The Sulphur Poisoning Behaviour of Gadolinia Doped Ceria Model Systems in Reducing Atmospheres

Abstract

An array of analytical methods including surface area determination by gas adsorption using the Brunauer, Emmett, Teller (BET) method, combustion analysis, XRD, ToF-SIMS, TEM and impedance spectroscopy has been used to investigate the interaction of gadolinia doped ceria (GDC) with hydrogen sulphide containing reducing atmospheres. It is shown that sulphur is incorporated into the GDC bulk and might lead to phase changes. Additionally, high concentrations of silicon are found on the surface of model composite microelectrodes. Based on these data, a model is proposed to explain the multi-facetted electrochemical degradation behaviour encountered during long term electrochemical measurements. While electrochemical bulk properties of GDC stay largely unaffected, the surface polarisation resistance is dramatically changed, due to silicon segregation and reaction with adsorbed sulphur.

Evaluation of the Effect of Sulfur on the Performance of Nickel/Gadolinium‐Doped Ceria Based Solid Oxide Fuel Cell Anodes

“…However, they also mention that above 500 °C sulfur could diffuse into bulk ceria to lower the surface coverage, which could possibly give rise to long‐term degradation effects. The incorporation of sulfur into the CGO10 bulk phase at 10 ppm H 2 S exposure was also shown recently to be higher at increased temperatures by using time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) . In the present study, by using energy‐dispersive X‐ray spectroscopy (EDX), we were not able to detect any traces of sulfur postmortem.…”

“…The incorporation of sulfur into the CGO10b ulk phase at 10 ppm H 2 Se xposure was also shown recently to be higher at increased temperatures by using time-of-flight secondary ion mass spectrometry (TOF-SIMS). [63] In the presents tudy,b y using energy-dispersive X-ray spectroscopy (EDX), we were not able to detect any traces of sulfur postmortem.T horough long-term experiments will be required to shed more light on the sulfur-CGOi nteractionsi nS OFC operation.…”

The Relation of Microstructure, Materials Properties and Impedance of SOFC Electrodes: A Case Study of Ni/GDC Anodes

“…where ASR surf is the GDC area-specific resistance normalized to the surface area of GDC. Its value can be measured by impedance spectroscopic studies of dense thin film model electrodes [18,44,45]. When oxygen anions are released into the gas phase in the form of H 2 O (Equation (1)), the ionic current is converted to electron current.…”

Interaction of a ceria‐based anode functional layer with a stabilized zirconia electrolyte: Considerations from a materials perspective

“…The sulfur atoms show a propensity towards deposition at the three‐phase boundaries (TPB) in the anode, leading to a fast performance degradation, while massive coking can block the gas diffusion in the anode substrate in addition to blocking the TPBs. To improve the stability toward sulfur poisoning and cooking, Ni–GDC anodes have been suggested . Since a fraction of Ce 4+ ions reduce to Ce 3+ ions in the fuel gas, the electronic conductivity of GDC under anode conditions extends the TPBs and increases the active area of the anode, mitigating the effect of coking and sulfur deposition.…”

“…To improve the stability toward sulfur poisoning and cooking, Ni-GDC anodes have been suggested. [8][9][10][11][12] Since a fraction of Ce 4+ ions reduce to Ce 3+ ions in the fuel gas, the electronic conductivity of GDC under anode conditions extends the TPBs and increases the active area of the anode, mitigating the effect of coking and sulfur deposition.…”