welcome @martinr and @jpengineering ! Iron hybrid RFBs are very appealing but managing hydrogen evolution is the real challenge---we've been working on some promising approaches here, Daniel has done some tests on a non-conventional iron electrolyte here: https://fbrc.nodebb.com/topic/44/only-fe-system.
I haven't seen Nighthawk's carbon felt video, but @rowow came through the forum already talking about his membranes! I'd like to get my hands on some to try (don't have the time right now to go into DIY membranes---we are using porous separators for the moment since they don't give us issues and we are mostly focused on cell/electrolyte R&D).
from this paper, seems like nanomaterial synthesis needed: https://www.nature.com/articles/s41560-026-02091-w#Sec25
also they use triflate salts --- that's likely more expensive than the Zn (and, fluorine-containing, with all that entails)
Time-stamping the electrolyte formulation for Zn-I, I am making the documentation to build the dev kit chemistry agnostic (so I am taking these weights out of the docs for now)
zinc chloride - 1.36 grams
potassium iodide - 3.32 grams
ammonium chloride - 1.07 grams
deionized water - 8.50 grams
triethylene glycol - 0.55 grams
This usually ends up preparing around 11 mL of solution which we split evenly between the two reservoirs.
