Tailoring the Microstructure of a Solid Oxide Fuel Cell Anode Support by Calcination and Milling of YSZ

Abstract

In this study, the effects of calcination and milling of 8YSZ (8 mol% yttria stabilized zirconia) used in the nickel-YSZ anode on the performance of anode supported tubular fuel cells were investigated. For this purpose, two different types of cells were prepared based on a Ni-YSZ/YSZ/Nd2NiO4+δ-YSZ configuration. For the anode preparation, a suspension was prepared by mixing NiO and YSZ in a ratio of 65:35 wt% (Ni:YSZ 50:50 vol.%) with 30 vol.% graphite as the pore former. As received Tosoh YSZ or its calcined form (heated at 1500 °C for 3 hours) was used in the anode support as the YSZ source. Electrochemical results showed that optimization of the fuel electrode microstructure is essential for the optimal distribution of gas within the support of the cell, especially under electrolysis operation where the performance for an optimized cell (calcined YSZ) was enhanced by a factor of two. In comparison with a standard cell (containing as received YSZ), at 1.5 V and 800 °C the measured current density was −1380 mA cm−2 and −690 mA cm−2 for the cells containing calcined and as received YSZ, respectively. The present study suggests that the anode porosity for improved cell performance under SOEC is more critical than SOFC mode due to more complex gas diffusion under electrolysis mode where large amount of steam needs to be transfered into the cell.

The effect of pore-former morphology on the electrochemical performance of solid oxide fuel cells under combined fuel cell and electrolysis modes

“…However, the higher porosity of the cell as a result of using calcined YSZ leads to a decrease of the TPBs and the rate of electrochemical reactions in SOFC mode at the same time. The concentration polarization and activation polarization of the cell in this case seem to compensate each other and the fuel cell shows similar power performance to the cell which uses as-received YSZ in its anode [5].…”

“…It is known that the gas permeability, electrical conductivity and the rate of reaction in both SOFC and SOEC modes are highly dependent on the Ni-YSZ microstructure including the grain size of the nickel and YSZ phases, porosity and the percolation of each phase [5,6]. For example, it was shown by Han et al that decreasing the grain size of nickel led to an increased TPB length [7].…”

“…Regarding the differences between SOFC and SOEC modes, the higher steam content as well as the more difficult removal of hydrogen into the Ni-YSZ electrode in SOEC mode leads to M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 4 different microstructural requirements than SOFC mode [10]. As water molecules are more difficult to be transported due to their increased size in comparison with hydrogen molecules, the required porosity of Ni-YSZ for SOEC application is about 45%, while for SOFC mode it is about 35% [5,11].…”

A novel micro-solid oxide fuel cell ( $$\upmu $$ μ -SOFC) for detecting methane content in biogas

“…Figure 4c shows the microstructure of the cathode with ∼10 µm pin-holes. High porosity was observed from the microstructure of the cathode and anode [27]. Figure 4d shows the microstructure of the electrolyte with no pin-holes.…”

“…The GDC 10 powder was pressed to form pellets of 15 mm diameter and 2 mm thickness by using a uniaxial press under 3000 psi pressure. The GDC 10 pellet, as seen in figure 2a, was sintered at 1400 • C with a heating rate of 10 • C min −1 for 10 h. This GDC 10 pellet shows high density for ion conduction at high temperatures [27]. The 50:50 BYCF + GDC 10 cathode was deposited on the GDC 10 electrolyte pellet by SP in which the rectangular saw-tooth shape sticker covered the surface to control the shape of the cathode layer.…”