/johnny
Anyhow unless you were really desperate you would have no need to cook up your own lead sulfide. You’d have some on hand already. Besides you might come up with the wrong valence compound if you didn’t weigh your ingredients exactly enough, and it might fail to work as well as galena, if at all.
There were some interesting “liquid diode” designs used in the early detector days of radio before the vacuum tube came along. They involved things like brass wire dipped in nitric acid and proved reliable enough that they supplanted cat whiskers.