A homogeneous grain-controlled ScSZ functional layer for high performance low-temperature solid oxide fuel cells

Abstract

Scandia-stabilized zirconia (ScSZ) is employed as a cathodic functional layer onto yttria-stabilized zirconia based fuel cell systems for low-temperature solid oxide fuel cells.

Atomic layer deposition of GDC cathodic functional thin films for oxide ion incorporation enhancement

“…Although the total thickness of the electrolyte increases due to insertion of the ALD GDC functional layer, there is no significant difference in the size of the first semi-circle. 22 This result is due to both the relatively small (~50 nm) thickness increment resulting from addition of ALD GDC compared to total YSZ thickness as shown in Figure 9A-B and the relatively high ionic conductivity of doped-ceria materials (over an order of magnitude higher) compared to YSZ. 1,7 Thus, there was a negligible increase of ionic transport resistance and a significant decrease of electrode/electrolyte interface resistance when the ALD GDC functional layer was applied.…”

“…Figure 10B shows a significant decrease of electrode/electrolyte interface resistance in the sample using ALD GDC, while the ionic transport resistance was essentially unchanged. Although the total thickness of the electrolyte increases due to insertion of the ALD GDC functional layer, there is no significant difference in the size of the first semi‐circle 22 . This result is due to both the relatively small (~50 nm) thickness increment resulting from addition of ALD GDC compared to total YSZ thickness as shown in Figure 9A‐B and the relatively high ionic conductivity of doped‐ceria materials (over an order of magnitude higher) compared to YSZ 1,7 .…”

“…Grain boundary at the surface has been known as a favorable site for oxygen ion incorporation, and there has been researches that investigate this characteristic 19,20 . Also, Hong et al reported that a grain‐controlled layer (GCL), which is a layer with well‐developed grains, enhanced the performance even when the material for GCL was the same as the main electrolyte 21,22 . These researches demonstrated that it is important to fabricate thin films with high grain boundary density for improvement of the functional layer characteristics.…”

Grain-Controlled Gadolinia-Doped Ceria (GDC) Functional Layer for Interface Reaction Enhanced Low-Temperature Solid Oxide Fuel Cells

“…Unfortunately, this was not beneficial for suppressing defects such as pinholes, which were generated on the porous supporting structure. Some studies recently demonstrated that the columnar grain growth of thin-film electrolyte with sputtering can be reduced, resulting in sufficiently dense, pinhole-free films even when deposited on porous AAO substrates. ,,, …”

“…In addition, the activation energies of doped-ceria materials (<0.8 eV) were less than zirconia-based systems (>1.0 eV). ,− ,,, Therefore, doped-ceria systems are usually adopted as a cathode functional layer located between the cathode and electrolyte to facilitate the ORR. Most studies successfully demonstrated enhanced ORR kinetics resulting in high performance TF-SOFCs, but they only focused on the high ionic conductivity of the material. − Some recent works showed that the surface grain boundary density of thin-film electrolytes is strongly related to the surface oxygen incorporation rate. ,,,,− Specifically, they showed that the grain boundary has more oxygen vacancies than the grain interior due to intrinsic material property and the segregation of dopant, which helps oxygen ion incorporation.…”