Fuel Cell and Electrolysis Operation of Solid Oxide Cells Containing 3D-Printed Electrode Supports in H_2/H_2o and CO/CO_2 Gas Mixtures

摘要

Electrolysis of CO_2 using solid oxide cells is important both for renewable energy storage technologies as well as for upcoming, flagship space missions. Nevertheless, the performance of solid oxide cells operating for CO_2 electrolysis is generally diminished compared to an identical cell performing H_2O electrolysis. The reduced performance when operating in CO_2 results both from slower reaction kinetics as well as slower gas transport, which manifest in the performance as large activation and concentration polarizations, respectively. The finite diffusivity of both H_2/H_2O and CO/CO_2 gas mixtures leads to concentration losses which limit overall fuel cell or electrolysis performance, particularly at high current densities. Performance can be improved by diminishing the thickness of the porous electrode support layers, hence decreasing the gas diffusion distance between the flow channels and electrochemically active sites, but this also limits the mechanical support provided to the cell. Structured support layers which cover only some of the electrode functional layer potentially allow substantial areas of the cell to be very thin, hence easing gas transport from the flow channels to the electrochemically active sites, while largely maintaining the mechanical support for the cell. However, fabricating these layers out of SOC-relevant materials (such as Ni-YSZ) and incorporating them with the functional layers of the cell can be challenging.