pesco - 19-12-2025 at 15:14
I was about to make a terracotta pot as membrane for electrochemical cell, but decided to look around before I get to the trouble.
And found something that ticks all the boxes - Smooth large clay candle / plant pot – 250ml
Large enough, no drainage hole and great shape, not the standard conical.
It is UK based online shop, but you might be able to find similar locally or on Temu.
Next thing to look for will be terracotta "plate" to fill window in divider in split cell 
Hexabromobenzene - 19-12-2025 at 15:59
Polypropylene composite anyway better
Varungh - 17-1-2026 at 07:11
I suggest you use polypropylene. Hexbromobenzene has done decent research on the topic. I am actually in process of seeing if I can tweak his design.
Currently I am trying polypropylene in a H Cell.
Polypropylene has the advantage of being resistant to basically anything. It can even survive peroxymonosulfuric acid.
Terracotta would work. I suggest you buy it if you accept a small contamination from the pot. It is cheap, big, easy to use and doesn't leak. If small
contamination is issue, I suggest checking Hexbromobenzene work on the topic