Fabrication and Characterization of High Performance Intermediate Temperature Alumina Substrate Supported Micro-Tubular SOFCs

Abstract

The central challenge of solid oxide fuel cell (SOFC) technology lies in how to achieve sufficient robustness and reliability while significantly reducing system and operating cost. This paper studied a novel alumina substrate supported micro-tubular SOFC with high performance at intermediate temperatures. An in-house built extrusion system in combination with modified phase-inversion method was used to fabricate micro-tubular alumina substrate with radially well-aligned micro-channel array. The gas permeability of such an alumina substrate reached 69.2 × 10 5 Lm −2 h −1 , approximately ten times that of the substrate with conventional microstructures. The addition of NiO (10 wt%) sintering aid significantly improved the bending strength of α-Al 2 O 3 substrate while forming NiAl 2 O 4 spinel phase in the substrate. Built upon the fabrication of alumina substrate, anode electrode and electrolyte layers were fabricated through dip-coating and sintering process alternatively. A porous barrier layer strategy was employed to inhibit NiO in the anode layer from diffusing into the substrate during high temperature sintering process. The resulting dense electrolyte layer and anode functional layer with the thickness of ∼10 μm and ∼20 μm were obtained respectively. The alumina substrate supported micro-tubular SOFC with material system NiO-SDC/SDC/PrBaCo 2 O 5+δ demonstrated the peak power density of ∼1420 mW cm −2 at 600 • C, which is among the best performance of SOFCs with the same material system in open literature. The novel micro-tubular cell also demonstrated excellent thermal cycling stability. By replacing the high-cost rare-earth anode material with low-cost alumina, the novel design not only significantly reduced the cost but also improved the robustness and reliability of SOFCs.

Fabrication and Characterization of Direct Methane Fueled Thin Film SOFCs Supported by Microchannel-Structured Microtubular Substrates

“…It has been confirmed in our early work that NiAl 2 O 4 remains chemical stability in a reducing atmosphere of wet hydrogen under 800 °C but is decomposed into Ni and α-Al 2 O 3 above 900 °C . To further examine chemical stability of NiAl 2 O 4 substrate in methane at elevated temperatures, the sintered substrates were first reduced in humidified hydrogen at 600 °C for 5 h, followed by treatment in dry methane for 10 h at 800 and 900 °C, respectively.…”

“…In this respect, direct hydrocarbon fueled SOFCs are highly desired, and oxygen ions from cathode side might be the only oxygen source that can be used to inhibit carbon deposition (e.g., oxidize surface carbons) without sacrificing SOFC performance. It is noteworthy that although TPB sites are uniformly distributed in a thick Ni-cermet anode electrode in anode-supported SOFCs, studies have shown that electrochemical reactions are mainly confined within a narrow range near anode/electrolyte interface or effective reaction zone. , In other words, oxygen ions from cathode side would be largely consumed by electrochemical oxidation of fuel species in this effective reaction zone. As long as oxygen ions are continuously supplied, carbon deposition could be completely inhibited in this region.…”

“…Alumina is selected as an anode substrate because of its inert catalytic property, low price, excellent chemical and mechanical stability both in redox atmosphere, and at high temperatures. Alumina substrate is featured with well-aligned microchannels and open at inner surface, enabling facile fuel/gas diffusion . This strategy is different from anode buffer layer design in that the latter intentionally resists fuel/gas diffusion .…”

Fabrication and Characterization of Thin-Film SOFC Supported by Microchannel-Structured Zirconia Substrate for Direct Methane Operation

“…According to the reactions (4) and ( 5), when 𝐶𝐻 concentration is relatively low while that of mobile 𝑂 near the TPB sites are relatively high, the full oxidation of 𝐶𝐻 would occur; in other extreme situations of high 𝐶𝐻 concentration and low concentration of mobile 𝑂 , the partial oxidation of 𝐶𝐻 could take place. We have experimentally demonstrated that the microtubular substrate with radially well-aligned microchannels facilitates facile gas diffusion and is able to obtain very high gas permeability [35,36]. Accordingly, sufficiently high 𝐶𝐻 concentration would be maintained in the anode functional layer.…”

“…The as-prepared slurry was de-aired for 10 min and then loaded into an in-house build spinneret extrusion system to obtain green microtubular substrate. The extrusion system and related extrusion process were detailed elsewhere [35][36][37]. The green substrate was sintered at 1100 o C in the air for 3hrs to achieve sufficient mechanical strength for subsequent functional layer coatings of NiO, NiO-Zr0.1SDC, YSZ, SDC, and LSCF sequentially.…”