Metal Supported Solid Oxide Fuel Cell Using Proton Conducting Electrolyte for Direct Ammonia Utilization

Abstract

Transportation represents about 27% of global warming greenhouse gas emissions nowadays. To reduce these emissions, fuel cell electric vehicles have been poised to be a new trend to provide zero-emission transportation. Among them, solid oxide fuel cells (SOFCs) offer efficient, clean energy, especially when powered by carbon-free fuel, such as ammonia. To enable onboard ammonia-fed SOFCs, a metal-supported, proton-conducting SOFC is investigated in this study. The metal support would provide physical robustness for thermal shock during vehicles’ quick start-up and shutdown, reduce internal temperature gradients due to the greater thermal conductivity of the metal, and enable conventional metal joining for easy manufacturing. The proton-conducting electrolyte avoids the mixing of O and N, only leads H to the air side for electrochemical reaction. This study is dedicated to overcoming the barriers in the fabrication of metal-supported H-SOFCs and innovating electrolyte and cathode materials for cutting-edge performance. Different metals, pore forms and processing procedures have been employed to achieve a robust, well-functioning metal-ceramic bilayer assembly. The composition of the Ba(ZrCeYYb)O3-based perovskite proton-conducting electrolyte has been particularly tuned to yield a high ionic conductivity at the presence of Ba evaporation and diffusion to metal support during high-temperature treatment. A H+, e, O2- triple conducting cathode is modified with surface infiltration to achieve excellent electrochemical catalytic activity at intermediate temperature. In the end, a Ni//BZCYYb//PNO metal-supported cell is successfully obtained. A peak powder density of 231 mW/cm2 is achieved at 650oC using ammonia directly, one of the best performances among the reported in the literature. These results bring us closer to the goal of more accessible and affordable technology for fuel cell-powered transportation.