There can be a wall/wall-shadow between two fluid zones, this is not a problem. The fuel-module takes care of what's happening in between these two surfaces with some submodels without resolving the electrolyte explicitly. Please refer to the SOFC theory and user guide on what is happening there exactly.
We do have a comprehensive tutorial for the example that you showed in your post, including all relevant files. These files are available from Ansys Customer Portal (Solution 2067055) as well as from Ansys Learning Hub. I appreciate that you might not have access to them, but please check with your supervisor, who might have access. There is also a trial access to the Ansys Learning Hub for which you can apply.