O atmosphere was studied in dependence of the applied electrochemical polarisation
Summary
Determination of S in bulk materials as well as in thin lms or nanomaterials is of increasing interest due to the wide variety of physical, optical, electrochemical, or mechanical properties of metal sul des, oxysul des, or oxides interacting with H2S containing atmospheres.[2,3,4] Usually, for all these functional materials, there is a strong link between elemental composition and the desired properties. Gadolinium doped ceria (GDC) is a promising novel anode material for solid oxide fuel cells (SOFCs), with increased H2S poisoning resilience being one of its advantages. This bene t can be improved by using dopants[5,6] or tailored fabrication procedures to in uence the architecture of GDC thin lms.[7] Under certain conditions, the performance of GDC anodes degrades during operation with fuels containing
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