Methanol Fueled Low Temperature Solid Oxide Fuel Cell with Pt-SDC Anodes

Abstract

A low-temperature solid oxide fuel cell (LT-SOFC) is a next-generation energy conversion device and has advantages of high energy efficiency, fast start up and shut down and eco-friendliness. In addition, since it has the advantage of being able to use various fuels such as hydrogen, alcohol, and methane gas, research is being actively conducted in recent years. However, LT-SOFC using hydrogen as a fuel has difficulties in storing and transporting fuel, making it difficult to apply as a portable device. On the other hand, methanol fuel is an attractive alternative fuel because it is easier to transport and store than hydrogen fuel and has a high volumetric energy density. However, when methanol is applied to LT-SOFC, there is a disadvantage in performance due to the complicated oxidation process and CO poisoning. Complex methanol oxidation reaction (MOR) and CO poisoning reduce the performance and durability of fuel cells. Therefore, it is important to use a catalyst that can prevent CO poisoning and improve the oxidation reaction of methanol. Pt is an effective catalyst for methanol decomposition and is one of the materials widely used in direct methanol fuel cell (DMFC). However, there is a problem in that it is vulnerable to CO generated during the methanol oxidation process. It is known that CO is adsorbed on the Pt surface, blocks the active site, and reduces catalytic activity. Therefore, alloying Pt with samaria-doped ceria (SDC) with high oxygen storage capacity (OSC) and good OH generation capacity can be effective to reduce CO poisoning and coking.In this study, we prepared the cells with Pt-SDC cermet anodes with the Pt volume percent of 69 (Pt 0.69), 83 (Pt 0.83), 92 (Pt 0.92), and 95 (Pt 0.95) volume% by varying Pt and SDC powers in the co-sputtering process. In the electrochemical impedance spectroscopy (EIS), ohmic resistance was similar between all samples; on the other hand, activation resistance was measured to be 24.0, 19.5, 31.8, 30.8, and 53.0 Ω∙cm2 at Pt 0.69, Pt 0.83, Pt 0.92, Pt 0.95, and Pt 1 samples, respectively, confirming the lowest activation resistance at Pt 0.83. We speculate that the MOR is improved by the increase of triple phase boundary (TPB) sites and the facilitation of bifunctional CO oxidation mechanisms with higher content of SDC up to 17 mol% (Pt 0.83). However, in the anode with excessive SDC content (31 mol%, Pt 0.69), the Pt is oxidized to form PtO2, lowering the catalytic activity.